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//===--- CGStmt.cpp - Emit LLVM Code from Statements ----------------------===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This contains code to emit Stmt nodes as LLVM code.
#include "CGDebugInfo.h"
#include "CodeGenModule.h"
#include "CodeGenFunction.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/Basic/PrettyStackTrace.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/InlineAsm.h"
#include "llvm/Intrinsics.h"
#include "llvm/Target/TargetData.h"
using namespace clang;
using namespace CodeGen;
// Statement Emission
void CodeGenFunction::EmitStopPoint(const Stmt *S) {
if (CGDebugInfo *DI = getDebugInfo()) {
DI->EmitStopPoint(CurFn, Builder);
void CodeGenFunction::EmitStmt(const Stmt *S) {
assert(S && "Null statement?");
// Check if we can handle this without bothering to generate an
// insert point or debug info.
if (EmitSimpleStmt(S))
// Check if we are generating unreachable code.
if (!HaveInsertPoint()) {
// If so, and the statement doesn't contain a label, then we do not need to
// generate actual code. This is safe because (1) the current point is
// unreachable, so we don't need to execute the code, and (2) we've already
// handled the statements which update internal data structures (like the
// local variable map) which could be used by subsequent statements.
if (!ContainsLabel(S)) {
// Verify that any decl statements were handled as simple, they may be in
// scope of subsequent reachable statements.
assert(!isa<DeclStmt>(*S) && "Unexpected DeclStmt!");
// Otherwise, make a new block to hold the code.
// Generate a stoppoint if we are emitting debug info.
switch (S->getStmtClass()) {
// Must be an expression in a stmt context. Emit the value (to get
// side-effects) and ignore the result.
if (!isa<Expr>(S))
ErrorUnsupported(S, "statement");
EmitAnyExpr(cast<Expr>(S), 0, false, true);
// Expression emitters don't handle unreachable blocks yet, so look for one
// explicitly here. This handles the common case of a call to a noreturn
// function.
if (llvm::BasicBlock *CurBB = Builder.GetInsertBlock()) {
if (CurBB->empty() && CurBB->use_empty()) {
case Stmt::IndirectGotoStmtClass:
EmitIndirectGotoStmt(cast<IndirectGotoStmt>(*S)); break;
case Stmt::IfStmtClass: EmitIfStmt(cast<IfStmt>(*S)); break;
case Stmt::WhileStmtClass: EmitWhileStmt(cast<WhileStmt>(*S)); break;
case Stmt::DoStmtClass: EmitDoStmt(cast<DoStmt>(*S)); break;
case Stmt::ForStmtClass: EmitForStmt(cast<ForStmt>(*S)); break;
case Stmt::ReturnStmtClass: EmitReturnStmt(cast<ReturnStmt>(*S)); break;
case Stmt::SwitchStmtClass: EmitSwitchStmt(cast<SwitchStmt>(*S)); break;
case Stmt::AsmStmtClass: EmitAsmStmt(cast<AsmStmt>(*S)); break;
case Stmt::ObjCAtTryStmtClass:
case Stmt::ObjCAtCatchStmtClass:
assert(0 && "@catch statements should be handled by EmitObjCAtTryStmt");
case Stmt::ObjCAtFinallyStmtClass:
assert(0 && "@finally statements should be handled by EmitObjCAtTryStmt");
case Stmt::ObjCAtThrowStmtClass:
case Stmt::ObjCAtSynchronizedStmtClass:
case Stmt::ObjCForCollectionStmtClass:
case Stmt::CXXTryStmtClass:
bool CodeGenFunction::EmitSimpleStmt(const Stmt *S) {
switch (S->getStmtClass()) {
default: return false;
case Stmt::NullStmtClass: break;
case Stmt::CompoundStmtClass: EmitCompoundStmt(cast<CompoundStmt>(*S)); break;
case Stmt::DeclStmtClass: EmitDeclStmt(cast<DeclStmt>(*S)); break;
case Stmt::LabelStmtClass: EmitLabelStmt(cast<LabelStmt>(*S)); break;
case Stmt::GotoStmtClass: EmitGotoStmt(cast<GotoStmt>(*S)); break;
case Stmt::BreakStmtClass: EmitBreakStmt(cast<BreakStmt>(*S)); break;
case Stmt::ContinueStmtClass: EmitContinueStmt(cast<ContinueStmt>(*S)); break;
case Stmt::DefaultStmtClass: EmitDefaultStmt(cast<DefaultStmt>(*S)); break;
case Stmt::CaseStmtClass: EmitCaseStmt(cast<CaseStmt>(*S)); break;
return true;
/// EmitCompoundStmt - Emit a compound statement {..} node. If GetLast is true,
/// this captures the expression result of the last sub-statement and returns it
/// (for use by the statement expression extension).
