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//===- Local.cpp - Functions to perform local transformations -------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This family of functions perform various local transformations to the
// program.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AssumeBundleQueries.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/DomTreeUpdater.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/MemorySSAUpdater.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Analysis/VectorUtils.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/IR/Argument.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/EHPersonalities.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/GlobalObject.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/IntrinsicsWebAssembly.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/MemoryModelRelaxationAnnotations.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/ProfDataUtils.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Use.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/KnownBits.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/ValueMapper.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <iterator>
#include <map>
#include <optional>
#include <utility>
using namespace llvm;
using namespace llvm::PatternMatch;
extern cl::opt<bool> UseNewDbgInfoFormat;
#define DEBUG_TYPE "local"
STATISTIC(NumRemoved, "Number of unreachable basic blocks removed");
STATISTIC(NumPHICSEs, "Number of PHI's that got CSE'd");
static cl::opt<bool> PHICSEDebugHash(
"phicse-debug-hash",
#ifdef EXPENSIVE_CHECKS
cl::init(true),
#else
cl::init(false),
#endif
cl::Hidden,
cl::desc("Perform extra assertion checking to verify that PHINodes's hash "
"function is well-behaved w.r.t. its isEqual predicate"));
static cl::opt<unsigned> PHICSENumPHISmallSize(
"phicse-num-phi-smallsize", cl::init(32), cl::Hidden,
cl::desc(
"When the basic block contains not more than this number of PHI nodes, "
"perform a (faster!) exhaustive search instead of set-driven one."));
// Max recursion depth for collectBitParts used when detecting bswap and
// bitreverse idioms.
static const unsigned BitPartRecursionMaxDepth = 48;
//===----------------------------------------------------------------------===//
// Local constant propagation.
//
/// ConstantFoldTerminator - If a terminator instruction is predicated on a
/// constant value, convert it into an unconditional branch to the constant
/// destination. This is a nontrivial operation because the successors of this
/// basic block must have their PHI nodes updated.
/// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch
/// conditions and indirectbr addresses this might make dead if
/// DeleteDeadConditions is true.
bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
const TargetLibraryInfo *TLI,
DomTreeUpdater *DTU) {
Instruction *T = BB->getTerminator();
IRBuilder<> Builder(T);
// Branch - See if we are conditional jumping on constant
if (auto *BI = dyn_cast<BranchInst>(T)) {
if (BI->isUnconditional()) return false; // Can't optimize uncond branch
BasicBlock *Dest1 = BI->getSuccessor(0);
BasicBlock *Dest2 = BI->getSuccessor(1);
if (Dest2 == Dest1) { // Conditional branch to same location?
// This branch matches something like this:
// br bool %cond, label %Dest, label %Dest
// and changes it into: br label %Dest
// Let the basic block know that we are letting go of one copy of it.
assert(BI->getParent() && "Terminator not inserted in block!");
Dest1->removePredecessor(BI->getParent());
// Replace the conditional branch with an unconditional one.
BranchInst *NewBI = Builder.CreateBr(Dest1);
// Transfer the metadata to the new branch instruction.
NewBI->copyMetadata(*BI, {LLVMContext::MD_loop, LLVMContext::MD_dbg,
LLVMContext::MD_annotation});
Value *Cond = BI->getCondition();
BI->eraseFromParent();
if (DeleteDeadConditions)
RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
return true;
}
if (auto *Cond = dyn_cast<ConstantInt>(BI->getCondition())) {
// Are we branching on constant?
// YES. Change to unconditional branch...
BasicBlock *Destination = Cond->getZExtValue() ? Dest1 : Dest2;
BasicBlock *OldDest = Cond->getZExtValue() ? Dest2 : Dest1;
// Let the basic block know that we are letting go of it. Based on this,
// it will adjust it's PHI nodes.
OldDest->removePredecessor(BB);
// Replace the conditional branch with an unconditional one.
BranchInst *NewBI = Builder.CreateBr(Destination);
// Transfer the metadata to the new branch instruction.
NewBI->copyMetadata(*BI, {LLVMContext::MD_loop, LLVMContext::MD_dbg,
LLVMContext::MD_annotation});
BI->eraseFromParent();
if (DTU)
DTU->applyUpdates({{DominatorTree::Delete, BB, OldDest}});
return true;
}
return false;
}
if (auto *SI = dyn_cast<SwitchInst>(T)) {
// If we are switching on a constant, we can convert the switch to an
// unconditional branch.
auto *CI = dyn_cast<ConstantInt>(SI->getCondition());
BasicBlock *DefaultDest = SI->getDefaultDest();
BasicBlock *TheOnlyDest = DefaultDest;
// If the default is unreachable, ignore it when searching for TheOnlyDest.
if (isa<UnreachableInst>(DefaultDest->getFirstNonPHIOrDbg()) &&
SI->getNumCases() > 0) {
TheOnlyDest = SI->case_begin()->getCaseSuccessor();
}
bool Changed = false;
// Figure out which case it goes to.
for (auto It = SI->case_begin(), End = SI->case_end(); It != End;) {
// Found case matching a constant operand?
if (It->getCaseValue() == CI) {
TheOnlyDest = It->getCaseSuccessor();
break;
}
// Check to see if this branch is going to the same place as the default
// dest. If so, eliminate it as an explicit compare.
if (It->getCaseSuccessor() == DefaultDest) {
MDNode *MD = getValidBranchWeightMDNode(*SI);
unsigned NCases = SI->getNumCases();
// Fold the case metadata into the default if there will be any branches
// left, unless the metadata doesn't match the switch.
if (NCases > 1 && MD) {
// Collect branch weights into a vector.
SmallVector<uint32_t, 8> Weights;
extractBranchWeights(MD, Weights);
// Merge weight of this case to the default weight.
unsigned Idx = It->getCaseIndex();
// TODO: Add overflow check.
Weights[0] += Weights[Idx + 1];
// Remove weight for this case.
std::swap(Weights[Idx + 1], Weights.back());
Weights.pop_back();
setBranchWeights(*SI, Weights);
}
// Remove this entry.
BasicBlock *ParentBB = SI->getParent();
DefaultDest->removePredecessor(ParentBB);
It = SI->removeCase(It);
End = SI->case_end();
// Removing this case may have made the condition constant. In that
// case, update CI and restart iteration through the cases.
if (auto *NewCI = dyn_cast<ConstantInt>(SI->getCondition())) {
CI = NewCI;
It = SI->case_begin();
}
Changed = true;
continue;
}
// Otherwise, check to see if the switch only branches to one destination.
// We do this by reseting "TheOnlyDest" to null when we find two non-equal
// destinations.
if (It->getCaseSuccessor() != TheOnlyDest)
TheOnlyDest = nullptr;
// Increment this iterator as we haven't removed the case.
++It;
}
if (CI && !TheOnlyDest) {
// Branching on a constant, but not any of the cases, go to the default
// successor.
TheOnlyDest = SI->getDefaultDest();
}
// If we found a single destination that we can fold the switch into, do so
// now.
if (TheOnlyDest) {
// Insert the new branch.
Builder.CreateBr(TheOnlyDest);
BasicBlock *BB = SI->getParent();
SmallSet<BasicBlock *, 8> RemovedSuccessors;
// Remove entries from PHI nodes which we no longer branch to...
BasicBlock *SuccToKeep = TheOnlyDest;
for (BasicBlock *Succ : successors(SI)) {
if (DTU && Succ != TheOnlyDest)
RemovedSuccessors.insert(Succ);
// Found case matching a constant operand?
if (Succ == SuccToKeep) {
SuccToKeep = nullptr; // Don't modify the first branch to TheOnlyDest
} else {
Succ->removePredecessor(BB);
}
}
// Delete the old switch.
Value *Cond = SI->getCondition();
SI->eraseFromParent();
if (DeleteDeadConditions)
RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
if (DTU) {
std::vector<DominatorTree::UpdateType> Updates;
Updates.reserve(RemovedSuccessors.size());
for (auto *RemovedSuccessor : RemovedSuccessors)
Updates.push_back({DominatorTree::Delete, BB, RemovedSuccessor});
DTU->applyUpdates(Updates);
}
return true;
}
if (SI->getNumCases() == 1) {
// Otherwise, we can fold this switch into a conditional branch
// instruction if it has only one non-default destination.
auto FirstCase = *SI->case_begin();
Value *Cond = Builder.CreateICmpEQ(SI->getCondition(),
FirstCase.getCaseValue(), "cond");
// Insert the new branch.
BranchInst *NewBr = Builder.CreateCondBr(Cond,
FirstCase.getCaseSuccessor(),
SI->getDefaultDest());
SmallVector<uint32_t> Weights;
if (extractBranchWeights(*SI, Weights) && Weights.size() == 2) {
uint32_t DefWeight = Weights[0];
uint32_t CaseWeight = Weights[1];
// The TrueWeight should be the weight for the single case of SI.
NewBr->setMetadata(LLVMContext::MD_prof,
MDBuilder(BB->getContext())
.createBranchWeights(CaseWeight, DefWeight));
}
// Update make.implicit metadata to the newly-created conditional branch.
MDNode *MakeImplicitMD = SI->getMetadata(LLVMContext::MD_make_implicit);
if (MakeImplicitMD)
NewBr->setMetadata(LLVMContext::MD_make_implicit, MakeImplicitMD);
// Delete the old switch.
SI->eraseFromParent();
return true;
}
return Changed;
}
if (auto *IBI = dyn_cast<IndirectBrInst>(T)) {
// indirectbr blockaddress(@F, @BB) -> br label @BB
if (auto *BA =
dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) {
BasicBlock *TheOnlyDest = BA->getBasicBlock();
SmallSet<BasicBlock *, 8> RemovedSuccessors;
// Insert the new branch.
Builder.CreateBr(TheOnlyDest);
BasicBlock *SuccToKeep = TheOnlyDest;
for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
BasicBlock *DestBB = IBI->getDestination(i);
if (DTU && DestBB != TheOnlyDest)
RemovedSuccessors.insert(DestBB);
if (IBI->getDestination(i) == SuccToKeep) {
SuccToKeep = nullptr;
} else {
DestBB->removePredecessor(BB);
}
}
Value *Address = IBI->getAddress();
IBI->eraseFromParent();
if (DeleteDeadConditions)
// Delete pointer cast instructions.
RecursivelyDeleteTriviallyDeadInstructions(Address, TLI);
// Also zap the blockaddress constant if there are no users remaining,
// otherwise the destination is still marked as having its address taken.
if (BA->use_empty())
BA->destroyConstant();
// If we didn't find our destination in the IBI successor list, then we
// have undefined behavior. Replace the unconditional branch with an
// 'unreachable' instruction.
if (SuccToKeep) {
BB->getTerminator()->eraseFromParent();
new UnreachableInst(BB->getContext(), BB);
}
if (DTU) {
std::vector<DominatorTree::UpdateType> Updates;
Updates.reserve(RemovedSuccessors.size());
for (auto *RemovedSuccessor : RemovedSuccessors)
Updates.push_back({DominatorTree::Delete, BB, RemovedSuccessor});
DTU->applyUpdates(Updates);
}
return true;
}
}
return false;
}
//===----------------------------------------------------------------------===//
// Local dead code elimination.
//
/// isInstructionTriviallyDead - Return true if the result produced by the
/// instruction is not used, and the instruction has no side effects.
///
bool llvm::isInstructionTriviallyDead(Instruction *I,
const TargetLibraryInfo *TLI) {
if (!I->use_empty())
return false;
return wouldInstructionBeTriviallyDead(I, TLI);
}
bool llvm::wouldInstructionBeTriviallyDeadOnUnusedPaths(
Instruction *I, const TargetLibraryInfo *TLI) {
// Instructions that are "markers" and have implied meaning on code around
// them (without explicit uses), are not dead on unused paths.
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
if (II->getIntrinsicID() == Intrinsic::stacksave ||
II->getIntrinsicID() == Intrinsic::launder_invariant_group ||
II->isLifetimeStartOrEnd())
return false;
return wouldInstructionBeTriviallyDead(I, TLI);
}
bool llvm::wouldInstructionBeTriviallyDead(const Instruction *I,
const TargetLibraryInfo *TLI) {
if (I->isTerminator())
return false;
// We don't want the landingpad-like instructions removed by anything this
// general.
if (I->isEHPad())
return false;
// We don't want debug info removed by anything this general.
if (isa<DbgVariableIntrinsic>(I))
return false;
if (const DbgLabelInst *DLI = dyn_cast<DbgLabelInst>(I)) {
if (DLI->getLabel())
return false;
return true;
}
if (auto *CB = dyn_cast<CallBase>(I))
if (isRemovableAlloc(CB, TLI))
return true;
if (!I->willReturn()) {
auto *II = dyn_cast<IntrinsicInst>(I);
if (!II)
return false;
switch (II->getIntrinsicID()) {
case Intrinsic::experimental_guard: {
// Guards on true are operationally no-ops. In the future we can
// consider more sophisticated tradeoffs for guards considering potential
// for check widening, but for now we keep things simple.
auto *Cond = dyn_cast<ConstantInt>(II->getArgOperand(0));
return Cond && Cond->isOne();
}
// TODO: These intrinsics are not safe to remove, because this may remove
// a well-defined trap.
case Intrinsic::wasm_trunc_signed:
case Intrinsic::wasm_trunc_unsigned:
case Intrinsic::ptrauth_auth:
case Intrinsic::ptrauth_resign:
return true;
default:
return false;
}
}
if (!I->mayHaveSideEffects())
return true;
// Special case intrinsics that "may have side effects" but can be deleted
// when dead.
