1 //===- HexagonOptimizeSZextends.cpp - Remove unnecessary argument extends -===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Pass that removes sign extends for function parameters. These parameters
11 // are already sign extended by the caller per Hexagon's ABI
13 //===----------------------------------------------------------------------===//
15 #include "llvm/CodeGen/StackProtector.h"
16 #include "llvm/IR/Function.h"
17 #include "llvm/IR/Instructions.h"
18 #include "llvm/IR/IntrinsicInst.h"
19 #include "llvm/Pass.h"
20 #include "llvm/Transforms/Scalar.h"
27 FunctionPass *createHexagonOptimizeSZextends();
28 void initializeHexagonOptimizeSZextendsPass(PassRegistry&);
32 struct HexagonOptimizeSZextends : public FunctionPass {
35 HexagonOptimizeSZextends() : FunctionPass(ID) {
36 initializeHexagonOptimizeSZextendsPass(*PassRegistry::getPassRegistry());
38 bool runOnFunction(Function &F) override;
40 StringRef getPassName() const override { return "Remove sign extends"; }
42 void getAnalysisUsage(AnalysisUsage &AU) const override {
43 AU.addPreserved<StackProtector>();
44 FunctionPass::getAnalysisUsage(AU);
47 bool intrinsicAlreadySextended(Intrinsic::ID IntID);
51 char HexagonOptimizeSZextends::ID = 0;
53 INITIALIZE_PASS(HexagonOptimizeSZextends, "reargs",
54 "Remove Sign and Zero Extends for Args", false, false)
56 bool HexagonOptimizeSZextends::intrinsicAlreadySextended(Intrinsic::ID IntID) {
58 case llvm::Intrinsic::hexagon_A2_addh_l16_sat_ll:
66 bool HexagonOptimizeSZextends::runOnFunction(Function &F) {
71 // Try to optimize sign extends in formal parameters. It's relying on
72 // callee already sign extending the values. I'm not sure if our ABI
73 // requires callee to sign extend though.
74 for (auto &Arg : F.args()) {
75 if (F.getAttributes().hasAttribute(Idx, Attribute::SExt)) {
76 if (!isa<PointerType>(Arg.getType())) {
77 for (auto UI = Arg.use_begin(); UI != Arg.use_end();) {
78 if (isa<SExtInst>(*UI)) {
79 Instruction* Use = cast<Instruction>(*UI);
80 SExtInst* SI = new SExtInst(&Arg, Use->getType());
81 assert (EVT::getEVT(SI->getType()) ==
82 (EVT::getEVT(Use->getType())));
84 Use->replaceAllUsesWith(SI);
85 Instruction* First = &F.getEntryBlock().front();
86 SI->insertBefore(First);
87 Use->eraseFromParent();
97 // Try to remove redundant sext operations on Hexagon. The hardware
98 // already sign extends many 16 bit intrinsic operations to 32 bits.
100 // %34 = tail call i32 @llvm.hexagon.A2.addh.l16.sat.ll(i32 %x, i32 %y)
101 // %sext233 = shl i32 %34, 16
102 // %conv52 = ashr exact i32 %sext233, 16
105 // Look for arithmetic shift right by 16.
106 BinaryOperator *Ashr = dyn_cast<BinaryOperator>(&I);
107 if (!(Ashr && Ashr->getOpcode() == Instruction::AShr))
109 Value *AshrOp1 = Ashr->getOperand(1);
110 ConstantInt *C = dyn_cast<ConstantInt>(AshrOp1);
111 // Right shifted by 16.
112 if (!(C && C->getSExtValue() == 16))
115 // The first operand of Ashr comes from logical shift left.
116 Instruction *Shl = dyn_cast<Instruction>(Ashr->getOperand(0));
117 if (!(Shl && Shl->getOpcode() == Instruction::Shl))
119 Value *Intr = Shl->getOperand(0);
120 Value *ShlOp1 = Shl->getOperand(1);
121 C = dyn_cast<ConstantInt>(ShlOp1);
122 // Left shifted by 16.
123 if (!(C && C->getSExtValue() == 16))
126 // The first operand of Shl comes from an intrinsic.
127 if (IntrinsicInst *I = dyn_cast<IntrinsicInst>(Intr)) {
128 if (!intrinsicAlreadySextended(I->getIntrinsicID()))
130 // All is well. Replace all uses of AShr with I.
131 for (auto UI = Ashr->user_begin(), UE = Ashr->user_end();
133 const Use &TheUse = UI.getUse();
134 if (Instruction *J = dyn_cast<Instruction>(TheUse.getUser())) {
135 J->replaceUsesOfWith(Ashr, I);
146 FunctionPass *llvm::createHexagonOptimizeSZextends() {
147 return new HexagonOptimizeSZextends();