RValue CodeGenFunction::EmitCompoundStmt(const CompoundStmt &S, bool GetLast,
llvm::Value *AggLoc, bool isAggVol) {
PrettyStackTraceLoc CrashInfo(getContext().getSourceManager(),S.getLBracLoc(),
"LLVM IR generation of compound statement ('{}')");
CGDebugInfo *DI = getDebugInfo();
if (DI) {
DI->EmitRegionStart(CurFn, Builder);
// Keep track of the current cleanup stack depth.
CleanupScope Scope(*this);
for (CompoundStmt::const_body_iterator I = S.body_begin(),
E = S.body_end()-GetLast; I != E; ++I)
if (DI) {
DI->EmitRegionEnd(CurFn, Builder);
RValue RV;
if (!GetLast)
RV = RValue::get(0);
else {
// We have to special case labels here. They are statements, but when put
// at the end of a statement expression, they yield the value of their
// subexpression. Handle this by walking through all labels we encounter,
// emitting them before we evaluate the subexpr.
const Stmt *LastStmt = S.body_back();
while (const LabelStmt *LS = dyn_cast<LabelStmt>(LastStmt)) {
LastStmt = LS->getSubStmt();
RV = EmitAnyExpr(cast<Expr>(LastStmt), AggLoc);
return RV;
void CodeGenFunction::SimplifyForwardingBlocks(llvm::BasicBlock *BB) {
llvm::BranchInst *BI = dyn_cast<llvm::BranchInst>(BB->getTerminator());
// If there is a cleanup stack, then we it isn't worth trying to
// simplify this block (we would need to remove it from the scope map
// and cleanup entry).
if (!CleanupEntries.empty())
// Can only simplify direct branches.
if (!BI || !BI->isUnconditional())
void CodeGenFunction::EmitBlock(llvm::BasicBlock *BB, bool IsFinished) {
// Fall out of the current block (if necessary).
if (IsFinished && BB->use_empty()) {
delete BB;
// If necessary, associate the block with the cleanup stack size.
if (!CleanupEntries.empty()) {
// Check if the basic block has already been inserted.
BlockScopeMap::iterator I = BlockScopes.find(BB);
if (I != BlockScopes.end()) {
assert(I->second == CleanupEntries.size() - 1);
} else {
BlockScopes[BB] = CleanupEntries.size() - 1;
void CodeGenFunction::EmitBranch(llvm::BasicBlock *Target) {
// Emit a branch from the current block to the target one if this
// was a real block. If this was just a fall-through block after a
// terminator, don't emit it.
llvm::BasicBlock *CurBB = Builder.GetInsertBlock();
if (!CurBB || CurBB->getTerminator()) {
// If there is no insert point or the previous block is already
// terminated, don't touch it.
} else {
// Otherwise, create a fall-through branch.
void CodeGenFunction::EmitLabel(const LabelStmt &S) {
void CodeGenFunction::EmitLabelStmt(const LabelStmt &S) {
void CodeGenFunction::EmitGotoStmt(const GotoStmt &S) {
// If this code is reachable then emit a stop point (if generating
// debug info). We have to do this ourselves because we are on the
// "simple" statement path.
if (HaveInsertPoint())
void CodeGenFunction::EmitIndirectGotoStmt(const IndirectGotoStmt &S) {
// Ensure that we have an i8* for our PHI node.
llvm::Value *V = Builder.CreateBitCast(EmitScalarExpr(S.getTarget()),
llvm::BasicBlock *CurBB = Builder.GetInsertBlock();
// Get the basic block for the indirect goto.
llvm::BasicBlock *IndGotoBB = GetIndirectGotoBlock();
// The first instruction in the block has to be the PHI for the switch dest,
// add an entry for this branch.
cast<llvm::PHINode>(IndGotoBB->begin())->addIncoming(V, CurBB);
void CodeGenFunction::EmitIfStmt(const IfStmt &S) {
// C99 The first substatement is executed if the expression compares
// unequal to 0. The condition must be a scalar type.
CleanupScope ConditionScope(*this);
if (S.getConditionVariable())
// If the condition constant folds and can be elided, try to avoid emitting
// the condition and the dead arm of the if/else.
if (int Cond = ConstantFoldsToSimpleInteger(S.getCond())) {
// Figure out which block (then or else) is executed.
const Stmt *Executed = S.getThen(), *Skipped = S.getElse();
if (Cond == -1) // Condition false?
std::swap(Executed, Skipped);
// If the skipped block has no labels in it, just emit the executed block.