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
// Safe to delete llvm.stacksave and launder.invariant.group if dead.
if (II->getIntrinsicID() == Intrinsic::stacksave ||
II->getIntrinsicID() == Intrinsic::launder_invariant_group)
return true;
// Intrinsics declare sideeffects to prevent them from moving, but they are
// nops without users.
if (II->getIntrinsicID() == Intrinsic::allow_runtime_check ||
II->getIntrinsicID() == Intrinsic::allow_ubsan_check)
return true;
if (II->isLifetimeStartOrEnd()) {
auto *Arg = II->getArgOperand(1);
// Lifetime intrinsics are dead when their right-hand is undef.
if (isa<UndefValue>(Arg))
return true;
// If the right-hand is an alloc, global, or argument and the only uses
// are lifetime intrinsics then the intrinsics are dead.
if (isa<AllocaInst>(Arg) || isa<GlobalValue>(Arg) || isa<Argument>(Arg))
return llvm::all_of(Arg->uses(), [](Use &Use) {
if (IntrinsicInst *IntrinsicUse =
dyn_cast<IntrinsicInst>(Use.getUser()))
return IntrinsicUse->isLifetimeStartOrEnd();
return false;
});
return false;
}
// Assumptions are dead if their condition is trivially true.
if (II->getIntrinsicID() == Intrinsic::assume &&
isAssumeWithEmptyBundle(cast<AssumeInst>(*II))) {
if (ConstantInt *Cond = dyn_cast<ConstantInt>(II->getArgOperand(0)))
return !Cond->isZero();
return false;
}
if (auto *FPI = dyn_cast<ConstrainedFPIntrinsic>(I)) {
std::optional<fp::ExceptionBehavior> ExBehavior =
FPI->getExceptionBehavior();
return *ExBehavior != fp::ebStrict;
}
}
if (auto *Call = dyn_cast<CallBase>(I)) {
if (Value *FreedOp = getFreedOperand(Call, TLI))
if (Constant *C = dyn_cast<Constant>(FreedOp))
return C->isNullValue() || isa<UndefValue>(C);
if (isMathLibCallNoop(Call, TLI))
return true;
}
// Non-volatile atomic loads from constants can be removed.
if (auto *LI = dyn_cast<LoadInst>(I))
if (auto *GV = dyn_cast<GlobalVariable>(
LI->getPointerOperand()->stripPointerCasts()))
if (!LI->isVolatile() && GV->isConstant())
return true;
return false;
}
/// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
/// trivially dead instruction, delete it. If that makes any of its operands
/// trivially dead, delete them too, recursively. Return true if any
/// instructions were deleted.
bool llvm::RecursivelyDeleteTriviallyDeadInstructions(
Value *V, const TargetLibraryInfo *TLI, MemorySSAUpdater *MSSAU,
std::function<void(Value *)> AboutToDeleteCallback) {
Instruction *I = dyn_cast<Instruction>(V);
if (!I || !isInstructionTriviallyDead(I, TLI))
return false;
SmallVector<WeakTrackingVH, 16> DeadInsts;
DeadInsts.push_back(I);
RecursivelyDeleteTriviallyDeadInstructions(DeadInsts, TLI, MSSAU,
AboutToDeleteCallback);
return true;
}
bool llvm::RecursivelyDeleteTriviallyDeadInstructionsPermissive(
SmallVectorImpl<WeakTrackingVH> &DeadInsts, const TargetLibraryInfo *TLI,
MemorySSAUpdater *MSSAU,
std::function<void(Value *)> AboutToDeleteCallback) {
unsigned S = 0, E = DeadInsts.size(), Alive = 0;
for (; S != E; ++S) {
auto *I = dyn_cast_or_null<Instruction>(DeadInsts[S]);
if (!I || !isInstructionTriviallyDead(I)) {
DeadInsts[S] = nullptr;
++Alive;
}
}
if (Alive == E)
return false;
RecursivelyDeleteTriviallyDeadInstructions(DeadInsts, TLI, MSSAU,
AboutToDeleteCallback);
return true;
}
void llvm::RecursivelyDeleteTriviallyDeadInstructions(
SmallVectorImpl<WeakTrackingVH> &DeadInsts, const TargetLibraryInfo *TLI,
MemorySSAUpdater *MSSAU,
std::function<void(Value *)> AboutToDeleteCallback) {
// Process the dead instruction list until empty.
while (!DeadInsts.empty()) {
Value *V = DeadInsts.pop_back_val();
Instruction *I = cast_or_null<Instruction>(V);
if (!I)
continue;
assert(isInstructionTriviallyDead(I, TLI) &&
"Live instruction found in dead worklist!");
assert(I->use_empty() && "Instructions with uses are not dead.");
// Don't lose the debug info while deleting the instructions.
salvageDebugInfo(*I);
if (AboutToDeleteCallback)
AboutToDeleteCallback(I);
// Null out all of the instruction's operands to see if any operand becomes
// dead as we go.
for (Use &OpU : I->operands()) {
Value *OpV = OpU.get();
OpU.set(nullptr);
if (!OpV->use_empty())
continue;
// If the operand is an instruction that became dead as we nulled out the
// operand, and if it is 'trivially' dead, delete it in a future loop
// iteration.
if (Instruction *OpI = dyn_cast<Instruction>(OpV))
if (isInstructionTriviallyDead(OpI, TLI))
DeadInsts.push_back(OpI);
}
if (MSSAU)
MSSAU->removeMemoryAccess(I);
I->eraseFromParent();
}
}
bool llvm::replaceDbgUsesWithUndef(Instruction *I) {
SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
SmallVector<DbgVariableRecord *, 1> DPUsers;
findDbgUsers(DbgUsers, I, &DPUsers);
for (auto *DII : DbgUsers)
DII->setKillLocation();
for (auto *DVR : DPUsers)
DVR->setKillLocation();
return !DbgUsers.empty() || !DPUsers.empty();
}
/// areAllUsesEqual - Check whether the uses of a value are all the same.
/// This is similar to Instruction::hasOneUse() except this will also return
/// true when there are no uses or multiple uses that all refer to the same
/// value.
static bool areAllUsesEqual(Instruction *I) {
Value::user_iterator UI = I->user_begin();
Value::user_iterator UE = I->user_end();
if (UI == UE)
return true;
User *TheUse = *UI;
for (++UI; UI != UE; ++UI) {
if (*UI != TheUse)
return false;
}
return true;
}
/// RecursivelyDeleteDeadPHINode - If the specified value is an effectively
/// dead PHI node, due to being a def-use chain of single-use nodes that
/// either forms a cycle or is terminated by a trivially dead instruction,
/// delete it. If that makes any of its operands trivially dead, delete them
/// too, recursively. Return true if a change was made.
bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN,
const TargetLibraryInfo *TLI,
llvm::MemorySSAUpdater *MSSAU) {
SmallPtrSet<Instruction*, 4> Visited;
for (Instruction *I = PN; areAllUsesEqual(I) && !I->mayHaveSideEffects();
I = cast<Instruction>(*I->user_begin())) {
if (I->use_empty())
return RecursivelyDeleteTriviallyDeadInstructions(I, TLI, MSSAU);
// If we find an instruction more than once, we're on a cycle that
// won't prove fruitful.
if (!Visited.insert(I).second) {
// Break the cycle and delete the instruction and its operands.
I->replaceAllUsesWith(PoisonValue::get(I->getType()));
(void)RecursivelyDeleteTriviallyDeadInstructions(I, TLI, MSSAU);
return true;
}
}
return false;
}
static bool
simplifyAndDCEInstruction(Instruction *I,
SmallSetVector<Instruction *, 16> &WorkList,
const DataLayout &DL,
const TargetLibraryInfo *TLI) {
if (isInstructionTriviallyDead(I, TLI)) {
salvageDebugInfo(*I);
// Null out all of the instruction's operands to see if any operand becomes
// dead as we go.
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
Value *OpV = I->getOperand(i);
I->setOperand(i, nullptr);
if (!OpV->use_empty() || I == OpV)
continue;
// If the operand is an instruction that became dead as we nulled out the
// operand, and if it is 'trivially' dead, delete it in a future loop
// iteration.
if (Instruction *OpI = dyn_cast<Instruction>(OpV))
if (isInstructionTriviallyDead(OpI, TLI))
WorkList.insert(OpI);
}
I->eraseFromParent();
return true;
}
if (Value *SimpleV = simplifyInstruction(I, DL)) {
// Add the users to the worklist. CAREFUL: an instruction can use itself,
// in the case of a phi node.
for (User *U : I->users()) {
if (U != I) {
WorkList.insert(cast<Instruction>(U));
}
}
// Replace the instruction with its simplified value.
bool Changed = false;
if (!I->use_empty()) {
I->replaceAllUsesWith(SimpleV);
Changed = true;
}
if (isInstructionTriviallyDead(I, TLI)) {
I->eraseFromParent();
Changed = true;
}
return Changed;
}
return false;
}
/// SimplifyInstructionsInBlock - Scan the specified basic block and try to
/// simplify any instructions in it and recursively delete dead instructions.
///
/// This returns true if it changed the code, note that it can delete
/// instructions in other blocks as well in this block.
bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB,
const TargetLibraryInfo *TLI) {
bool MadeChange = false;
const DataLayout &DL = BB->getModule()->getDataLayout();
#ifndef NDEBUG
// In debug builds, ensure that the terminator of the block is never replaced
// or deleted by these simplifications. The idea of simplification is that it
// cannot introduce new instructions, and there is no way to replace the
// terminator of a block without introducing a new instruction.
AssertingVH<Instruction> TerminatorVH(&BB->back());
#endif
SmallSetVector<Instruction *, 16> WorkList;
// Iterate over the original function, only adding insts to the worklist
// if they actually need to be revisited. This avoids having to pre-init
// the worklist with the entire function's worth of instructions.
for (BasicBlock::iterator BI = BB->begin(), E = std::prev(BB->end());
BI != E;) {
assert(!BI->isTerminator());
Instruction *I = &*BI;
++BI;
// We're visiting this instruction now, so make sure it's not in the
// worklist from an earlier visit.
if (!WorkList.count(I))
MadeChange |= simplifyAndDCEInstruction(I, WorkList, DL, TLI);
}
while (!WorkList.empty()) {
Instruction *I = WorkList.pop_back_val();
MadeChange |= simplifyAndDCEInstruction(I, WorkList, DL, TLI);
}
return MadeChange;
}
//===----------------------------------------------------------------------===//
// Control Flow Graph Restructuring.
//
void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB,
DomTreeUpdater *DTU) {
// If BB has single-entry PHI nodes, fold them.
while (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) {
Value *NewVal = PN->getIncomingValue(0);
// Replace self referencing PHI with poison, it must be dead.
if (NewVal == PN) NewVal = PoisonValue::get(PN->getType());
PN->replaceAllUsesWith(NewVal);
PN->eraseFromParent();
}
BasicBlock *PredBB = DestBB->getSinglePredecessor();
assert(PredBB && "Block doesn't have a single predecessor!");
bool ReplaceEntryBB = PredBB->isEntryBlock();
// DTU updates: Collect all the edges that enter
// PredBB. These dominator edges will be redirected to DestBB.
SmallVector<DominatorTree::UpdateType, 32> Updates;
if (DTU) {
// To avoid processing the same predecessor more than once.
SmallPtrSet<BasicBlock *, 2> SeenPreds;
Updates.reserve(Updates.size() + 2 * pred_size(PredBB) + 1);
for (BasicBlock *PredOfPredBB : predecessors(PredBB))
// This predecessor of PredBB may already have DestBB as a successor.
if (PredOfPredBB != PredBB)
if (SeenPreds.insert(PredOfPredBB).second)
Updates.push_back({DominatorTree::Insert, PredOfPredBB, DestBB});
SeenPreds.clear();
for (BasicBlock *PredOfPredBB : predecessors(PredBB))
if (SeenPreds.insert(PredOfPredBB).second)
Updates.push_back({DominatorTree::Delete, PredOfPredBB, PredBB});
Updates.push_back({DominatorTree::Delete, PredBB, DestBB});
}
// Zap anything that took the address of DestBB. Not doing this will give the
// address an invalid value.
if (DestBB->hasAddressTaken()) {
BlockAddress *BA = BlockAddress::get(DestBB);
Constant *Replacement =
ConstantInt::get(Type::getInt32Ty(BA->getContext()), 1);
BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement,
BA->getType()));
BA->destroyConstant();
}
// Anything that branched to PredBB now branches to DestBB.
