| //===--- ExpandLargeDivRem.cpp - Expand large div/rem ---------------------===// |
| // |
| // 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 pass expands div/rem instructions with a bitwidth above a threshold |
| // into a call to auto-generated functions. |
| // This is useful for targets like x86_64 that cannot lower divisions |
| // with more than 128 bits or targets like x86_32 that cannot lower divisions |
| // with more than 64 bits. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/StringExtras.h" |
| #include "llvm/Analysis/GlobalsModRef.h" |
| #include "llvm/CodeGen/Passes.h" |
| #include "llvm/CodeGen/TargetLowering.h" |
| #include "llvm/CodeGen/TargetPassConfig.h" |
| #include "llvm/CodeGen/TargetSubtargetInfo.h" |
| #include "llvm/IR/IRBuilder.h" |
| #include "llvm/IR/InstIterator.h" |
| #include "llvm/IR/PassManager.h" |
| #include "llvm/InitializePasses.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Target/TargetMachine.h" |
| #include "llvm/Transforms/Utils/IntegerDivision.h" |
| |
| using namespace llvm; |
| |
| static cl::opt<unsigned> |
| ExpandDivRemBits("expand-div-rem-bits", cl::Hidden, |
| cl::init(llvm::IntegerType::MAX_INT_BITS), |
| cl::desc("div and rem instructions on integers with " |
| "more than <N> bits are expanded.")); |
| |
| static bool isConstantPowerOfTwo(llvm::Value *V, bool SignedOp) { |
| auto *C = dyn_cast<ConstantInt>(V); |
| if (!C) |
| return false; |
| |
| APInt Val = C->getValue(); |
| if (SignedOp && Val.isNegative()) |
| Val = -Val; |
| return Val.isPowerOf2(); |
| } |
| |
| static bool isSigned(unsigned int Opcode) { |
| return Opcode == Instruction::SDiv || Opcode == Instruction::SRem; |
| } |
| |
| static bool runImpl(Function &F, const TargetLowering &TLI) { |
| SmallVector<BinaryOperator *, 4> Replace; |
| bool Modified = false; |
| |
| unsigned MaxLegalDivRemBitWidth = TLI.getMaxDivRemBitWidthSupported(); |
| if (ExpandDivRemBits != llvm::IntegerType::MAX_INT_BITS) |
| MaxLegalDivRemBitWidth = ExpandDivRemBits; |
| |
| if (MaxLegalDivRemBitWidth >= llvm::IntegerType::MAX_INT_BITS) |
| return false; |
| |
| for (auto &I : instructions(F)) { |
| switch (I.getOpcode()) { |
| case Instruction::UDiv: |
| case Instruction::SDiv: |
| case Instruction::URem: |
| case Instruction::SRem: { |
| // TODO: This doesn't handle vectors. |
| auto *IntTy = dyn_cast<IntegerType>(I.getType()); |
| if (!IntTy || IntTy->getIntegerBitWidth() <= MaxLegalDivRemBitWidth) |
| continue; |
| |
| // The backend has peephole optimizations for powers of two. |
| if (isConstantPowerOfTwo(I.getOperand(1), isSigned(I.getOpcode()))) |
| continue; |
| |
| Replace.push_back(&cast<BinaryOperator>(I)); |
| Modified = true; |
| break; |
| } |
| default: |
| break; |
| } |
| } |
| |
| if (Replace.empty()) |
| return false; |
| |
| while (!Replace.empty()) { |
| BinaryOperator *I = Replace.pop_back_val(); |
| |
| if (I->getOpcode() == Instruction::UDiv || |
| I->getOpcode() == Instruction::SDiv) { |
| expandDivision(I); |
| } else { |
| expandRemainder(I); |
| } |
| } |
| |
| return Modified; |
| } |
| |
| namespace { |
| class ExpandLargeDivRemLegacyPass : public FunctionPass { |
| public: |
| static char ID; |
| |
| ExpandLargeDivRemLegacyPass() : FunctionPass(ID) { |
| initializeExpandLargeDivRemLegacyPassPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| bool runOnFunction(Function &F) override { |
| auto *TM = &getAnalysis<TargetPassConfig>().getTM<TargetMachine>(); |
| auto *TLI = TM->getSubtargetImpl(F)->getTargetLowering(); |
| return runImpl(F, *TLI); |
| } |
| |
| void getAnalysisUsage(AnalysisUsage &AU) const override { |
| AU.addRequired<TargetPassConfig>(); |
| AU.addPreserved<AAResultsWrapperPass>(); |
| AU.addPreserved<GlobalsAAWrapperPass>(); |
| } |
| }; |
| } // namespace |
| |
| char ExpandLargeDivRemLegacyPass::ID = 0; |
| INITIALIZE_PASS_BEGIN(ExpandLargeDivRemLegacyPass, "expand-large-div-rem", |
| "Expand large div/rem", false, false) |
| INITIALIZE_PASS_END(ExpandLargeDivRemLegacyPass, "expand-large-div-rem", |
| "Expand large div/rem", false, false) |
| |
| FunctionPass *llvm::createExpandLargeDivRemPass() { |
| return new ExpandLargeDivRemLegacyPass(); |
| } |