// This avoids emitting dead code and simplifies the CFG substantially.
if (!ContainsLabel(Skipped)) {
if (Executed) {
CleanupScope ExecutedScope(*this);
// Otherwise, the condition did not fold, or we couldn't elide it. Just emit
// the conditional branch.
llvm::BasicBlock *ThenBlock = createBasicBlock("if.then");
llvm::BasicBlock *ContBlock = createBasicBlock("if.end");
llvm::BasicBlock *ElseBlock = ContBlock;
if (S.getElse())
ElseBlock = createBasicBlock("if.else");
EmitBranchOnBoolExpr(S.getCond(), ThenBlock, ElseBlock);
// Emit the 'then' code.
CleanupScope ThenScope(*this);
// Emit the 'else' code if present.
if (const Stmt *Else = S.getElse()) {
CleanupScope ElseScope(*this);
// Emit the continuation block for code after the if.
EmitBlock(ContBlock, true);
void CodeGenFunction::EmitWhileStmt(const WhileStmt &S) {
// Emit the header for the loop, insert it, which will create an uncond br to
// it.
llvm::BasicBlock *LoopHeader = createBasicBlock("while.cond");
// Create an exit block for when the condition fails, create a block for the
// body of the loop.
llvm::BasicBlock *ExitBlock = createBasicBlock("while.end");
llvm::BasicBlock *LoopBody = createBasicBlock("while.body");
llvm::BasicBlock *CleanupBlock = 0;
llvm::BasicBlock *EffectiveExitBlock = ExitBlock;
// Store the blocks to use for break and continue.
BreakContinueStack.push_back(BreakContinue(ExitBlock, LoopHeader));
// C++ [stmt.while]p2:
// When the condition of a while statement is a declaration, the
// scope of the variable that is declared extends from its point
// of declaration (3.3.2) to the end of the while statement.
// [...]
// The object created in a condition is destroyed and created
// with each iteration of the loop.
CleanupScope ConditionScope(*this);
if (S.getConditionVariable()) {
// If this condition variable requires cleanups, create a basic
// block to handle those cleanups.
if (ConditionScope.requiresCleanups()) {
CleanupBlock = createBasicBlock("while.cleanup");
EffectiveExitBlock = CleanupBlock;
// Evaluate the conditional in the while header. C99 The
// evaluation of the controlling expression takes place before each
// execution of the loop body.
llvm::Value *BoolCondVal = EvaluateExprAsBool(S.getCond());
// while(1) is common, avoid extra exit blocks. Be sure
// to correctly handle break/continue though.
bool EmitBoolCondBranch = true;
if (llvm::ConstantInt *C = dyn_cast<llvm::ConstantInt>(BoolCondVal))
if (C->isOne())
EmitBoolCondBranch = false;
// As long as the condition is true, go to the loop body.
if (EmitBoolCondBranch)
Builder.CreateCondBr(BoolCondVal, LoopBody, EffectiveExitBlock);
// Emit the loop body.
CleanupScope BodyScope(*this);
if (CleanupBlock) {
// If we have a cleanup block, jump there to perform cleanups
// before looping.
// Emit the cleanup block, performing cleanups for the condition
// and then jumping to either the loop header or the exit block.
Builder.CreateCondBr(BoolCondVal, LoopHeader, ExitBlock);
} else {
// Cycle to the condition.
// Emit the exit block.
EmitBlock(ExitBlock, true);
// The LoopHeader typically is just a branch if we skipped emitting
// a branch, try to erase it.
if (!EmitBoolCondBranch && !CleanupBlock)
void CodeGenFunction::EmitDoStmt(const DoStmt &S) {
// Emit the body for the loop, insert it, which will create an uncond br to
// it.
llvm::BasicBlock *LoopBody = createBasicBlock("do.body");
llvm::BasicBlock *AfterDo = createBasicBlock("do.end");
llvm::BasicBlock *DoCond = createBasicBlock("do.cond");
// Store the blocks to use for break and continue.
BreakContinueStack.push_back(BreakContinue(AfterDo, DoCond));
// Emit the body of the loop into the block.
// C99 "The evaluation of the controlling expression takes place
// after each execution of the loop body."
// Evaluate the conditional in the while header.