PredBB->replaceAllUsesWith(DestBB);
// Splice all the instructions from PredBB to DestBB.
PredBB->getTerminator()->eraseFromParent();
DestBB->splice(DestBB->begin(), PredBB);
new UnreachableInst(PredBB->getContext(), PredBB);
// If the PredBB is the entry block of the function, move DestBB up to
// become the entry block after we erase PredBB.
if (ReplaceEntryBB)
DestBB->moveAfter(PredBB);
if (DTU) {
assert(PredBB->size() == 1 &&
isa<UnreachableInst>(PredBB->getTerminator()) &&
"The successor list of PredBB isn't empty before "
"applying corresponding DTU updates.");
DTU->applyUpdatesPermissive(Updates);
DTU->deleteBB(PredBB);
// Recalculation of DomTree is needed when updating a forward DomTree and
// the Entry BB is replaced.
if (ReplaceEntryBB && DTU->hasDomTree()) {
// The entry block was removed and there is no external interface for
// the dominator tree to be notified of this change. In this corner-case
// we recalculate the entire tree.
DTU->recalculate(*(DestBB->getParent()));
}
}
else {
PredBB->eraseFromParent(); // Nuke BB if DTU is nullptr.
}
}
/// Return true if we can choose one of these values to use in place of the
/// other. Note that we will always choose the non-undef value to keep.
static bool CanMergeValues(Value *First, Value *Second) {
return First == Second || isa<UndefValue>(First) || isa<UndefValue>(Second);
}
/// Return true if we can fold BB, an almost-empty BB ending in an unconditional
/// branch to Succ, into Succ.
///
/// Assumption: Succ is the single successor for BB.
static bool
CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ,
const SmallPtrSetImpl<BasicBlock *> &BBPreds) {
assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!");
LLVM_DEBUG(dbgs() << "Looking to fold " << BB->getName() << " into "
<< Succ->getName() << "\n");
// Shortcut, if there is only a single predecessor it must be BB and merging
// is always safe
if (Succ->getSinglePredecessor())
return true;
// Look at all the phi nodes in Succ, to see if they present a conflict when
// merging these blocks
for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
PHINode *PN = cast<PHINode>(I);
// If the incoming value from BB is again a PHINode in
// BB which has the same incoming value for *PI as PN does, we can
// merge the phi nodes and then the blocks can still be merged
PHINode *BBPN = dyn_cast<PHINode>(PN->getIncomingValueForBlock(BB));
if (BBPN && BBPN->getParent() == BB) {
for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
BasicBlock *IBB = PN->getIncomingBlock(PI);
if (BBPreds.count(IBB) &&
!CanMergeValues(BBPN->getIncomingValueForBlock(IBB),
PN->getIncomingValue(PI))) {
LLVM_DEBUG(dbgs()
<< "Can't fold, phi node " << PN->getName() << " in "
<< Succ->getName() << " is conflicting with "
<< BBPN->getName() << " with regard to common predecessor "
<< IBB->getName() << "\n");
return false;
}
}
} else {
Value* Val = PN->getIncomingValueForBlock(BB);
for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
// See if the incoming value for the common predecessor is equal to the
// one for BB, in which case this phi node will not prevent the merging
// of the block.
BasicBlock *IBB = PN->getIncomingBlock(PI);
if (BBPreds.count(IBB) &&
!CanMergeValues(Val, PN->getIncomingValue(PI))) {
LLVM_DEBUG(dbgs() << "Can't fold, phi node " << PN->getName()
<< " in " << Succ->getName()
<< " is conflicting with regard to common "
<< "predecessor " << IBB->getName() << "\n");
return false;
}
}
}
}
return true;
}
using PredBlockVector = SmallVector<BasicBlock *, 16>;
using IncomingValueMap = DenseMap<BasicBlock *, Value *>;
/// Determines the value to use as the phi node input for a block.
///
/// Select between \p OldVal any value that we know flows from \p BB
/// to a particular phi on the basis of which one (if either) is not
/// undef. Update IncomingValues based on the selected value.
///
/// \param OldVal The value we are considering selecting.
/// \param BB The block that the value flows in from.
/// \param IncomingValues A map from block-to-value for other phi inputs
/// that we have examined.
///
/// \returns the selected value.
static Value *selectIncomingValueForBlock(Value *OldVal, BasicBlock *BB,
IncomingValueMap &IncomingValues) {
if (!isa<UndefValue>(OldVal)) {
assert((!IncomingValues.count(BB) ||
IncomingValues.find(BB)->second == OldVal) &&
"Expected OldVal to match incoming value from BB!");
IncomingValues.insert(std::make_pair(BB, OldVal));
return OldVal;
}
IncomingValueMap::const_iterator It = IncomingValues.find(BB);
if (It != IncomingValues.end()) return It->second;
return OldVal;
}
/// Create a map from block to value for the operands of a
/// given phi.
///
/// Create a map from block to value for each non-undef value flowing
/// into \p PN.
///
/// \param PN The phi we are collecting the map for.
/// \param IncomingValues [out] The map from block to value for this phi.
static void gatherIncomingValuesToPhi(PHINode *PN,
IncomingValueMap &IncomingValues) {
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
BasicBlock *BB = PN->getIncomingBlock(i);
Value *V = PN->getIncomingValue(i);
if (!isa<UndefValue>(V))
IncomingValues.insert(std::make_pair(BB, V));
}
}
/// Replace the incoming undef values to a phi with the values
/// from a block-to-value map.
///
/// \param PN The phi we are replacing the undefs in.
/// \param IncomingValues A map from block to value.
static void replaceUndefValuesInPhi(PHINode *PN,
const IncomingValueMap &IncomingValues) {
SmallVector<unsigned> TrueUndefOps;
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
Value *V = PN->getIncomingValue(i);
if (!isa<UndefValue>(V)) continue;
BasicBlock *BB = PN->getIncomingBlock(i);
IncomingValueMap::const_iterator It = IncomingValues.find(BB);
// Keep track of undef/poison incoming values. Those must match, so we fix
// them up below if needed.
// Note: this is conservatively correct, but we could try harder and group
// the undef values per incoming basic block.
if (It == IncomingValues.end()) {
TrueUndefOps.push_back(i);
continue;
}
// There is a defined value for this incoming block, so map this undef
// incoming value to the defined value.
PN->setIncomingValue(i, It->second);
}
// If there are both undef and poison values incoming, then convert those
// values to undef. It is invalid to have different values for the same
// incoming block.
unsigned PoisonCount = count_if(TrueUndefOps, [&](unsigned i) {
return isa<PoisonValue>(PN->getIncomingValue(i));
});
if (PoisonCount != 0 && PoisonCount != TrueUndefOps.size()) {
for (unsigned i : TrueUndefOps)
PN->setIncomingValue(i, UndefValue::get(PN->getType()));
}
}
// Only when they shares a single common predecessor, return true.
// Only handles cases when BB can't be merged while its predecessors can be
// redirected.
static bool
CanRedirectPredsOfEmptyBBToSucc(BasicBlock *BB, BasicBlock *Succ,
const SmallPtrSetImpl<BasicBlock *> &BBPreds,
const SmallPtrSetImpl<BasicBlock *> &SuccPreds,
BasicBlock *&CommonPred) {
// There must be phis in BB, otherwise BB will be merged into Succ directly
if (BB->phis().empty() || Succ->phis().empty())
return false;
// BB must have predecessors not shared that can be redirected to Succ
if (!BB->hasNPredecessorsOrMore(2))
return false;
// Get single common predecessors of both BB and Succ
for (BasicBlock *SuccPred : SuccPreds) {
if (BBPreds.count(SuccPred)) {
if (CommonPred)
return false;
CommonPred = SuccPred;
}
}
return true;
}
/// Replace a value flowing from a block to a phi with
/// potentially multiple instances of that value flowing from the
/// block's predecessors to the phi.
///
/// \param BB The block with the value flowing into the phi.
/// \param BBPreds The predecessors of BB.
/// \param PN The phi that we are updating.
/// \param CommonPred The common predecessor of BB and PN's BasicBlock
static void redirectValuesFromPredecessorsToPhi(BasicBlock *BB,
const PredBlockVector &BBPreds,
PHINode *PN,
BasicBlock *CommonPred) {
Value *OldVal = PN->removeIncomingValue(BB, false);
assert(OldVal && "No entry in PHI for Pred BB!");
IncomingValueMap IncomingValues;
// We are merging two blocks - BB, and the block containing PN - and
// as a result we need to redirect edges from the predecessors of BB
// to go to the block containing PN, and update PN
// accordingly. Since we allow merging blocks in the case where the
// predecessor and successor blocks both share some predecessors,
// and where some of those common predecessors might have undef
// values flowing into PN, we want to rewrite those values to be
// consistent with the non-undef values.
gatherIncomingValuesToPhi(PN, IncomingValues);
// If this incoming value is one of the PHI nodes in BB, the new entries
// in the PHI node are the entries from the old PHI.
if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) {
PHINode *OldValPN = cast<PHINode>(OldVal);
for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i) {
// Note that, since we are merging phi nodes and BB and Succ might
// have common predecessors, we could end up with a phi node with
// identical incoming branches. This will be cleaned up later (and
// will trigger asserts if we try to clean it up now, without also
// simplifying the corresponding conditional branch).
BasicBlock *PredBB = OldValPN->getIncomingBlock(i);
if (PredBB == CommonPred)
continue;
Value *PredVal = OldValPN->getIncomingValue(i);
Value *Selected =
selectIncomingValueForBlock(PredVal, PredBB, IncomingValues);
// And add a new incoming value for this predecessor for the
// newly retargeted branch.
PN->addIncoming(Selected, PredBB);
}
if (CommonPred)
PN->addIncoming(OldValPN->getIncomingValueForBlock(CommonPred), BB);
} else {
for (unsigned i = 0, e = BBPreds.size(); i != e; ++i) {
// Update existing incoming values in PN for this
// predecessor of BB.
BasicBlock *PredBB = BBPreds[i];
if (PredBB == CommonPred)
continue;
Value *Selected =
selectIncomingValueForBlock(OldVal, PredBB, IncomingValues);
// And add a new incoming value for this predecessor for the
// newly retargeted branch.
PN->addIncoming(Selected, PredBB);
}
if (CommonPred)
PN->addIncoming(OldVal, BB);
}
replaceUndefValuesInPhi(PN, IncomingValues);
}
bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB,
DomTreeUpdater *DTU) {
assert(BB != &BB->getParent()->getEntryBlock() &&
"TryToSimplifyUncondBranchFromEmptyBlock called on entry block!");
// We can't simplify infinite loops.
BasicBlock *Succ = cast<BranchInst>(BB->getTerminator())->getSuccessor(0);
if (BB == Succ)
return false;
SmallPtrSet<BasicBlock *, 16> BBPreds(pred_begin(BB), pred_end(BB));
SmallPtrSet<BasicBlock *, 16> SuccPreds(pred_begin(Succ), pred_end(Succ));
// The single common predecessor of BB and Succ when BB cannot be killed
BasicBlock *CommonPred = nullptr;
bool BBKillable = CanPropagatePredecessorsForPHIs(BB, Succ, BBPreds);
// Even if we can not fold bB into Succ, we may be able to redirect the
// predecessors of BB to Succ.
bool BBPhisMergeable =
BBKillable ||
CanRedirectPredsOfEmptyBBToSucc(BB, Succ, BBPreds, SuccPreds, CommonPred);
if (!BBKillable && !BBPhisMergeable)
return false;
// Check to see if merging these blocks/phis would cause conflicts for any of
// the phi nodes in BB or Succ. If not, we can safely merge.
// Check for cases where Succ has multiple predecessors and a PHI node in BB
// has uses which will not disappear when the PHI nodes are merged. It is
// possible to handle such cases, but difficult: it requires checking whether
// BB dominates Succ, which is non-trivial to calculate in the case where
// Succ has multiple predecessors. Also, it requires checking whether
// constructing the necessary self-referential PHI node doesn't introduce any
// conflicts; this isn't too difficult, but the previous code for doing this
// was incorrect.
