113 lines
3.4 KiB
C++
113 lines
3.4 KiB
C++
//===--- ExpandLargeDivRem.cpp - Expand large div/rem ---------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass expands div/rem instructions with a bitwidth above a threshold
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// into a call to auto-generated functions.
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// This is useful for targets like x86_64 that cannot lower divisions
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// with more than 128 bits or targets like x86_32 that cannot lower divisions
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// with more than 64 bits.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/ExpandLargeDivRem.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/StringExtras.h"
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#include "llvm/Analysis/GlobalsModRef.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/InstIterator.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/InitializePasses.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Transforms/Utils/IntegerDivision.h"
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using namespace llvm;
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static cl::opt<unsigned>
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ExpandDivRemBits("expand-div-rem-bits", cl::Hidden, cl::init(128),
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cl::desc("div and rem instructions on integers with "
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"more than <N> bits are expanded."));
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static bool runImpl(Function &F) {
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SmallVector<BinaryOperator *, 4> Replace;
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bool Modified = false;
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for (auto &I : instructions(F)) {
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switch (I.getOpcode()) {
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case Instruction::UDiv:
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case Instruction::SDiv:
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case Instruction::URem:
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case Instruction::SRem: {
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// TODO: This doesn't handle vectors.
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auto *IntTy = dyn_cast<IntegerType>(I.getType());
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if (!IntTy || IntTy->getIntegerBitWidth() <= ExpandDivRemBits)
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continue;
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Replace.push_back(&cast<BinaryOperator>(I));
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Modified = true;
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break;
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}
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default:
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break;
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}
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}
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if (Replace.empty())
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return false;
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while (!Replace.empty()) {
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BinaryOperator *I = Replace.pop_back_val();
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if (I->getOpcode() == Instruction::UDiv ||
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I->getOpcode() == Instruction::SDiv) {
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expandDivision(I);
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} else {
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expandRemainder(I);
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}
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}
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return Modified;
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}
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PreservedAnalyses ExpandLargeDivRemPass::run(Function &F,
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FunctionAnalysisManager &AM) {
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bool Changed = runImpl(F);
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if (Changed)
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return PreservedAnalyses::none();
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return PreservedAnalyses::all();
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}
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class ExpandLargeDivRemLegacyPass : public FunctionPass {
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public:
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static char ID;
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ExpandLargeDivRemLegacyPass() : FunctionPass(ID) {
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initializeExpandLargeDivRemLegacyPassPass(*PassRegistry::getPassRegistry());
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}
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bool runOnFunction(Function &F) override { return runImpl(F); }
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.addPreserved<AAResultsWrapperPass>();
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AU.addPreserved<GlobalsAAWrapperPass>();
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}
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};
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char ExpandLargeDivRemLegacyPass::ID = 0;
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INITIALIZE_PASS_BEGIN(ExpandLargeDivRemLegacyPass, "expand-large-div-rem",
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"Expand large div/rem", false, false)
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INITIALIZE_PASS_END(ExpandLargeDivRemLegacyPass, "expand-large-div-rem",
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"Expand large div/rem", false, false)
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FunctionPass *llvm::createExpandLargeDivRemPass() {
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return new ExpandLargeDivRemLegacyPass();
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}
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