// C99 6.8.5p2/p4: The first substatement is executed if the expression
// compares unequal to 0. The condition must be a scalar type.
llvm::Value *BoolCondVal = EvaluateExprAsBool(S.getCond());
// "do {} while (0)" is common in macros, avoid extra blocks. Be sure
// to correctly handle break/continue though.
bool EmitBoolCondBranch = true;
if (llvm::ConstantInt *C = dyn_cast<llvm::ConstantInt>(BoolCondVal))
if (C->isZero())
EmitBoolCondBranch = false;
// As long as the condition is true, iterate the loop.
if (EmitBoolCondBranch)
Builder.CreateCondBr(BoolCondVal, LoopBody, AfterDo);
// Emit the exit block.
// The DoCond block typically is just a branch if we skipped
// emitting a branch, try to erase it.
if (!EmitBoolCondBranch)
void CodeGenFunction::EmitForStmt(const ForStmt &S) {
// FIXME: What do we do if the increment (f.e.) contains a stmt expression,
// which contains a continue/break?
CleanupScope ForScope(*this);
// Evaluate the first part before the loop.
if (S.getInit())
// Start the loop with a block that tests the condition.
llvm::BasicBlock *CondBlock = createBasicBlock("for.cond");
llvm::BasicBlock *AfterFor = createBasicBlock("for.end");
llvm::BasicBlock *IncBlock = 0;
llvm::BasicBlock *CondCleanup = 0;
llvm::BasicBlock *EffectiveExitBlock = AfterFor;
// Create a cleanup scope for the condition variable cleanups.
CleanupScope ConditionScope(*this);
llvm::Value *BoolCondVal = 0;
if (S.getCond()) {
// If the for statement has a condition scope, emit the local variable
// declaration.
if (S.getConditionVariable()) {
if (ConditionScope.requiresCleanups()) {
CondCleanup = createBasicBlock("for.cond.cleanup");
EffectiveExitBlock = CondCleanup;
// As long as the condition is true, iterate the loop.
llvm::BasicBlock *ForBody = createBasicBlock("for.body");
// C99 6.8.5p2/p4: The first substatement is executed if the expression
// compares unequal to 0. The condition must be a scalar type.
BoolCondVal = EvaluateExprAsBool(S.getCond());
Builder.CreateCondBr(BoolCondVal, ForBody, EffectiveExitBlock);
} else {
// Treat it as a non-zero constant. Don't even create a new block for the
// body, just fall into it.
// If the for loop doesn't have an increment we can just use the
// condition as the continue block.
llvm::BasicBlock *ContinueBlock;
if (S.getInc())
ContinueBlock = IncBlock = createBasicBlock("");
ContinueBlock = CondBlock;
// Store the blocks to use for break and continue.
BreakContinueStack.push_back(BreakContinue(AfterFor, ContinueBlock));
// If the condition is true, execute the body of the for stmt.
CGDebugInfo *DI = getDebugInfo();
if (DI) {
DI->EmitRegionStart(CurFn, Builder);
// Create a separate cleanup scope for the body, in case it is not
// a compound statement.
CleanupScope BodyScope(*this);
// If there is an increment, emit it next.
if (S.getInc()) {
// Finally, branch back up to the condition for the next iteration.
if (CondCleanup) {
// Branch to the cleanup block.
// Emit the cleanup block, which branches back to the loop body or
// outside of the for statement once it is done.
Builder.CreateCondBr(BoolCondVal, CondBlock, AfterFor);
} else
if (DI) {
DI->EmitRegionEnd(CurFn, Builder);
// Emit the fall-through block.
EmitBlock(AfterFor, true);
void CodeGenFunction::EmitReturnOfRValue(RValue RV, QualType Ty) {
if (RV.isScalar()) {
Builder.CreateStore(RV.getScalarVal(), ReturnValue);
} else if (RV.isAggregate()) {
EmitAggregateCopy(ReturnValue, RV.getAggregateAddr(), Ty);
} else {
StoreComplexToAddr(RV.getComplexVal(), ReturnValue, false);
/// EmitReturnStmt - Note that due to GCC extensions, this can have an operand
/// if the function returns void, or may be missing one if the function returns
/// non-void. Fun stuff :).
void CodeGenFunction::EmitReturnStmt(const ReturnStmt &S) {
// Emit the result value, even if unused, to evalute the side effects.
const Expr *RV = S.getRetValue();
// FIXME: Clean this up by using an LValue for ReturnTemp,
// EmitStoreThroughLValue, and EmitAnyExpr.
if (!ReturnValue) {
// Make sure not to return anything, but evaluate the expression
// for side effects.
if (RV)
} else if (RV == 0) {
// Do nothing (return value is left uninitialized)
} else if (FnRetTy->isReferenceType()) {
// If this function returns a reference, take the address of the expression
// rather than the value.