//
// Note that if this check finds a live use, BB dominates Succ, so BB is
// something like a loop pre-header (or rarely, a part of an irreducible CFG);
// folding the branch isn't profitable in that case anyway.
if (!Succ->getSinglePredecessor()) {
BasicBlock::iterator BBI = BB->begin();
while (isa<PHINode>(*BBI)) {
for (Use &U : BBI->uses()) {
if (PHINode* PN = dyn_cast<PHINode>(U.getUser())) {
if (PN->getIncomingBlock(U) != BB)
return false;
} else {
return false;
}
}
++BBI;
}
}
if (BBPhisMergeable && CommonPred)
LLVM_DEBUG(dbgs() << "Found Common Predecessor between: " << BB->getName()
<< " and " << Succ->getName() << " : "
<< CommonPred->getName() << "\n");
// 'BB' and 'BB->Pred' are loop latches, bail out to presrve inner loop
// metadata.
//
// FIXME: This is a stop-gap solution to preserve inner-loop metadata given
// current status (that loop metadata is implemented as metadata attached to
// the branch instruction in the loop latch block). To quote from review
// comments, "the current representation of loop metadata (using a loop latch
// terminator attachment) is known to be fundamentally broken. Loop latches
// are not uniquely associated with loops (both in that a latch can be part of
// multiple loops and a loop may have multiple latches). Loop headers are. The
// solution to this problem is also known: Add support for basic block
// metadata, and attach loop metadata to the loop header."
//
// Why bail out:
// In this case, we expect 'BB' is the latch for outer-loop and 'BB->Pred' is
// the latch for inner-loop (see reason below), so bail out to prerserve
// inner-loop metadata rather than eliminating 'BB' and attaching its metadata
// to this inner-loop.
// - The reason we believe 'BB' and 'BB->Pred' have different inner-most
// loops: assuming 'BB' and 'BB->Pred' are from the same inner-most loop L,
// then 'BB' is the header and latch of 'L' and thereby 'L' must consist of
// one self-looping basic block, which is contradictory with the assumption.
//
// To illustrate how inner-loop metadata is dropped:
//
// CFG Before
//
// BB is while.cond.exit, attached with loop metdata md2.
// BB->Pred is for.body, attached with loop metadata md1.
//
// entry
// |
// v
// ---> while.cond -------------> while.end
// | |
// | v
// | while.body
// | |
// | v
// | for.body <---- (md1)
// | | |______|
// | v
// | while.cond.exit (md2)
// | |
// |_______|
//
// CFG After
//
// while.cond1 is the merge of while.cond.exit and while.cond above.
// for.body is attached with md2, and md1 is dropped.
// If LoopSimplify runs later (as a part of loop pass), it could create
// dedicated exits for inner-loop (essentially adding `while.cond.exit`
// back), but won't it won't see 'md1' nor restore it for the inner-loop.
//
// entry
// |
// v
// ---> while.cond1 -------------> while.end
// | |
// | v
// | while.body
// | |
// | v
// | for.body <---- (md2)
// |_______| |______|
if (Instruction *TI = BB->getTerminator())
if (TI->hasMetadata(LLVMContext::MD_loop))
for (BasicBlock *Pred : predecessors(BB))
if (Instruction *PredTI = Pred->getTerminator())
if (PredTI->hasMetadata(LLVMContext::MD_loop))
return false;
if (BBKillable)
LLVM_DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB);
else if (BBPhisMergeable)
LLVM_DEBUG(dbgs() << "Merge Phis in Trivial BB: \n" << *BB);
SmallVector<DominatorTree::UpdateType, 32> Updates;
if (DTU) {
// To avoid processing the same predecessor more than once.
SmallPtrSet<BasicBlock *, 8> SeenPreds;
// All predecessors of BB (except the common predecessor) will be moved to
// Succ.
Updates.reserve(Updates.size() + 2 * pred_size(BB) + 1);
for (auto *PredOfBB : predecessors(BB)) {
// Do not modify those common predecessors of BB and Succ
if (!SuccPreds.contains(PredOfBB))
if (SeenPreds.insert(PredOfBB).second)
Updates.push_back({DominatorTree::Insert, PredOfBB, Succ});
}
SeenPreds.clear();
for (auto *PredOfBB : predecessors(BB))
// When BB cannot be killed, do not remove the edge between BB and
// CommonPred.
if (SeenPreds.insert(PredOfBB).second && PredOfBB != CommonPred)
Updates.push_back({DominatorTree::Delete, PredOfBB, BB});
if (BBKillable)
Updates.push_back({DominatorTree::Delete, BB, Succ});
}
if (isa<PHINode>(Succ->begin())) {
// If there is more than one pred of succ, and there are PHI nodes in
// the successor, then we need to add incoming edges for the PHI nodes
//
const PredBlockVector BBPreds(predecessors(BB));
// Loop over all of the PHI nodes in the successor of BB.
for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
PHINode *PN = cast<PHINode>(I);
redirectValuesFromPredecessorsToPhi(BB, BBPreds, PN, CommonPred);
}
}
if (Succ->getSinglePredecessor()) {
// BB is the only predecessor of Succ, so Succ will end up with exactly
// the same predecessors BB had.
// Copy over any phi, debug or lifetime instruction.
BB->getTerminator()->eraseFromParent();
Succ->splice(Succ->getFirstNonPHIIt(), BB);
} else {
while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
// We explicitly check for such uses for merging phis.
assert(PN->use_empty() && "There shouldn't be any uses here!");
PN->eraseFromParent();
}
}
// If the unconditional branch we replaced contains llvm.loop metadata, we
// add the metadata to the branch instructions in the predecessors.
if (Instruction *TI = BB->getTerminator())
if (MDNode *LoopMD = TI->getMetadata(LLVMContext::MD_loop))
for (BasicBlock *Pred : predecessors(BB))
Pred->getTerminator()->setMetadata(LLVMContext::MD_loop, LoopMD);
if (BBKillable) {
// Everything that jumped to BB now goes to Succ.
BB->replaceAllUsesWith(Succ);
if (!Succ->hasName())
Succ->takeName(BB);
// Clear the successor list of BB to match updates applying to DTU later.
if (BB->getTerminator())
BB->back().eraseFromParent();
new UnreachableInst(BB->getContext(), BB);
assert(succ_empty(BB) && "The successor list of BB isn't empty before "
"applying corresponding DTU updates.");
} else if (BBPhisMergeable) {
// Everything except CommonPred that jumped to BB now goes to Succ.
BB->replaceUsesWithIf(Succ, [BBPreds, CommonPred](Use &U) -> bool {
if (Instruction *UseInst = dyn_cast<Instruction>(U.getUser()))
return UseInst->getParent() != CommonPred &&
BBPreds.contains(UseInst->getParent());
return false;
});
}
if (DTU)
DTU->applyUpdates(Updates);
if (BBKillable)
DeleteDeadBlock(BB, DTU);
return true;
}
static bool
EliminateDuplicatePHINodesNaiveImpl(BasicBlock *BB,
SmallPtrSetImpl<PHINode *> &ToRemove) {
// This implementation doesn't currently consider undef operands
// specially. Theoretically, two phis which are identical except for
// one having an undef where the other doesn't could be collapsed.
bool Changed = false;
// Examine each PHI.
// Note that increment of I must *NOT* be in the iteration_expression, since
// we don't want to immediately advance when we restart from the beginning.
for (auto I = BB->begin(); PHINode *PN = dyn_cast<PHINode>(I);) {
++I;
// Is there an identical PHI node in this basic block?
// Note that we only look in the upper square's triangle,
// we already checked that the lower triangle PHI's aren't identical.
for (auto J = I; PHINode *DuplicatePN = dyn_cast<PHINode>(J); ++J) {
if (ToRemove.contains(DuplicatePN))
continue;
if (!DuplicatePN->isIdenticalToWhenDefined(PN))
continue;
// A duplicate. Replace this PHI with the base PHI.
++NumPHICSEs;
DuplicatePN->replaceAllUsesWith(PN);
ToRemove.insert(DuplicatePN);
Changed = true;
// The RAUW can change PHIs that we already visited.
I = BB->begin();
break; // Start over from the beginning.
}
}
return Changed;
}
static bool
EliminateDuplicatePHINodesSetBasedImpl(BasicBlock *BB,
SmallPtrSetImpl<PHINode *> &ToRemove) {
// This implementation doesn't currently consider undef operands
// specially. Theoretically, two phis which are identical except for
// one having an undef where the other doesn't could be collapsed.
struct PHIDenseMapInfo {
static PHINode *getEmptyKey() {
return DenseMapInfo<PHINode *>::getEmptyKey();
}
static PHINode *getTombstoneKey() {
return DenseMapInfo<PHINode *>::getTombstoneKey();
}
static bool isSentinel(PHINode *PN) {
return PN == getEmptyKey() || PN == getTombstoneKey();
}
// WARNING: this logic must be kept in sync with
// Instruction::isIdenticalToWhenDefined()!
static unsigned getHashValueImpl(PHINode *PN) {
// Compute a hash value on the operands. Instcombine will likely have
// sorted them, which helps expose duplicates, but we have to check all
// the operands to be safe in case instcombine hasn't run.
return static_cast<unsigned>(hash_combine(
hash_combine_range(PN->value_op_begin(), PN->value_op_end()),
hash_combine_range(PN->block_begin(), PN->block_end())));
}
static unsigned getHashValue(PHINode *PN) {
#ifndef NDEBUG
// If -phicse-debug-hash was specified, return a constant -- this
// will force all hashing to collide, so we'll exhaustively search
// the table for a match, and the assertion in isEqual will fire if
// there's a bug causing equal keys to hash differently.
if (PHICSEDebugHash)
return 0;
#endif
return getHashValueImpl(PN);
}
static bool isEqualImpl(PHINode *LHS, PHINode *RHS) {
if (isSentinel(LHS) || isSentinel(RHS))
return LHS == RHS;
return LHS->isIdenticalTo(RHS);
}
static bool isEqual(PHINode *LHS, PHINode *RHS) {
// These comparisons are nontrivial, so assert that equality implies
// hash equality (DenseMap demands this as an invariant).
bool Result = isEqualImpl(LHS, RHS);
assert(!Result || (isSentinel(LHS) && LHS == RHS) ||
getHashValueImpl(LHS) == getHashValueImpl(RHS));
return Result;
}
};
// Set of unique PHINodes.
DenseSet<PHINode *, PHIDenseMapInfo> PHISet;
PHISet.reserve(4 * PHICSENumPHISmallSize);
// Examine each PHI.
bool Changed = false;
for (auto I = BB->begin(); PHINode *PN = dyn_cast<PHINode>(I++);) {
if (ToRemove.contains(PN))
continue;
auto Inserted = PHISet.insert(PN);
if (!Inserted.second) {
// A duplicate. Replace this PHI with its duplicate.
++NumPHICSEs;
PN->replaceAllUsesWith(*Inserted.first);
ToRemove.insert(PN);
Changed = true;
// The RAUW can change PHIs that we already visited. Start over from the
// beginning.
PHISet.clear();
I = BB->begin();
}
}
return Changed;
}
bool llvm::EliminateDuplicatePHINodes(BasicBlock *BB,
SmallPtrSetImpl<PHINode *> &ToRemove) {
if (
#ifndef NDEBUG
!PHICSEDebugHash &&
#endif
hasNItemsOrLess(BB->phis(), PHICSENumPHISmallSize))
return EliminateDuplicatePHINodesNaiveImpl(BB, ToRemove);
return EliminateDuplicatePHINodesSetBasedImpl(BB, ToRemove);
}
bool llvm::EliminateDuplicatePHINodes(BasicBlock *BB) {
SmallPtrSet<PHINode *, 8> ToRemove;
bool Changed = EliminateDuplicatePHINodes(BB, ToRemove);
for (PHINode *PN : ToRemove)
PN->eraseFromParent();
return Changed;
}
Align llvm::tryEnforceAlignment(Value *V, Align PrefAlign,
const DataLayout &DL) {
V = V->stripPointerCasts();
if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
// TODO: Ideally, this function would not be called if PrefAlign is smaller
// than the current alignment, as the known bits calculation should have
// already taken it into account. However, this is not always the case,
// as computeKnownBits() has a depth limit, while stripPointerCasts()
// doesn't.
Align CurrentAlign = AI->getAlign();
if (PrefAlign <= CurrentAlign)
return CurrentAlign;
// If the preferred alignment is greater than the natural stack alignment
// then don't round up. This avoids dynamic stack realignment.
if (DL.exceedsNaturalStackAlignment(PrefAlign))
return CurrentAlign;
AI->setAlignment(PrefAlign);
return PrefAlign;
}
if (auto *GO = dyn_cast<GlobalObject>(V)) {
// TODO: as above, this shouldn't be necessary.
