1 //===-- WebAssemblyPeephole.cpp - WebAssembly Peephole Optimiztions -------===//
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 //===----------------------------------------------------------------------===//
11 /// \brief Late peephole optimizations for WebAssembly.
13 //===----------------------------------------------------------------------===//
15 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
16 #include "WebAssembly.h"
17 #include "WebAssemblyMachineFunctionInfo.h"
18 #include "WebAssemblySubtarget.h"
19 #include "llvm/Analysis/TargetLibraryInfo.h"
20 #include "llvm/CodeGen/MachineFunctionPass.h"
21 #include "llvm/CodeGen/MachineInstrBuilder.h"
22 #include "llvm/CodeGen/MachineRegisterInfo.h"
25 #define DEBUG_TYPE "wasm-peephole"
27 static cl::opt<bool> DisableWebAssemblyFallthroughReturnOpt(
28 "disable-wasm-fallthrough-return-opt", cl::Hidden,
29 cl::desc("WebAssembly: Disable fallthrough-return optimizations."),
33 class WebAssemblyPeephole final : public MachineFunctionPass {
34 StringRef getPassName() const override {
35 return "WebAssembly late peephole optimizer";
38 void getAnalysisUsage(AnalysisUsage &AU) const override {
40 AU.addRequired<TargetLibraryInfoWrapperPass>();
41 MachineFunctionPass::getAnalysisUsage(AU);
44 bool runOnMachineFunction(MachineFunction &MF) override;
48 WebAssemblyPeephole() : MachineFunctionPass(ID) {}
50 } // end anonymous namespace
52 char WebAssemblyPeephole::ID = 0;
53 FunctionPass *llvm::createWebAssemblyPeephole() {
54 return new WebAssemblyPeephole();
57 /// If desirable, rewrite NewReg to a drop register.
58 static bool MaybeRewriteToDrop(unsigned OldReg, unsigned NewReg,
59 MachineOperand &MO, WebAssemblyFunctionInfo &MFI,
60 MachineRegisterInfo &MRI) {
62 if (OldReg == NewReg) {
64 unsigned NewReg = MRI.createVirtualRegister(MRI.getRegClass(OldReg));
67 MFI.stackifyVReg(NewReg);
72 static bool MaybeRewriteToFallthrough(MachineInstr &MI, MachineBasicBlock &MBB,
73 const MachineFunction &MF,
74 WebAssemblyFunctionInfo &MFI,
75 MachineRegisterInfo &MRI,
76 const WebAssemblyInstrInfo &TII,
77 unsigned FallthroughOpc,
78 unsigned CopyLocalOpc) {
79 if (DisableWebAssemblyFallthroughReturnOpt)
81 if (&MBB != &MF.back())
83 if (MF.getSubtarget<WebAssemblySubtarget>()
84 .getTargetTriple().isOSBinFormatELF()) {
85 if (&MI != &MBB.back())
88 MachineBasicBlock::iterator End = MBB.end();
90 assert(End->getOpcode() == WebAssembly::END_FUNCTION);
96 if (FallthroughOpc != WebAssembly::FALLTHROUGH_RETURN_VOID) {
97 // If the operand isn't stackified, insert a COPY to read the operand and
99 MachineOperand &MO = MI.getOperand(0);
100 unsigned Reg = MO.getReg();
101 if (!MFI.isVRegStackified(Reg)) {
102 unsigned NewReg = MRI.createVirtualRegister(MRI.getRegClass(Reg));
103 BuildMI(MBB, MI, MI.getDebugLoc(), TII.get(CopyLocalOpc), NewReg)
106 MFI.stackifyVReg(NewReg);
110 // Rewrite the return.