Builder.CreateStore(EmitLValue(RV).getAddress(), ReturnValue);
} else if (!hasAggregateLLVMType(RV->getType())) {
Builder.CreateStore(EmitScalarExpr(RV), ReturnValue);
} else if (RV->getType()->isAnyComplexType()) {
EmitComplexExprIntoAddr(RV, ReturnValue, false);
} else {
EmitAggExpr(RV, ReturnValue, false);
void CodeGenFunction::EmitDeclStmt(const DeclStmt &S) {
// As long as debug info is modeled with instructions, we have to ensure we
// have a place to insert here and write the stop point here.
if (getDebugInfo()) {
for (DeclStmt::const_decl_iterator I = S.decl_begin(), E = S.decl_end();
I != E; ++I)
void CodeGenFunction::EmitBreakStmt(const BreakStmt &S) {
assert(!BreakContinueStack.empty() && "break stmt not in a loop or switch!");
// If this code is reachable then emit a stop point (if generating
// debug info). We have to do this ourselves because we are on the
// "simple" statement path.
if (HaveInsertPoint())
llvm::BasicBlock *Block = BreakContinueStack.back().BreakBlock;
void CodeGenFunction::EmitContinueStmt(const ContinueStmt &S) {
assert(!BreakContinueStack.empty() && "continue stmt not in a loop!");
// If this code is reachable then emit a stop point (if generating
// debug info). We have to do this ourselves because we are on the
// "simple" statement path.
if (HaveInsertPoint())
llvm::BasicBlock *Block = BreakContinueStack.back().ContinueBlock;
/// EmitCaseStmtRange - If case statement range is not too big then
/// add multiple cases to switch instruction, one for each value within
/// the range. If range is too big then emit "if" condition check.
void CodeGenFunction::EmitCaseStmtRange(const CaseStmt &S) {
assert(S.getRHS() && "Expected RHS value in CaseStmt");
llvm::APSInt LHS = S.getLHS()->EvaluateAsInt(getContext());
llvm::APSInt RHS = S.getRHS()->EvaluateAsInt(getContext());
// Emit the code for this case. We do this first to make sure it is
// properly chained from our predecessor before generating the
// switch machinery to enter this block.
llvm::BasicBlock *CaseDest = Builder.GetInsertBlock();
// If range is empty, do nothing.
if (LHS.isSigned() ? RHS.slt(LHS) : RHS.ult(LHS))
llvm::APInt Range = RHS - LHS;
// FIXME: parameters such as this should not be hardcoded.
if (Range.ult(llvm::APInt(Range.getBitWidth(), 64))) {
// Range is small enough to add multiple switch instruction cases.
for (unsigned i = 0, e = Range.getZExtValue() + 1; i != e; ++i) {
SwitchInsn->addCase(llvm::ConstantInt::get(VMContext, LHS), CaseDest);
// The range is too big. Emit "if" condition into a new block,
// making sure to save and restore the current insertion point.
llvm::BasicBlock *RestoreBB = Builder.GetInsertBlock();
// Push this test onto the chain of range checks (which terminates
// in the default basic block). The switch's default will be changed
// to the top of this chain after switch emission is complete.
llvm::BasicBlock *FalseDest = CaseRangeBlock;
CaseRangeBlock = createBasicBlock("sw.caserange");
// Emit range check.
llvm::Value *Diff =
llvm::ConstantInt::get(VMContext, LHS), "tmp");
llvm::Value *Cond =
llvm::ConstantInt::get(VMContext, Range), "tmp");
Builder.CreateCondBr(Cond, CaseDest, FalseDest);
// Restore the appropriate insertion point.
if (RestoreBB)
void CodeGenFunction::EmitCaseStmt(const CaseStmt &S) {
if (S.getRHS()) {
llvm::BasicBlock *CaseDest = Builder.GetInsertBlock();
llvm::APSInt CaseVal = S.getLHS()->EvaluateAsInt(getContext());
SwitchInsn->addCase(llvm::ConstantInt::get(VMContext, CaseVal), CaseDest);
// Recursively emitting the statement is acceptable, but is not wonderful for
// code where we have many case statements nested together, i.e.:
// case 1:
// case 2:
// case 3: etc.