Align CurrentAlign = GO->getPointerAlignment(DL);
if (PrefAlign <= CurrentAlign)
return CurrentAlign;
// If there is a large requested alignment and we can, bump up the alignment
// of the global. If the memory we set aside for the global may not be the
// memory used by the final program then it is impossible for us to reliably
// enforce the preferred alignment.
if (!GO->canIncreaseAlignment())
return CurrentAlign;
if (GO->isThreadLocal()) {
unsigned MaxTLSAlign = GO->getParent()->getMaxTLSAlignment() / CHAR_BIT;
if (MaxTLSAlign && PrefAlign > Align(MaxTLSAlign))
PrefAlign = Align(MaxTLSAlign);
}
GO->setAlignment(PrefAlign);
return PrefAlign;
}
return Align(1);
}
Align llvm::getOrEnforceKnownAlignment(Value *V, MaybeAlign PrefAlign,
const DataLayout &DL,
const Instruction *CxtI,
AssumptionCache *AC,
const DominatorTree *DT) {
assert(V->getType()->isPointerTy() &&
"getOrEnforceKnownAlignment expects a pointer!");
KnownBits Known = computeKnownBits(V, DL, 0, AC, CxtI, DT);
unsigned TrailZ = Known.countMinTrailingZeros();
// Avoid trouble with ridiculously large TrailZ values, such as
// those computed from a null pointer.
// LLVM doesn't support alignments larger than (1 << MaxAlignmentExponent).
TrailZ = std::min(TrailZ, +Value::MaxAlignmentExponent);
Align Alignment = Align(1ull << std::min(Known.getBitWidth() - 1, TrailZ));
if (PrefAlign && *PrefAlign > Alignment)
Alignment = std::max(Alignment, tryEnforceAlignment(V, *PrefAlign, DL));
// We don't need to make any adjustment.
return Alignment;
}
///===---------------------------------------------------------------------===//
/// Dbg Intrinsic utilities
///
/// See if there is a dbg.value intrinsic for DIVar for the PHI node.
static bool PhiHasDebugValue(DILocalVariable *DIVar,
DIExpression *DIExpr,
PHINode *APN) {
// Since we can't guarantee that the original dbg.declare intrinsic
// is removed by LowerDbgDeclare(), we need to make sure that we are
// not inserting the same dbg.value intrinsic over and over.
SmallVector<DbgValueInst *, 1> DbgValues;
SmallVector<DbgVariableRecord *, 1> DbgVariableRecords;
findDbgValues(DbgValues, APN, &DbgVariableRecords);
for (auto *DVI : DbgValues) {
assert(is_contained(DVI->getValues(), APN));
if ((DVI->getVariable() == DIVar) && (DVI->getExpression() == DIExpr))
return true;
}
for (auto *DVR : DbgVariableRecords) {
assert(is_contained(DVR->location_ops(), APN));
if ((DVR->getVariable() == DIVar) && (DVR->getExpression() == DIExpr))
return true;
}
return false;
}
/// Check if the alloc size of \p ValTy is large enough to cover the variable
/// (or fragment of the variable) described by \p DII.
///
/// This is primarily intended as a helper for the different
/// ConvertDebugDeclareToDebugValue functions. The dbg.declare that is converted
/// describes an alloca'd variable, so we need to use the alloc size of the
/// value when doing the comparison. E.g. an i1 value will be identified as
/// covering an n-bit fragment, if the store size of i1 is at least n bits.
static bool valueCoversEntireFragment(Type *ValTy, DbgVariableIntrinsic *DII) {
const DataLayout &DL = DII->getModule()->getDataLayout();
TypeSize ValueSize = DL.getTypeAllocSizeInBits(ValTy);
if (std::optional<uint64_t> FragmentSize = DII->getFragmentSizeInBits())
return TypeSize::isKnownGE(ValueSize, TypeSize::getFixed(*FragmentSize));
// We can't always calculate the size of the DI variable (e.g. if it is a
// VLA). Try to use the size of the alloca that the dbg intrinsic describes
// intead.
if (DII->isAddressOfVariable()) {
// DII should have exactly 1 location when it is an address.
assert(DII->getNumVariableLocationOps() == 1 &&
"address of variable must have exactly 1 location operand.");
if (auto *AI =
dyn_cast_or_null<AllocaInst>(DII->getVariableLocationOp(0))) {
if (std::optional<TypeSize> FragmentSize =
AI->getAllocationSizeInBits(DL)) {
return TypeSize::isKnownGE(ValueSize, *FragmentSize);
}
}
}
// Could not determine size of variable. Conservatively return false.
return false;
}
// RemoveDIs: duplicate implementation of the above, using DbgVariableRecords,
// the replacement for dbg.values.
static bool valueCoversEntireFragment(Type *ValTy, DbgVariableRecord *DVR) {
const DataLayout &DL = DVR->getModule()->getDataLayout();
TypeSize ValueSize = DL.getTypeAllocSizeInBits(ValTy);
if (std::optional<uint64_t> FragmentSize = DVR->getFragmentSizeInBits())
return TypeSize::isKnownGE(ValueSize, TypeSize::getFixed(*FragmentSize));
// We can't always calculate the size of the DI variable (e.g. if it is a
// VLA). Try to use the size of the alloca that the dbg intrinsic describes
// intead.
if (DVR->isAddressOfVariable()) {
// DVR should have exactly 1 location when it is an address.
assert(DVR->getNumVariableLocationOps() == 1 &&
"address of variable must have exactly 1 location operand.");
if (auto *AI =
dyn_cast_or_null<AllocaInst>(DVR->getVariableLocationOp(0))) {
if (std::optional<TypeSize> FragmentSize = AI->getAllocationSizeInBits(DL)) {
return TypeSize::isKnownGE(ValueSize, *FragmentSize);
}
}
}
// Could not determine size of variable. Conservatively return false.
return false;
}
static void insertDbgValueOrDbgVariableRecord(DIBuilder &Builder, Value *DV,
DILocalVariable *DIVar,
DIExpression *DIExpr,
const DebugLoc &NewLoc,
BasicBlock::iterator Instr) {
if (!UseNewDbgInfoFormat) {
auto DbgVal = Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, NewLoc,
(Instruction *)nullptr);
DbgVal.get<Instruction *>()->insertBefore(Instr);
} else {
// RemoveDIs: if we're using the new debug-info format, allocate a
// DbgVariableRecord directly instead of a dbg.value intrinsic.
ValueAsMetadata *DVAM = ValueAsMetadata::get(DV);
DbgVariableRecord *DV =
new DbgVariableRecord(DVAM, DIVar, DIExpr, NewLoc.get());
Instr->getParent()->insertDbgRecordBefore(DV, Instr);
}
}
static void insertDbgValueOrDbgVariableRecordAfter(
DIBuilder &Builder, Value *DV, DILocalVariable *DIVar, DIExpression *DIExpr,
const DebugLoc &NewLoc, BasicBlock::iterator Instr) {
if (!UseNewDbgInfoFormat) {
auto DbgVal = Builder.insertDbgValueIntrinsic(DV, DIVar, DIExpr, NewLoc,
(Instruction *)nullptr);
DbgVal.get<Instruction *>()->insertAfter(&*Instr);
} else {
// RemoveDIs: if we're using the new debug-info format, allocate a
// DbgVariableRecord directly instead of a dbg.value intrinsic.
ValueAsMetadata *DVAM = ValueAsMetadata::get(DV);
DbgVariableRecord *DV =
new DbgVariableRecord(DVAM, DIVar, DIExpr, NewLoc.get());
Instr->getParent()->insertDbgRecordAfter(DV, &*Instr);
}
}
/// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value
/// that has an associated llvm.dbg.declare intrinsic.
void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII,
StoreInst *SI, DIBuilder &Builder) {
assert(DII->isAddressOfVariable() || isa<DbgAssignIntrinsic>(DII));
auto *DIVar = DII->getVariable();
assert(DIVar && "Missing variable");
auto *DIExpr = DII->getExpression();
Value *DV = SI->getValueOperand();
DebugLoc NewLoc = getDebugValueLoc(DII);
// If the alloca describes the variable itself, i.e. the expression in the
// dbg.declare doesn't start with a dereference, we can perform the
// conversion if the value covers the entire fragment of DII.
// If the alloca describes the *address* of DIVar, i.e. DIExpr is
// *just* a DW_OP_deref, we use DV as is for the dbg.value.
// We conservatively ignore other dereferences, because the following two are
// not equivalent:
// dbg.declare(alloca, ..., !Expr(deref, plus_uconstant, 2))
// dbg.value(DV, ..., !Expr(deref, plus_uconstant, 2))
// The former is adding 2 to the address of the variable, whereas the latter
// is adding 2 to the value of the variable. As such, we insist on just a
// deref expression.
bool CanConvert =
DIExpr->isDeref() || (!DIExpr->startsWithDeref() &&
valueCoversEntireFragment(DV->getType(), DII));
if (CanConvert) {
insertDbgValueOrDbgVariableRecord(Builder, DV, DIVar, DIExpr, NewLoc,
SI->getIterator());
return;
}
// FIXME: If storing to a part of the variable described by the dbg.declare,
// then we want to insert a dbg.value for the corresponding fragment.
LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: " << *DII
<< '\n');
// For now, when there is a store to parts of the variable (but we do not
// know which part) we insert an dbg.value intrinsic to indicate that we
// know nothing about the variable's content.
DV = UndefValue::get(DV->getType());
insertDbgValueOrDbgVariableRecord(Builder, DV, DIVar, DIExpr, NewLoc,
SI->getIterator());
}
/// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value
/// that has an associated llvm.dbg.declare intrinsic.
void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII,
LoadInst *LI, DIBuilder &Builder) {
auto *DIVar = DII->getVariable();
auto *DIExpr = DII->getExpression();
assert(DIVar && "Missing variable");
if (!valueCoversEntireFragment(LI->getType(), DII)) {
// FIXME: If only referring to a part of the variable described by the
// dbg.declare, then we want to insert a dbg.value for the corresponding
// fragment.
LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: "
<< *DII << '\n');
return;
}
DebugLoc NewLoc = getDebugValueLoc(DII);
// We are now tracking the loaded value instead of the address. In the
// future if multi-location support is added to the IR, it might be
// preferable to keep tracking both the loaded value and the original
// address in case the alloca can not be elided.
insertDbgValueOrDbgVariableRecordAfter(Builder, LI, DIVar, DIExpr, NewLoc,
LI->getIterator());
}
void llvm::ConvertDebugDeclareToDebugValue(DbgVariableRecord *DVR,
StoreInst *SI, DIBuilder &Builder) {
assert(DVR->isAddressOfVariable() || DVR->isDbgAssign());
auto *DIVar = DVR->getVariable();
assert(DIVar && "Missing variable");
auto *DIExpr = DVR->getExpression();
Value *DV = SI->getValueOperand();
DebugLoc NewLoc = getDebugValueLoc(DVR);
// If the alloca describes the variable itself, i.e. the expression in the
// dbg.declare doesn't start with a dereference, we can perform the
// conversion if the value covers the entire fragment of DII.
// If the alloca describes the *address* of DIVar, i.e. DIExpr is
// *just* a DW_OP_deref, we use DV as is for the dbg.value.
// We conservatively ignore other dereferences, because the following two are
// not equivalent:
// dbg.declare(alloca, ..., !Expr(deref, plus_uconstant, 2))
// dbg.value(DV, ..., !Expr(deref, plus_uconstant, 2))
// The former is adding 2 to the address of the variable, whereas the latter
// is adding 2 to the value of the variable. As such, we insist on just a
// deref expression.
bool CanConvert =
DIExpr->isDeref() || (!DIExpr->startsWithDeref() &&
valueCoversEntireFragment(DV->getType(), DVR));
if (CanConvert) {
insertDbgValueOrDbgVariableRecord(Builder, DV, DIVar, DIExpr, NewLoc,
SI->getIterator());
return;
}
// FIXME: If storing to a part of the variable described by the dbg.declare,
// then we want to insert a dbg.value for the corresponding fragment.
LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: " << *DVR
<< '\n');
assert(UseNewDbgInfoFormat);
// For now, when there is a store to parts of the variable (but we do not
// know which part) we insert an dbg.value intrinsic to indicate that we
// know nothing about the variable's content.
DV = UndefValue::get(DV->getType());
ValueAsMetadata *DVAM = ValueAsMetadata::get(DV);
DbgVariableRecord *NewDVR =
new DbgVariableRecord(DVAM, DIVar, DIExpr, NewLoc.get());
SI->getParent()->insertDbgRecordBefore(NewDVR, SI->getIterator());
}
/// Inserts a llvm.dbg.value intrinsic after a phi that has an associated
/// llvm.dbg.declare intrinsic.
void llvm::ConvertDebugDeclareToDebugValue(DbgVariableIntrinsic *DII,
PHINode *APN, DIBuilder &Builder) {
auto *DIVar = DII->getVariable();
auto *DIExpr = DII->getExpression();
assert(DIVar && "Missing variable");
if (PhiHasDebugValue(DIVar, DIExpr, APN))
return;
if (!valueCoversEntireFragment(APN->getType(), DII)) {
// FIXME: If only referring to a part of the variable described by the
// dbg.declare, then we want to insert a dbg.value for the corresponding
// fragment.
LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to dbg.value: "
<< *DII << '\n');
return;
}
BasicBlock *BB = APN->getParent();
auto InsertionPt = BB->getFirstInsertionPt();
DebugLoc NewLoc = getDebugValueLoc(DII);
// The block may be a catchswitch block, which does not have a valid
// insertion point.
// FIXME: Insert dbg.value markers in the successors when appropriate.
if (InsertionPt != BB->end()) {
insertDbgValueOrDbgVariableRecord(Builder, APN, DIVar, DIExpr, NewLoc,
InsertionPt);
}
}
void llvm::ConvertDebugDeclareToDebugValue(DbgVariableRecord *DVR, LoadInst *LI,
DIBuilder &Builder) {
auto *DIVar = DVR->getVariable();
auto *DIExpr = DVR->getExpression();
assert(DIVar && "Missing variable");
if (!valueCoversEntireFragment(LI->getType(), DVR)) {
// FIXME: If only referring to a part of the variable described by the
// dbg.declare, then we want to insert a DbgVariableRecord for the
// corresponding fragment.
LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to DbgVariableRecord: "
<< *DVR << '\n');
return;
}
DebugLoc NewLoc = getDebugValueLoc(DVR);
// We are now tracking the loaded value instead of the address. In the
// future if multi-location support is added to the IR, it might be
// preferable to keep tracking both the loaded value and the original
// address in case the alloca can not be elided.
assert(UseNewDbgInfoFormat);
// Create a DbgVariableRecord directly and insert.
ValueAsMetadata *LIVAM = ValueAsMetadata::get(LI);
DbgVariableRecord *DV =
new DbgVariableRecord(LIVAM, DIVar, DIExpr, NewLoc.get());
LI->getParent()->insertDbgRecordAfter(DV, LI);
}
/// Determine whether this alloca is either a VLA or an array.
static bool isArray(AllocaInst *AI) {
return AI->isArrayAllocation() ||
(AI->getAllocatedType() && AI->getAllocatedType()->isArrayTy());
}
/// Determine whether this alloca is a structure.
static bool isStructure(AllocaInst *AI) {
return AI->getAllocatedType() && AI->getAllocatedType()->isStructTy();
}
void llvm::ConvertDebugDeclareToDebugValue(DbgVariableRecord *DVR, PHINode *APN,
DIBuilder &Builder) {
auto *DIVar = DVR->getVariable();
auto *DIExpr = DVR->getExpression();
assert(DIVar && "Missing variable");
if (PhiHasDebugValue(DIVar, DIExpr, APN))
return;
if (!valueCoversEntireFragment(APN->getType(), DVR)) {
// FIXME: If only referring to a part of the variable described by the
// dbg.declare, then we want to insert a DbgVariableRecord for the
// corresponding fragment.
LLVM_DEBUG(dbgs() << "Failed to convert dbg.declare to DbgVariableRecord: "
<< *DVR << '\n');
return;
}
BasicBlock *BB = APN->getParent();
auto InsertionPt = BB->getFirstInsertionPt();
DebugLoc NewLoc = getDebugValueLoc(DVR);
// The block may be a catchswitch block, which does not have a valid
// insertion point.
// FIXME: Insert DbgVariableRecord markers in the successors when appropriate.
if (InsertionPt != BB->end()) {
insertDbgValueOrDbgVariableRecord(Builder, APN, DIVar, DIExpr, NewLoc,
InsertionPt);
}
}
/// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
/// of llvm.dbg.value intrinsics.
bool llvm::LowerDbgDeclare(Function &F) {
bool Changed = false;
DIBuilder DIB(*F.getParent(), /*AllowUnresolved*/ false);
SmallVector<DbgDeclareInst *, 4> Dbgs;
SmallVector<DbgVariableRecord *> DVRs;
for (auto &FI : F) {
for (Instruction &BI : FI) {
if (auto *DDI = dyn_cast<DbgDeclareInst>(&BI))
Dbgs.push_back(DDI);
for (DbgVariableRecord &DVR : filterDbgVars(BI.getDbgRecordRange())) {
if (DVR.getType() == DbgVariableRecord::LocationType::Declare)
DVRs.push_back(&DVR);
}
}
}
if (Dbgs.empty() && DVRs.empty())
return Changed;
auto LowerOne = [&](auto *DDI) {
AllocaInst *AI =
dyn_cast_or_null<AllocaInst>(DDI->getVariableLocationOp(0));
// If this is an alloca for a scalar variable, insert a dbg.value
// at each load and store to the alloca and erase the dbg.declare.
// The dbg.values allow tracking a variable even if it is not
// stored on the stack, while the dbg.declare can only describe
// the stack slot (and at a lexical-scope granularity). Later
// passes will attempt to elide the stack slot.
if (!AI || isArray(AI) || isStructure(AI))
return;
// A volatile load/store means that the alloca can't be elided anyway.
if (llvm::any_of(AI->users(), [](User *U) -> bool {
if (LoadInst *LI = dyn_cast<LoadInst>(U))
return LI->isVolatile();
if (StoreInst *SI = dyn_cast<StoreInst>(U))
return SI->isVolatile();
return false;
}))
return;
SmallVector<const Value *, 8> WorkList;
WorkList.push_back(AI);
while (!WorkList.empty()) {
const Value *V = WorkList.pop_back_val();
for (const auto &AIUse : V->uses()) {
User *U = AIUse.getUser();
if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
if (AIUse.getOperandNo() == 1)
ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
} else if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
} else if (CallInst *CI = dyn_cast<CallInst>(U)) {
// This is a call by-value or some other instruction that takes a
// pointer to the variable. Insert a *value* intrinsic that describes
// the variable by dereferencing the alloca.
if (!CI->isLifetimeStartOrEnd()) {
DebugLoc NewLoc = getDebugValueLoc(DDI);
auto *DerefExpr =
DIExpression::append(DDI->getExpression(), dwarf::DW_OP_deref);
insertDbgValueOrDbgVariableRecord(DIB, AI, DDI->getVariable(),
DerefExpr, NewLoc,
CI->getIterator());
}
} else if (BitCastInst *BI = dyn_cast<BitCastInst>(U)) {
if (BI->getType()->isPointerTy())
WorkList.push_back(BI);
}
}
}
DDI->eraseFromParent();
Changed = true;
};
for_each(Dbgs, LowerOne);
for_each(DVRs, LowerOne);
if (Changed)
for (BasicBlock &BB : F)
RemoveRedundantDbgInstrs(&BB);
return Changed;
}
// RemoveDIs: re-implementation of insertDebugValuesForPHIs, but which pulls the
// debug-info out of the block's DbgVariableRecords rather than dbg.value
// intrinsics.
static void
insertDbgVariableRecordsForPHIs(BasicBlock *BB,
SmallVectorImpl<PHINode *> &InsertedPHIs) {
assert(BB && "No BasicBlock to clone DbgVariableRecord(s) from.");
if (InsertedPHIs.size() == 0)
return;
// Map existing PHI nodes to their DbgVariableRecords.
DenseMap<Value *, DbgVariableRecord *> DbgValueMap;
for (auto &I : *BB) {
for (DbgVariableRecord &DVR : filterDbgVars(I.getDbgRecordRange())) {
for (Value *V : DVR.location_ops())
if (auto *Loc = dyn_cast_or_null<PHINode>(V))
DbgValueMap.insert({Loc, &DVR});
}
}
if (DbgValueMap.size() == 0)
return;
// Map a pair of the destination BB and old DbgVariableRecord to the new
// DbgVariableRecord, so that if a DbgVariableRecord is being rewritten to use
// more than one of the inserted PHIs in the same destination BB, we can
// update the same DbgVariableRecord with all the new PHIs instead of creating
// one copy for each.
MapVector<std::pair<BasicBlock *, DbgVariableRecord *>, DbgVariableRecord *>
NewDbgValueMap;
// Then iterate through the new PHIs and look to see if they use one of the
// previously mapped PHIs. If so, create a new DbgVariableRecord that will
// propagate the info through the new PHI. If we use more than one new PHI in
// a single destination BB with the same old dbg.value, merge the updates so
// that we get a single new DbgVariableRecord with all the new PHIs.
for (auto PHI : InsertedPHIs) {
BasicBlock *Parent = PHI->getParent();
// Avoid inserting a debug-info record into an EH block.
if (Parent->getFirstNonPHI()->isEHPad())
continue;
for (auto VI : PHI->operand_values()) {
auto V = DbgValueMap.find(VI);
if (V != DbgValueMap.end()) {
DbgVariableRecord *DbgII = cast<DbgVariableRecord>(V->second);
auto NewDI = NewDbgValueMap.find({Parent, DbgII});
if (NewDI == NewDbgValueMap.end()) {
DbgVariableRecord *NewDbgII = DbgII->clone();
NewDI = NewDbgValueMap.insert({{Parent, DbgII}, NewDbgII}).first;
}
DbgVariableRecord *NewDbgII = NewDI->second;
// If PHI contains VI as an operand more than once, we may
// replaced it in NewDbgII; confirm that it is present.
if (is_contained(NewDbgII->location_ops(), VI))
NewDbgII->replaceVariableLocationOp(VI, PHI);
}
}
}
// Insert the new DbgVariableRecords into their destination blocks.
for (auto DI : NewDbgValueMap) {
BasicBlock *Parent = DI.first.first;
DbgVariableRecord *NewDbgII = DI.second;
auto InsertionPt = Parent->getFirstInsertionPt();
assert(InsertionPt != Parent->end() && "Ill-formed basic block");
Parent->insertDbgRecordBefore(NewDbgII, InsertionPt);
}
}
/// Propagate dbg.value intrinsics through the newly inserted PHIs.
void llvm::insertDebugValuesForPHIs(BasicBlock *BB,
SmallVectorImpl<PHINode *> &InsertedPHIs) {
assert(BB && "No BasicBlock to clone dbg.value(s) from.");
if (InsertedPHIs.size() == 0)
return;
insertDbgVariableRecordsForPHIs(BB, InsertedPHIs);
// Map existing PHI nodes to their dbg.values.
ValueToValueMapTy DbgValueMap;
for (auto &I : *BB) {
if (auto DbgII = dyn_cast<DbgVariableIntrinsic>(&I)) {
for (Value *V : DbgII->location_ops())
if (auto *Loc = dyn_cast_or_null<PHINode>(V))
DbgValueMap.insert({Loc, DbgII});
}
}
if (DbgValueMap.size() == 0)
return;
// Map a pair of the destination BB and old dbg.value to the new dbg.value,
// so that if a dbg.value is being rewritten to use more than one of the
// inserted PHIs in the same destination BB, we can update the same dbg.value
// with all the new PHIs instead of creating one copy for each.
