| //===- HexagonOptimizeSZextends.cpp - Remove unnecessary argument extends -===// |
| // |
| // 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 |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // Pass that removes sign extends for function parameters. These parameters |
| // are already sign extended by the caller per Hexagon's ABI |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/CodeGen/StackProtector.h" |
| #include "llvm/IR/Function.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/IntrinsicInst.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Transforms/Scalar.h" |
| |
| #include "Hexagon.h" |
| |
| using namespace llvm; |
| |
| namespace llvm { |
| FunctionPass *createHexagonOptimizeSZextends(); |
| void initializeHexagonOptimizeSZextendsPass(PassRegistry&); |
| } |
| |
| namespace { |
| struct HexagonOptimizeSZextends : public FunctionPass { |
| public: |
| static char ID; |
| HexagonOptimizeSZextends() : FunctionPass(ID) { |
| initializeHexagonOptimizeSZextendsPass(*PassRegistry::getPassRegistry()); |
| } |
| bool runOnFunction(Function &F) override; |
| |
| StringRef getPassName() const override { return "Remove sign extends"; } |
| |
| void getAnalysisUsage(AnalysisUsage &AU) const override { |
| AU.addPreserved<StackProtector>(); |
| FunctionPass::getAnalysisUsage(AU); |
| } |
| |
| bool intrinsicAlreadySextended(Intrinsic::ID IntID); |
| }; |
| } |
| |
| char HexagonOptimizeSZextends::ID = 0; |
| |
| INITIALIZE_PASS(HexagonOptimizeSZextends, "reargs", |
| "Remove Sign and Zero Extends for Args", false, false) |
| |
| bool HexagonOptimizeSZextends::intrinsicAlreadySextended(Intrinsic::ID IntID) { |
| switch(IntID) { |
| case llvm::Intrinsic::hexagon_A2_addh_l16_sat_ll: |
| return true; |
| default: |
| break; |
| } |
| return false; |
| } |
| |
| bool HexagonOptimizeSZextends::runOnFunction(Function &F) { |
| if (skipFunction(F)) |
| return false; |
| |
| unsigned Idx = 1; |
| // Try to optimize sign extends in formal parameters. It's relying on |
| // callee already sign extending the values. I'm not sure if our ABI |
| // requires callee to sign extend though. |
| for (auto &Arg : F.args()) { |
| if (F.getAttributes().hasAttribute(Idx, Attribute::SExt)) { |
| if (!isa<PointerType>(Arg.getType())) { |
| for (auto UI = Arg.use_begin(); UI != Arg.use_end();) { |
| if (isa<SExtInst>(*UI)) { |
| Instruction* Use = cast<Instruction>(*UI); |
| SExtInst* SI = new SExtInst(&Arg, Use->getType()); |
| assert (EVT::getEVT(SI->getType()) == |
| (EVT::getEVT(Use->getType()))); |
| ++UI; |
| Use->replaceAllUsesWith(SI); |
| Instruction* First = &F.getEntryBlock().front(); |
| SI->insertBefore(First); |
| Use->eraseFromParent(); |
| } else { |
| ++UI; |
| } |
| } |
| } |
| } |
| ++Idx; |
| } |
| |
| // Try to remove redundant sext operations on Hexagon. The hardware |
| // already sign extends many 16 bit intrinsic operations to 32 bits. |
| // For example: |
| // %34 = tail call i32 @llvm.hexagon.A2.addh.l16.sat.ll(i32 %x, i32 %y) |
| // %sext233 = shl i32 %34, 16 |
| // %conv52 = ashr exact i32 %sext233, 16 |
| for (auto &B : F) { |
| for (auto &I : B) { |
| // Look for arithmetic shift right by 16. |
| BinaryOperator *Ashr = dyn_cast<BinaryOperator>(&I); |
| if (!(Ashr && Ashr->getOpcode() == Instruction::AShr)) |
| continue; |
| Value *AshrOp1 = Ashr->getOperand(1); |
| ConstantInt *C = dyn_cast<ConstantInt>(AshrOp1); |
| // Right shifted by 16. |
| if (!(C && C->getSExtValue() == 16)) |
| continue; |
| |
| // The first operand of Ashr comes from logical shift left. |
| Instruction *Shl = dyn_cast<Instruction>(Ashr->getOperand(0)); |
| if (!(Shl && Shl->getOpcode() == Instruction::Shl)) |
| continue; |
| Value *Intr = Shl->getOperand(0); |
| Value *ShlOp1 = Shl->getOperand(1); |
| C = dyn_cast<ConstantInt>(ShlOp1); |
| // Left shifted by 16. |
| if (!(C && C->getSExtValue() == 16)) |
| continue; |
| |
| // The first operand of Shl comes from an intrinsic. |
| if (IntrinsicInst *I = dyn_cast<IntrinsicInst>(Intr)) { |
| if (!intrinsicAlreadySextended(I->getIntrinsicID())) |
| continue; |
| // All is well. Replace all uses of AShr with I. |
| for (auto UI = Ashr->user_begin(), UE = Ashr->user_end(); |
| UI != UE; ++UI) { |
| const Use &TheUse = UI.getUse(); |
| if (Instruction *J = dyn_cast<Instruction>(TheUse.getUser())) { |
| J->replaceUsesOfWith(Ashr, I); |
| } |
| } |
| } |
| } |
| } |
| |
| return true; |
| } |
| |
| |
| FunctionPass *llvm::createHexagonOptimizeSZextends() { |
| return new HexagonOptimizeSZextends(); |
| } |