// Handling this recursively will create a new block for each case statement
// that falls through to the next case which is IR intensive. It also causes
// deep recursion which can run into stack depth limitations. Handle
// sequential non-range case statements specially.
const CaseStmt *CurCase = &S;
const CaseStmt *NextCase = dyn_cast<CaseStmt>(S.getSubStmt());
// Otherwise, iteratively add consequtive cases to this switch stmt.
while (NextCase && NextCase->getRHS() == 0) {
CurCase = NextCase;
CaseVal = CurCase->getLHS()->EvaluateAsInt(getContext());
SwitchInsn->addCase(llvm::ConstantInt::get(VMContext, CaseVal), CaseDest);
NextCase = dyn_cast<CaseStmt>(CurCase->getSubStmt());
// Normal default recursion for non-cases.
void CodeGenFunction::EmitDefaultStmt(const DefaultStmt &S) {
llvm::BasicBlock *DefaultBlock = SwitchInsn->getDefaultDest();
assert(DefaultBlock->empty() &&
"EmitDefaultStmt: Default block already defined?");
void CodeGenFunction::EmitSwitchStmt(const SwitchStmt &S) {
CleanupScope ConditionScope(*this);
if (S.getConditionVariable())
llvm::Value *CondV = EmitScalarExpr(S.getCond());
// Handle nested switch statements.
llvm::SwitchInst *SavedSwitchInsn = SwitchInsn;
llvm::BasicBlock *SavedCRBlock = CaseRangeBlock;
// Create basic block to hold stuff that comes after switch
// statement. We also need to create a default block now so that
// explicit case ranges tests can have a place to jump to on
// failure.
llvm::BasicBlock *NextBlock = createBasicBlock("sw.epilog");
llvm::BasicBlock *DefaultBlock = createBasicBlock("sw.default");
SwitchInsn = Builder.CreateSwitch(CondV, DefaultBlock);
CaseRangeBlock = DefaultBlock;
// Clear the insertion point to indicate we are in unreachable code.
// All break statements jump to NextBlock. If BreakContinueStack is non empty
// then reuse last ContinueBlock.
llvm::BasicBlock *ContinueBlock = 0;
if (!BreakContinueStack.empty())
ContinueBlock = BreakContinueStack.back().ContinueBlock;
// Ensure any vlas created between there and here, are undone
BreakContinueStack.push_back(BreakContinue(NextBlock, ContinueBlock));
// Emit switch body.
// Update the default block in case explicit case range tests have
// been chained on top.
SwitchInsn->setSuccessor(0, CaseRangeBlock);
// If a default was never emitted then reroute any jumps to it and
// discard.
if (!DefaultBlock->getParent()) {
delete DefaultBlock;
// Emit continuation.
EmitBlock(NextBlock, true);
SwitchInsn = SavedSwitchInsn;
CaseRangeBlock = SavedCRBlock;
static std::string
SimplifyConstraint(const char *Constraint, const TargetInfo &Target,
llvm::SmallVectorImpl<TargetInfo::ConstraintInfo> *OutCons=0) {
std::string Result;
while (*Constraint) {
switch (*Constraint) {
Result += Target.convertConstraint(*Constraint);
// Ignore these
case '*':
case '?':
case '!':
case 'g':
Result += "imr";
case '[': {
assert(OutCons &&
"Must pass output names to constraints with a symbolic name");
unsigned Index;
bool result = Target.resolveSymbolicName(Constraint,
OutCons->size(), Index);
assert(result && "Could not resolve symbolic name"); result=result;
Result += llvm::utostr(Index);
return Result;
llvm::Value* CodeGenFunction::EmitAsmInput(const AsmStmt &S,
const TargetInfo::ConstraintInfo &Info,
const Expr *InputExpr,
std::string &ConstraintStr) {
llvm::Value *Arg;
if (Info.allowsRegister() || !Info.allowsMemory()) {
if (!CodeGenFunction::hasAggregateLLVMType(InputExpr->getType())) {
Arg = EmitScalarExpr(InputExpr);
} else {
InputExpr = InputExpr->IgnoreParenNoopCasts(getContext());
LValue Dest = EmitLValue(InputExpr);
const llvm::Type *Ty = ConvertType(InputExpr->getType());
uint64_t Size = CGM.getTargetData().getTypeSizeInBits(Ty);
if (Size <= 64 && llvm::isPowerOf2_64(Size)) {
Ty = llvm::IntegerType::get(VMContext, Size);
Ty = llvm::PointerType::getUnqual(Ty);
Arg = Builder.CreateLoad(Builder.CreateBitCast(Dest.getAddress(), Ty));
} else {
Arg = Dest.getAddress();
ConstraintStr += '*';
} else {
InputExpr = InputExpr->IgnoreParenNoopCasts(getContext());
LValue Dest = EmitLValue(InputExpr);
Arg = Dest.getAddress();
ConstraintStr += '*';
return Arg;
void CodeGenFunction::EmitAsmStmt(const AsmStmt &S) {
// Analyze the asm string to decompose it into its pieces. We know that Sema
// has already done this, so it is guaranteed to be successful.