MapVector<std::pair<BasicBlock *, DbgVariableIntrinsic *>,
DbgVariableIntrinsic *>
NewDbgValueMap;
// Then iterate through the new PHIs and look to see if they use one of the
// previously mapped PHIs. If so, create a new dbg.value intrinsic that will
// propagate the info through the new PHI. If we use more than one new PHI in
// a single destination BB with the same old dbg.value, merge the updates so
// that we get a single new dbg.value with all the new PHIs.
for (auto *PHI : InsertedPHIs) {
BasicBlock *Parent = PHI->getParent();
// Avoid inserting an intrinsic into an EH block.
if (Parent->getFirstNonPHI()->isEHPad())
continue;
for (auto *VI : PHI->operand_values()) {
auto V = DbgValueMap.find(VI);
if (V != DbgValueMap.end()) {
auto *DbgII = cast<DbgVariableIntrinsic>(V->second);
auto NewDI = NewDbgValueMap.find({Parent, DbgII});
if (NewDI == NewDbgValueMap.end()) {
auto *NewDbgII = cast<DbgVariableIntrinsic>(DbgII->clone());
NewDI = NewDbgValueMap.insert({{Parent, DbgII}, NewDbgII}).first;
}
DbgVariableIntrinsic *NewDbgII = NewDI->second;
// If PHI contains VI as an operand more than once, we may
// replaced it in NewDbgII; confirm that it is present.
if (is_contained(NewDbgII->location_ops(), VI))
NewDbgII->replaceVariableLocationOp(VI, PHI);
}
}
}
// Insert thew new dbg.values into their destination blocks.
for (auto DI : NewDbgValueMap) {
BasicBlock *Parent = DI.first.first;
auto *NewDbgII = DI.second;
auto InsertionPt = Parent->getFirstInsertionPt();
assert(InsertionPt != Parent->end() && "Ill-formed basic block");
NewDbgII->insertBefore(&*InsertionPt);
}
}
bool llvm::replaceDbgDeclare(Value *Address, Value *NewAddress,
DIBuilder &Builder, uint8_t DIExprFlags,
int Offset) {
TinyPtrVector<DbgDeclareInst *> DbgDeclares = findDbgDeclares(Address);
TinyPtrVector<DbgVariableRecord *> DVRDeclares = findDVRDeclares(Address);
auto ReplaceOne = [&](auto *DII) {
assert(DII->getVariable() && "Missing variable");
auto *DIExpr = DII->getExpression();
DIExpr = DIExpression::prepend(DIExpr, DIExprFlags, Offset);
DII->setExpression(DIExpr);
DII->replaceVariableLocationOp(Address, NewAddress);
};
for_each(DbgDeclares, ReplaceOne);
for_each(DVRDeclares, ReplaceOne);
return !DbgDeclares.empty() || !DVRDeclares.empty();
}
static void updateOneDbgValueForAlloca(const DebugLoc &Loc,
DILocalVariable *DIVar,
DIExpression *DIExpr, Value *NewAddress,
DbgValueInst *DVI,
DbgVariableRecord *DVR,
DIBuilder &Builder, int Offset) {
assert(DIVar && "Missing variable");
// This is an alloca-based dbg.value/DbgVariableRecord. The first thing it
// should do with the alloca pointer is dereference it. Otherwise we don't
// know how to handle it and give up.
if (!DIExpr || DIExpr->getNumElements() < 1 ||
DIExpr->getElement(0) != dwarf::DW_OP_deref)
return;
// Insert the offset before the first deref.
if (Offset)
DIExpr = DIExpression::prepend(DIExpr, 0, Offset);
if (DVI) {
DVI->setExpression(DIExpr);
DVI->replaceVariableLocationOp(0u, NewAddress);
} else {
assert(DVR);
DVR->setExpression(DIExpr);
DVR->replaceVariableLocationOp(0u, NewAddress);
}
}
void llvm::replaceDbgValueForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
DIBuilder &Builder, int Offset) {
SmallVector<DbgValueInst *, 1> DbgUsers;
SmallVector<DbgVariableRecord *, 1> DPUsers;
findDbgValues(DbgUsers, AI, &DPUsers);
// Attempt to replace dbg.values that use this alloca.
for (auto *DVI : DbgUsers)
updateOneDbgValueForAlloca(DVI->getDebugLoc(), DVI->getVariable(),
DVI->getExpression(), NewAllocaAddress, DVI,
nullptr, Builder, Offset);
// Replace any DbgVariableRecords that use this alloca.
for (DbgVariableRecord *DVR : DPUsers)
updateOneDbgValueForAlloca(DVR->getDebugLoc(), DVR->getVariable(),
DVR->getExpression(), NewAllocaAddress, nullptr,
DVR, Builder, Offset);
}
/// Where possible to salvage debug information for \p I do so.
/// If not possible mark undef.
void llvm::salvageDebugInfo(Instruction &I) {
SmallVector<DbgVariableIntrinsic *, 1> DbgUsers;
SmallVector<DbgVariableRecord *, 1> DPUsers;
findDbgUsers(DbgUsers, &I, &DPUsers);
salvageDebugInfoForDbgValues(I, DbgUsers, DPUsers);
}
template <typename T> static void salvageDbgAssignAddress(T *Assign) {
Instruction *I = dyn_cast<Instruction>(Assign->getAddress());
// Only instructions can be salvaged at the moment.
if (!I)
return;
assert(!Assign->getAddressExpression()->getFragmentInfo().has_value() &&
"address-expression shouldn't have fragment info");
// The address component of a dbg.assign cannot be variadic.
uint64_t CurrentLocOps = 0;
SmallVector<Value *, 4> AdditionalValues;
SmallVector<uint64_t, 16> Ops;
Value *NewV = salvageDebugInfoImpl(*I, CurrentLocOps, Ops, AdditionalValues);
// Check if the salvage failed.
if (!NewV)
return;
DIExpression *SalvagedExpr = DIExpression::appendOpsToArg(
Assign->getAddressExpression(), Ops, 0, /*StackValue=*/false);
assert(!SalvagedExpr->getFragmentInfo().has_value() &&
"address-expression shouldn't have fragment info");
// Salvage succeeds if no additional values are required.
if (AdditionalValues.empty()) {
Assign->setAddress(NewV);
Assign->setAddressExpression(SalvagedExpr);
} else {
Assign->setKillAddress();
}
}
void llvm::salvageDebugInfoForDbgValues(
Instruction &I, ArrayRef<DbgVariableIntrinsic *> DbgUsers,
ArrayRef<DbgVariableRecord *> DPUsers) {
// These are arbitrary chosen limits on the maximum number of values and the
// maximum size of a debug expression we can salvage up to, used for
// performance reasons.
const unsigned MaxDebugArgs = 16;
const unsigned MaxExpressionSize = 128;
bool Salvaged = false;
for (auto *DII : DbgUsers) {
if (auto *DAI = dyn_cast<DbgAssignIntrinsic>(DII)) {
if (DAI->getAddress() == &I) {
salvageDbgAssignAddress(DAI);
Salvaged = true;
}
if (DAI->getValue() != &I)
continue;
}
// Do not add DW_OP_stack_value for DbgDeclare, because they are implicitly
// pointing out the value as a DWARF memory location description.
bool StackValue = isa<DbgValueInst>(DII);
auto DIILocation = DII->location_ops();
assert(
is_contained(DIILocation, &I) &&
"DbgVariableIntrinsic must use salvaged instruction as its location");
SmallVector<Value *, 4> AdditionalValues;
// `I` may appear more than once in DII's location ops, and each use of `I`
// must be updated in the DIExpression and potentially have additional
// values added; thus we call salvageDebugInfoImpl for each `I` instance in
// DIILocation.
Value *Op0 = nullptr;
DIExpression *SalvagedExpr = DII->getExpression();
auto LocItr = find(DIILocation, &I);
while (SalvagedExpr && LocItr != DIILocation.end()) {
SmallVector<uint64_t, 16> Ops;
unsigned LocNo = std::distance(DIILocation.begin(), LocItr);
uint64_t CurrentLocOps = SalvagedExpr->getNumLocationOperands();
Op0 = salvageDebugInfoImpl(I, CurrentLocOps, Ops, AdditionalValues);
if (!Op0)
break;
SalvagedExpr =
DIExpression::appendOpsToArg(SalvagedExpr, Ops, LocNo, StackValue);
LocItr = std::find(++LocItr, DIILocation.end(), &I);
}
// salvageDebugInfoImpl should fail on examining the first element of
// DbgUsers, or none of them.
if (!Op0)
break;
DII->replaceVariableLocationOp(&I, Op0);
bool IsValidSalvageExpr = SalvagedExpr->getNumElements() <= MaxExpressionSize;
if (AdditionalValues.empty() && IsValidSalvageExpr) {
DII->setExpression(SalvagedExpr);
} else if (isa<DbgValueInst>(DII) && IsValidSalvageExpr &&
DII->getNumVariableLocationOps() + AdditionalValues.size() <=
MaxDebugArgs) {
DII->addVariableLocationOps(AdditionalValues, SalvagedExpr);
} else {
// Do not salvage using DIArgList for dbg.declare, as it is not currently
// supported in those instructions. Also do not salvage if the resulting
// DIArgList would contain an unreasonably large number of values.
DII->setKillLocation();
}
LLVM_DEBUG(dbgs() << "SALVAGE: " << *DII << '\n');
Salvaged = true;
}
// Duplicate of above block for DbgVariableRecords.
for (auto *DVR : DPUsers) {
if (DVR->isDbgAssign()) {
if (DVR->getAddress() == &I) {
salvageDbgAssignAddress(DVR);
Salvaged = true;
}
if (DVR->getValue() != &I)
continue;
}
// Do not add DW_OP_stack_value for DbgDeclare and DbgAddr, because they
// are implicitly pointing out the value as a DWARF memory location
// description.
bool StackValue =
DVR->getType() != DbgVariableRecord::LocationType::Declare;
auto DVRLocation = DVR->location_ops();
assert(
is_contained(DVRLocation, &I) &&
"DbgVariableIntrinsic must use salvaged instruction as its location");
SmallVector<Value *, 4> AdditionalValues;
// 'I' may appear more than once in DVR's location ops, and each use of 'I'
// must be updated in the DIExpression and potentially have additional
// values added; thus we call salvageDebugInfoImpl for each 'I' instance in
// DVRLocation.
Value *Op0 = nullptr;
DIExpression *SalvagedExpr = DVR->getExpression();
auto LocItr = find(DVRLocation, &I);
while (SalvagedExpr && LocItr != DVRLocation.end()) {
SmallVector<uint64_t, 16> Ops;
unsigned LocNo = std::distance(DVRLocation.begin(), LocItr);
uint64_t CurrentLocOps = SalvagedExpr->getNumLocationOperands();
Op0 = salvageDebugInfoImpl(I, CurrentLocOps, Ops, AdditionalValues);
if (!Op0)
break;
SalvagedExpr =
DIExpression::appendOpsToArg(SalvagedExpr, Ops, LocNo, StackValue);
LocItr = std::find(++LocItr, DVRLocation.end(), &I);
}
// salvageDebugInfoImpl should fail on examining the first element of
// DbgUsers, or none of them.
if (!Op0)
break;
DVR->replaceVariableLocationOp(&I, Op0);
bool IsValidSalvageExpr =
SalvagedExpr->getNumElements() <= MaxExpressionSize;
if (AdditionalValues.empty() && IsValidSalvageExpr) {
DVR->setExpression(SalvagedExpr);
} else if (DVR->getType() != DbgVariableRecord::LocationType::Declare &&
IsValidSalvageExpr &&
DVR->getNumVariableLocationOps() + AdditionalValues.size() <=
MaxDebugArgs) {
DVR->addVariableLocationOps(AdditionalValues, SalvagedExpr);
} else {
// Do not salvage using DIArgList for dbg.addr/dbg.declare, as it is
// currently only valid for stack value expressions.
// Also do not salvage if the resulting DIArgList would contain an
// unreasonably large number of values.
DVR->setKillLocation();
}
LLVM_DEBUG(dbgs() << "SALVAGE: " << DVR << '\n');
Salvaged = true;
}
if (Salvaged)
return;
for (auto *DII : DbgUsers)
DII->setKillLocation();
for (auto *DVR : DPUsers)
DVR->setKillLocation();
}
Value *getSalvageOpsForGEP(GetElementPtrInst *GEP, const DataLayout &DL,
uint64_t CurrentLocOps,
SmallVectorImpl<uint64_t> &Opcodes,
SmallVectorImpl<Value *> &AdditionalValues) {
unsigned BitWidth = DL.getIndexSizeInBits(GEP->getPointerAddressSpace());
// Rewrite a GEP into a DIExpression.