111 MI.setDesc(TII.get(FallthroughOpc));
115 bool WebAssemblyPeephole::runOnMachineFunction(MachineFunction &MF) {
117 dbgs() << "********** Peephole **********\n"
118 << "********** Function: " << MF.getName() << '\n';
121 MachineRegisterInfo &MRI = MF.getRegInfo();
122 WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
123 const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
124 const WebAssemblyTargetLowering &TLI =
125 *MF.getSubtarget<WebAssemblySubtarget>().getTargetLowering();
126 auto &LibInfo = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
127 bool Changed = false;
131 switch (MI.getOpcode()) {
134 case WebAssembly::CALL_I32:
135 case WebAssembly::CALL_I64: {
136 MachineOperand &Op1 = MI.getOperand(1);
137 if (Op1.isSymbol()) {
138 StringRef Name(Op1.getSymbolName());
139 if (Name == TLI.getLibcallName(RTLIB::MEMCPY) ||
140 Name == TLI.getLibcallName(RTLIB::MEMMOVE) ||
141 Name == TLI.getLibcallName(RTLIB::MEMSET)) {
143 if (LibInfo.getLibFunc(Name, Func)) {
144 const auto &Op2 = MI.getOperand(2);
146 report_fatal_error("Peephole: call to builtin function with "
147 "wrong signature, not consuming reg");
148 MachineOperand &MO = MI.getOperand(0);
149 unsigned OldReg = MO.getReg();
150 unsigned NewReg = Op2.getReg();
152 if (MRI.getRegClass(NewReg) != MRI.getRegClass(OldReg))
153 report_fatal_error("Peephole: call to builtin function with "
154 "wrong signature, from/to mismatch");
155 Changed |= MaybeRewriteToDrop(OldReg, NewReg, MO, MFI, MRI);
161 // Optimize away an explicit void return at the end of the function.
162 case WebAssembly::RETURN_I32:
163 Changed |= MaybeRewriteToFallthrough(
164 MI, MBB, MF, MFI, MRI, TII, WebAssembly::FALLTHROUGH_RETURN_I32,
165 WebAssembly::COPY_I32);
167 case WebAssembly::RETURN_I64:
168 Changed |= MaybeRewriteToFallthrough(
169 MI, MBB, MF, MFI, MRI, TII, WebAssembly::FALLTHROUGH_RETURN_I64,
170 WebAssembly::COPY_I64);
172 case WebAssembly::RETURN_F32:
173 Changed |= MaybeRewriteToFallthrough(
174 MI, MBB, MF, MFI, MRI, TII, WebAssembly::FALLTHROUGH_RETURN_F32,
175 WebAssembly::COPY_F32);
177 case WebAssembly::RETURN_F64:
178 Changed |= MaybeRewriteToFallthrough(
179 MI, MBB, MF, MFI, MRI, TII, WebAssembly::FALLTHROUGH_RETURN_F64,
180 WebAssembly::COPY_F64);
182 case WebAssembly::RETURN_v16i8:
183 Changed |= MaybeRewriteToFallthrough(
184 MI, MBB, MF, MFI, MRI, TII, WebAssembly::FALLTHROUGH_RETURN_v16i8,
185 WebAssembly::COPY_V128);
187 case WebAssembly::RETURN_v8i16:
188 Changed |= MaybeRewriteToFallthrough(
189 MI, MBB, MF, MFI, MRI, TII, WebAssembly::FALLTHROUGH_RETURN_v8i16,
190 WebAssembly::COPY_V128);
192 case WebAssembly::RETURN_v4i32:
193 Changed |= MaybeRewriteToFallthrough(
194 MI, MBB, MF, MFI, MRI, TII, WebAssembly::FALLTHROUGH_RETURN_v4i32,
195 WebAssembly::COPY_V128);
197 case WebAssembly::RETURN_v4f32:
198 Changed |= MaybeRewriteToFallthrough(
199 MI, MBB, MF, MFI, MRI, TII, WebAssembly::FALLTHROUGH_RETURN_v4f32,
200 WebAssembly::COPY_V128);
202 case WebAssembly::RETURN_VOID:
203 Changed |= MaybeRewriteToFallthrough(
204 MI, MBB, MF, MFI, MRI, TII, WebAssembly::FALLTHROUGH_RETURN_VOID,
205 WebAssembly::INSTRUCTION_LIST_END);