llvm::SmallVector<AsmStmt::AsmStringPiece, 4> Pieces;
unsigned DiagOffs;
S.AnalyzeAsmString(Pieces, getContext(), DiagOffs);
// Assemble the pieces into the final asm string.
std::string AsmString;
for (unsigned i = 0, e = Pieces.size(); i != e; ++i) {
if (Pieces[i].isString())
AsmString += Pieces[i].getString();
else if (Pieces[i].getModifier() == '\0')
AsmString += '$' + llvm::utostr(Pieces[i].getOperandNo());
AsmString += "${" + llvm::utostr(Pieces[i].getOperandNo()) + ':' +
Pieces[i].getModifier() + '}';
// Get all the output and input constraints together.
llvm::SmallVector<TargetInfo::ConstraintInfo, 4> OutputConstraintInfos;
llvm::SmallVector<TargetInfo::ConstraintInfo, 4> InputConstraintInfos;
for (unsigned i = 0, e = S.getNumOutputs(); i != e; i++) {
TargetInfo::ConstraintInfo Info(S.getOutputConstraint(i),
bool IsValid = Target.validateOutputConstraint(Info); (void)IsValid;
assert(IsValid && "Failed to parse output constraint");
for (unsigned i = 0, e = S.getNumInputs(); i != e; i++) {
TargetInfo::ConstraintInfo Info(S.getInputConstraint(i),
bool IsValid = Target.validateInputConstraint(,
S.getNumOutputs(), Info);
assert(IsValid && "Failed to parse input constraint"); (void)IsValid;
std::string Constraints;
std::vector<LValue> ResultRegDests;
std::vector<QualType> ResultRegQualTys;
std::vector<const llvm::Type *> ResultRegTypes;
std::vector<const llvm::Type *> ResultTruncRegTypes;
std::vector<const llvm::Type*> ArgTypes;
std::vector<llvm::Value*> Args;
// Keep track of inout constraints.
std::string InOutConstraints;
std::vector<llvm::Value*> InOutArgs;
std::vector<const llvm::Type*> InOutArgTypes;
for (unsigned i = 0, e = S.getNumOutputs(); i != e; i++) {
TargetInfo::ConstraintInfo &Info = OutputConstraintInfos[i];
// Simplify the output constraint.
std::string OutputConstraint(S.getOutputConstraint(i));
OutputConstraint = SimplifyConstraint(OutputConstraint.c_str() + 1, Target);
const Expr *OutExpr = S.getOutputExpr(i);
OutExpr = OutExpr->IgnoreParenNoopCasts(getContext());
LValue Dest = EmitLValue(OutExpr);
if (!Constraints.empty())
Constraints += ',';
// If this is a register output, then make the inline asm return it
// by-value. If this is a memory result, return the value by-reference.
if (!Info.allowsMemory() && !hasAggregateLLVMType(OutExpr->getType())) {
Constraints += "=" + OutputConstraint;
// If this output is tied to an input, and if the input is larger, then
// we need to set the actual result type of the inline asm node to be the
// same as the input type.
if (Info.hasMatchingInput()) {
unsigned InputNo;
for (InputNo = 0; InputNo != S.getNumInputs(); ++InputNo) {
TargetInfo::ConstraintInfo &Input = InputConstraintInfos[InputNo];
if (Input.hasTiedOperand() &&
Input.getTiedOperand() == i)
assert(InputNo != S.getNumInputs() && "Didn't find matching input!");
QualType InputTy = S.getInputExpr(InputNo)->getType();
QualType OutputTy = OutExpr->getType();
uint64_t InputSize = getContext().getTypeSize(InputTy);
if (getContext().getTypeSize(OutputTy) < InputSize) {
// Form the asm to return the value as a larger integer type.