MapVector<Value *, APInt> VariableOffsets;
APInt ConstantOffset(BitWidth, 0);
if (!GEP->collectOffset(DL, BitWidth, VariableOffsets, ConstantOffset))
return nullptr;
if (!VariableOffsets.empty() && !CurrentLocOps) {
Opcodes.insert(Opcodes.begin(), {dwarf::DW_OP_LLVM_arg, 0});
CurrentLocOps = 1;
}
for (const auto &Offset : VariableOffsets) {
AdditionalValues.push_back(Offset.first);
assert(Offset.second.isStrictlyPositive() &&
"Expected strictly positive multiplier for offset.");
Opcodes.append({dwarf::DW_OP_LLVM_arg, CurrentLocOps++, dwarf::DW_OP_constu,
Offset.second.getZExtValue(), dwarf::DW_OP_mul,
dwarf::DW_OP_plus});
}
DIExpression::appendOffset(Opcodes, ConstantOffset.getSExtValue());
return GEP->getOperand(0);
}
uint64_t getDwarfOpForBinOp(Instruction::BinaryOps Opcode) {
switch (Opcode) {
case Instruction::Add:
return dwarf::DW_OP_plus;
case Instruction::Sub:
return dwarf::DW_OP_minus;
case Instruction::Mul:
return dwarf::DW_OP_mul;
case Instruction::SDiv:
return dwarf::DW_OP_div;
case Instruction::SRem:
return dwarf::DW_OP_mod;
case Instruction::Or:
return dwarf::DW_OP_or;
case Instruction::And:
return dwarf::DW_OP_and;
case Instruction::Xor:
return dwarf::DW_OP_xor;
case Instruction::Shl:
return dwarf::DW_OP_shl;
case Instruction::LShr:
return dwarf::DW_OP_shr;
case Instruction::AShr:
return dwarf::DW_OP_shra;
default:
// TODO: Salvage from each kind of binop we know about.
return 0;
}
}
static void handleSSAValueOperands(uint64_t CurrentLocOps,
SmallVectorImpl<uint64_t> &Opcodes,
SmallVectorImpl<Value *> &AdditionalValues,
Instruction *I) {
if (!CurrentLocOps) {
Opcodes.append({dwarf::DW_OP_LLVM_arg, 0});
CurrentLocOps = 1;
}
Opcodes.append({dwarf::DW_OP_LLVM_arg, CurrentLocOps});
AdditionalValues.push_back(I->getOperand(1));
}
Value *getSalvageOpsForBinOp(BinaryOperator *BI, uint64_t CurrentLocOps,
SmallVectorImpl<uint64_t> &Opcodes,
SmallVectorImpl<Value *> &AdditionalValues) {
// Handle binary operations with constant integer operands as a special case.
auto *ConstInt = dyn_cast<ConstantInt>(BI->getOperand(1));
// Values wider than 64 bits cannot be represented within a DIExpression.
if (ConstInt && ConstInt->getBitWidth() > 64)
return nullptr;
Instruction::BinaryOps BinOpcode = BI->getOpcode();
// Push any Constant Int operand onto the expression stack.
if (ConstInt) {
uint64_t Val = ConstInt->getSExtValue();
// Add or Sub Instructions with a constant operand can potentially be
// simplified.
if (BinOpcode == Instruction::Add || BinOpcode == Instruction::Sub) {
uint64_t Offset = BinOpcode == Instruction::Add ? Val : -int64_t(Val);
DIExpression::appendOffset(Opcodes, Offset);
return BI->getOperand(0);
}
Opcodes.append({dwarf::DW_OP_constu, Val});
} else {
handleSSAValueOperands(CurrentLocOps, Opcodes, AdditionalValues, BI);
}
// Add salvaged binary operator to expression stack, if it has a valid
// representation in a DIExpression.
uint64_t DwarfBinOp = getDwarfOpForBinOp(BinOpcode);
if (!DwarfBinOp)
return nullptr;
Opcodes.push_back(DwarfBinOp);
return BI->getOperand(0);
}
uint64_t getDwarfOpForIcmpPred(CmpInst::Predicate Pred) {
// The signedness of the operation is implicit in the typed stack, signed and
// unsigned instructions map to the same DWARF opcode.
switch (Pred) {
case CmpInst::ICMP_EQ:
return dwarf::DW_OP_eq;
case CmpInst::ICMP_NE:
return dwarf::DW_OP_ne;
case CmpInst::ICMP_UGT:
case CmpInst::ICMP_SGT:
return dwarf::DW_OP_gt;
case CmpInst::ICMP_UGE:
case CmpInst::ICMP_SGE:
return dwarf::DW_OP_ge;
case CmpInst::ICMP_ULT:
case CmpInst::ICMP_SLT:
return dwarf::DW_OP_lt;
case CmpInst::ICMP_ULE:
case CmpInst::ICMP_SLE:
return dwarf::DW_OP_le;
default:
return 0;
}
}
Value *getSalvageOpsForIcmpOp(ICmpInst *Icmp, uint64_t CurrentLocOps,
SmallVectorImpl<uint64_t> &Opcodes,
SmallVectorImpl<Value *> &AdditionalValues) {
// Handle icmp operations with constant integer operands as a special case.
auto *ConstInt = dyn_cast<ConstantInt>(Icmp->getOperand(1));
// Values wider than 64 bits cannot be represented within a DIExpression.
if (ConstInt && ConstInt->getBitWidth() > 64)
return nullptr;
// Push any Constant Int operand onto the expression stack.
if (ConstInt) {
if (Icmp->isSigned())
Opcodes.push_back(dwarf::DW_OP_consts);
else
Opcodes.push_back(dwarf::DW_OP_constu);
uint64_t Val = ConstInt->getSExtValue();
Opcodes.push_back(Val);
} else {
handleSSAValueOperands(CurrentLocOps, Opcodes, AdditionalValues, Icmp);
}
// Add salvaged binary operator to expression stack, if it has a valid
// representation in a DIExpression.
uint64_t DwarfIcmpOp = getDwarfOpForIcmpPred(Icmp->getPredicate());
if (!DwarfIcmpOp)
return nullptr;
Opcodes.push_back(DwarfIcmpOp);
return Icmp->getOperand(0);
}
Value *llvm::salvageDebugInfoImpl(Instruction &I, uint64_t CurrentLocOps,
SmallVectorImpl<uint64_t> &Ops,
SmallVectorImpl<Value *> &AdditionalValues) {
auto &M = *I.getModule();
auto &DL = M.getDataLayout();
if (auto *CI = dyn_cast<CastInst>(&I)) {
Value *FromValue = CI->getOperand(0);
// No-op casts are irrelevant for debug info.
if (CI->isNoopCast(DL)) {
return FromValue;
}
Type *Type = CI->getType();
if (Type->isPointerTy())
Type = DL.getIntPtrType(Type);
// Casts other than Trunc, SExt, or ZExt to scalar types cannot be salvaged.
if (Type->isVectorTy() ||
!(isa<TruncInst>(&I) || isa<SExtInst>(&I) || isa<ZExtInst>(&I) ||
isa<IntToPtrInst>(&I) || isa<PtrToIntInst>(&I)))
return nullptr;
llvm::Type *FromType = FromValue->getType();
if (FromType->isPointerTy())
FromType = DL.getIntPtrType(FromType);
unsigned FromTypeBitSize = FromType->getScalarSizeInBits();
unsigned ToTypeBitSize = Type->getScalarSizeInBits();
auto ExtOps = DIExpression::getExtOps(FromTypeBitSize, ToTypeBitSize,
isa<SExtInst>(&I));
Ops.append(ExtOps.begin(), ExtOps.end());
return FromValue;
}
if (auto *GEP = dyn_cast<GetElementPtrInst>(&I))
return getSalvageOpsForGEP(GEP, DL, CurrentLocOps, Ops, AdditionalValues);
if (auto *BI = dyn_cast<BinaryOperator>(&I))
return getSalvageOpsForBinOp(BI, CurrentLocOps, Ops, AdditionalValues);
if (auto *IC = dyn_cast<ICmpInst>(&I))
return getSalvageOpsForIcmpOp(IC, CurrentLocOps, Ops, AdditionalValues);
// *Not* to do: we should not attempt to salvage load instructions,
// because the validity and lifetime of a dbg.value containing
// DW_OP_deref becomes difficult to analyze. See PR40628 for examples.
return nullptr;
}
/// A replacement for a dbg.value expression.
using DbgValReplacement = std::optional<DIExpression *>;
/// Point debug users of \p From to \p To using exprs given by \p RewriteExpr,
/// possibly moving/undefing users to prevent use-before-def. Returns true if
/// changes are made.
static bool rewriteDebugUsers(
Instruction &From, Value &To, Instruction &DomPoint, DominatorTree &DT,
function_ref<DbgValReplacement(DbgVariableIntrinsic &DII)> RewriteExpr,
function_ref<DbgValReplacement(DbgVariableRecord &DVR)> RewriteDVRExpr) {
// Find debug users of From.
SmallVector<DbgVariableIntrinsic *, 1> Users;
SmallVector<DbgVariableRecord *, 1> DPUsers;
findDbgUsers(Users, &From, &DPUsers);
if (Users.empty() && DPUsers.empty())
return false;
// Prevent use-before-def of To.
bool Changed = false;
SmallPtrSet<DbgVariableIntrinsic *, 1> UndefOrSalvage;
SmallPtrSet<DbgVariableRecord *, 1> UndefOrSalvageDVR;
if (isa<Instruction>(&To)) {
bool DomPointAfterFrom = From.getNextNonDebugInstruction() == &DomPoint;
for (auto *DII : Users) {
// It's common to see a debug user between From and DomPoint. Move it
// after DomPoint to preserve the variable update without any reordering.
if (DomPointAfterFrom && DII->getNextNonDebugInstruction() == &DomPoint) {
LLVM_DEBUG(dbgs() << "MOVE: " << *DII << '\n');
DII->moveAfter(&DomPoint);
Changed = true;
// Users which otherwise aren't dominated by the replacement value must
// be salvaged or deleted.
} else if (!DT.dominates(&DomPoint, DII)) {
UndefOrSalvage.insert(DII);
}
}
// DbgVariableRecord implementation of the above.
for (auto *DVR : DPUsers) {
Instruction *MarkedInstr = DVR->getMarker()->MarkedInstr;
Instruction *NextNonDebug = MarkedInstr;
// The next instruction might still be a dbg.declare, skip over it.
if (isa<DbgVariableIntrinsic>(NextNonDebug))
NextNonDebug = NextNonDebug->getNextNonDebugInstruction();
if (DomPointAfterFrom && NextNonDebug == &DomPoint) {
LLVM_DEBUG(dbgs() << "MOVE: " << *DVR << '\n');
DVR->removeFromParent();
// Ensure there's a marker.
DomPoint.getParent()->insertDbgRecordAfter(DVR, &DomPoint);
Changed = true;
} else if (!DT.dominates(&DomPoint, MarkedInstr)) {
UndefOrSalvageDVR.insert(DVR);
}
}
}
// Update debug users without use-before-def risk.
for (auto *DII : Users) {
if (UndefOrSalvage.count(DII))
continue;
DbgValReplacement DVRepl = RewriteExpr(*DII);
if (!DVRepl)
continue;
DII->replaceVariableLocationOp(&From, &To);
DII->setExpression(*DVRepl);
LLVM_DEBUG(dbgs() << "REWRITE: " << *DII << '\n');
Changed = true;
}
for (auto *DVR : DPUsers) {
if (UndefOrSalvageDVR.count(DVR))
continue;
DbgValReplacement DVRepl = RewriteDVRExpr(*DVR);
if (!DVRepl)
continue;
DVR->replaceVariableLocationOp(&From, &To);
DVR->setExpression(*DVRepl);
LLVM_DEBUG(dbgs() << "REWRITE: " << DVR << '\n');
Changed = true;
}
if (!UndefOrSalvage.empty() || !UndefOrSalvageDVR.empty()) {
// Try to salvage the remaining debug users.
salvageDebugInfo(From);
Changed = true;
}
return Changed;
}
/// Check if a bitcast between a value of type \p FromTy to type \p ToTy would
/// losslessly preserve the bits and semantics of the value. This predicate is
/// symmetric, i.e swapping \p FromTy and \p ToTy should give the same result.
///
/// Note that Type::canLosslesslyBitCastTo is not suitable here because it
/// allows semantically unequivalent bitcasts, such as <2 x i64> -> <4 x i32>,
/// and also does not allow lossless pointer <-> integer conversions.
static bool isBitCastSemanticsPreserving(const DataLayout &DL, Type *FromTy,
Type *ToTy) {
// Trivially compatible types.
if (FromTy == ToTy)
return true;
// Handle compatible pointer <-> integer conversions.
if (FromTy->isIntOrPtrTy() && ToTy->isIntOrPtrTy()) {
bool SameSize = DL.getTypeSizeInBits(FromTy) == DL.getTypeSizeInBits(ToTy);
bool LosslessConversion = !DL.isNonIntegralPointerType(FromTy) &&
!DL.isNonIntegralPointerType(ToTy);
return SameSize && LosslessConversion;
}
// TODO: This is not exhaustive.
return false;
}
bool llvm::replaceAllDbgUsesWith(Instruction &From, Value &To,
Instruction &DomPoint, DominatorTree &DT) {
// Exit early if From has no debug users.
if (!From.isUsedByMetadata())
return false;
assert(&From != &To && "Can't replace something with itself");
Type *FromTy = From.getType();
Type *ToTy = To.getType();
auto Identity = [&](DbgVariableIntrinsic &DII) -> DbgValReplacement {
return DII.getExpression();
};
auto IdentityDVR = [&](DbgVariableRecord &DVR) -> DbgValReplacement {
return DVR.getExpression();
};
// Handle no-op conversions.
Module &M = *From.getModule();
const DataLayout &DL = M.getDataLayout();
if (isBitCastSemanticsPreserving(DL, FromTy, ToTy))
return rewriteDebugUsers(From, To, DomPoint, DT, Identity, IdentityDVR);
// Handle integer-to-integer widening and narrowing.
// FIXME: Use DW_OP_convert when it's available everywhere.
if (FromTy->isIntegerTy() && ToTy->isIntegerTy()) {
uint64_t FromBits = FromTy->getPrimitiveSizeInBits();
uint64_t ToBits = ToTy->getPrimitiveSizeInBits();
assert(FromBits != ToBits && "Unexpected no-op conversion");
// When the width of the result grows, assume that a debugger will only
// access the low `FromBits` bits when inspecting the source variable.
if (FromBits < ToBits)
return rewriteDebugUsers(From, To, DomPoint, DT, Identity, IdentityDVR);