ResultRegTypes.back() = llvm::IntegerType::get(VMContext, (unsigned)InputSize);
} else {
Constraints += "=*";
Constraints += OutputConstraint;
if (Info.isReadWrite()) {
InOutConstraints += ',';
const Expr *InputExpr = S.getOutputExpr(i);
llvm::Value *Arg = EmitAsmInput(S, Info, InputExpr, InOutConstraints);
if (Info.allowsRegister())
InOutConstraints += llvm::utostr(i);
InOutConstraints += OutputConstraint;
unsigned NumConstraints = S.getNumOutputs() + S.getNumInputs();
for (unsigned i = 0, e = S.getNumInputs(); i != e; i++) {
const Expr *InputExpr = S.getInputExpr(i);
TargetInfo::ConstraintInfo &Info = InputConstraintInfos[i];
if (!Constraints.empty())
Constraints += ',';
// Simplify the input constraint.
std::string InputConstraint(S.getInputConstraint(i));
InputConstraint = SimplifyConstraint(InputConstraint.c_str(), Target,
llvm::Value *Arg = EmitAsmInput(S, Info, InputExpr, Constraints);
// If this input argument is tied to a larger output result, extend the
// input to be the same size as the output. The LLVM backend wants to see
// the input and output of a matching constraint be the same size. Note
// that GCC does not define what the top bits are here. We use zext because
// that is usually cheaper, but LLVM IR should really get an anyext someday.
if (Info.hasTiedOperand()) {
unsigned Output = Info.getTiedOperand();
QualType OutputTy = S.getOutputExpr(Output)->getType();
QualType InputTy = InputExpr->getType();
if (getContext().getTypeSize(OutputTy) >
getContext().getTypeSize(InputTy)) {
// Use ptrtoint as appropriate so that we can do our extension.
if (isa<llvm::PointerType>(Arg->getType()))
Arg = Builder.CreatePtrToInt(Arg,
llvm::IntegerType::get(VMContext, LLVMPointerWidth));
unsigned OutputSize = (unsigned)getContext().getTypeSize(OutputTy);
Arg = Builder.CreateZExt(Arg, llvm::IntegerType::get(VMContext, OutputSize));
Constraints += InputConstraint;
// Append the "input" part of inout constraints last.
for (unsigned i = 0, e = InOutArgs.size(); i != e; i++) {
Constraints += InOutConstraints;
// Clobbers
for (unsigned i = 0, e = S.getNumClobbers(); i != e; i++) {
llvm::StringRef Clobber = S.getClobber(i)->getString();
Clobber = Target.getNormalizedGCCRegisterName(Clobber);
if (i != 0 || NumConstraints != 0)
Constraints += ',';
Constraints += "~{";
Constraints += Clobber;
Constraints += '}';
// Add machine specific clobbers
std::string MachineClobbers = Target.getClobbers();
if (!MachineClobbers.empty()) {
if (!Constraints.empty())
Constraints += ',';
Constraints += MachineClobbers;
const llvm::Type *ResultType;
if (ResultRegTypes.empty())
ResultType = llvm::Type::getVoidTy(VMContext);
else if (ResultRegTypes.size() == 1)
ResultType = ResultRegTypes[0];
ResultType = llvm::StructType::get(VMContext, ResultRegTypes);
const llvm::FunctionType *FTy =
llvm::FunctionType::get(ResultType, ArgTypes, false);
llvm::InlineAsm *IA =
llvm::InlineAsm::get(FTy, AsmString, Constraints,
S.isVolatile() || S.getNumOutputs() == 0);
llvm::CallInst *Result = Builder.CreateCall(IA, Args.begin(), Args.end());
Result->addAttribute(~0, llvm::Attribute::NoUnwind);
// Extract all of the register value results from the asm.
std::vector<llvm::Value*> RegResults;
if (ResultRegTypes.size() == 1) {
} else {
for (unsigned i = 0, e = ResultRegTypes.size(); i != e; ++i) {
llvm::Value *Tmp = Builder.CreateExtractValue(Result, i, "asmresult");
for (unsigned i = 0, e = RegResults.size(); i != e; ++i) {
llvm::Value *Tmp = RegResults[i];
// If the result type of the LLVM IR asm doesn't match the result type of
// the expression, do the conversion.
if (ResultRegTypes[i] != ResultTruncRegTypes[i]) {
const llvm::Type *TruncTy = ResultTruncRegTypes[i];
// Truncate the integer result to the right size, note that
// ResultTruncRegTypes can be a pointer.
uint64_t ResSize = CGM.getTargetData().getTypeSizeInBits(TruncTy);
Tmp = Builder.CreateTrunc(Tmp, llvm::IntegerType::get(VMContext, (unsigned)ResSize));
if (Tmp->getType() != TruncTy) {
Tmp = Builder.CreateIntToPtr(Tmp, TruncTy);
EmitStoreThroughLValue(RValue::get(Tmp), ResultRegDests[i],