diff options
Diffstat (limited to 'lib/Target/WebAssembly/WebAssemblyPeephole.cpp')
| -rw-r--r-- | lib/Target/WebAssembly/WebAssemblyPeephole.cpp | 135 |
1 files changed, 123 insertions, 12 deletions
diff --git a/lib/Target/WebAssembly/WebAssemblyPeephole.cpp b/lib/Target/WebAssembly/WebAssemblyPeephole.cpp index 4ad6eed7385b..56d44e6466eb 100644 --- a/lib/Target/WebAssembly/WebAssemblyPeephole.cpp +++ b/lib/Target/WebAssembly/WebAssemblyPeephole.cpp @@ -12,14 +12,23 @@ /// //===----------------------------------------------------------------------===// -#include "WebAssembly.h" #include "MCTargetDesc/WebAssemblyMCTargetDesc.h" +#include "WebAssembly.h" #include "WebAssemblyMachineFunctionInfo.h" +#include "WebAssemblySubtarget.h" +#include "llvm/Analysis/TargetLibraryInfo.h" #include "llvm/CodeGen/MachineFunctionPass.h" +#include "llvm/CodeGen/MachineInstrBuilder.h" +#include "llvm/CodeGen/MachineRegisterInfo.h" using namespace llvm; #define DEBUG_TYPE "wasm-peephole" +static cl::opt<bool> DisableWebAssemblyFallthroughReturnOpt( + "disable-wasm-fallthrough-return-opt", cl::Hidden, + cl::desc("WebAssembly: Disable fallthrough-return optimizations."), + cl::init(false)); + namespace { class WebAssemblyPeephole final : public MachineFunctionPass { const char *getPassName() const override { @@ -28,6 +37,7 @@ class WebAssemblyPeephole final : public MachineFunctionPass { void getAnalysisUsage(AnalysisUsage &AU) const override { AU.setPreservesCFG(); + AU.addRequired<TargetLibraryInfoWrapperPass>(); MachineFunctionPass::getAnalysisUsage(AU); } @@ -44,11 +54,65 @@ FunctionPass *llvm::createWebAssemblyPeephole() { return new WebAssemblyPeephole(); } -bool WebAssemblyPeephole::runOnMachineFunction(MachineFunction &MF) { +/// If desirable, rewrite NewReg to a drop register. +static bool MaybeRewriteToDrop(unsigned OldReg, unsigned NewReg, + MachineOperand &MO, WebAssemblyFunctionInfo &MFI, + MachineRegisterInfo &MRI) { bool Changed = false; + if (OldReg == NewReg) { + Changed = true; + unsigned NewReg = MRI.createVirtualRegister(MRI.getRegClass(OldReg)); + MO.setReg(NewReg); + MO.setIsDead(); + MFI.stackifyVReg(NewReg); + } + return Changed; +} + +static bool MaybeRewriteToFallthrough(MachineInstr &MI, MachineBasicBlock &MBB, + const MachineFunction &MF, + WebAssemblyFunctionInfo &MFI, + MachineRegisterInfo &MRI, + const WebAssemblyInstrInfo &TII, + unsigned FallthroughOpc, + unsigned CopyLocalOpc) { + if (DisableWebAssemblyFallthroughReturnOpt) + return false; + if (&MBB != &MF.back()) + return false; + if (&MI != &MBB.back()) + return false; + + // If the operand isn't stackified, insert a COPY_LOCAL to read the operand + // and stackify it. + MachineOperand &MO = MI.getOperand(0); + unsigned Reg = MO.getReg(); + if (!MFI.isVRegStackified(Reg)) { + unsigned NewReg = MRI.createVirtualRegister(MRI.getRegClass(Reg)); + BuildMI(MBB, MI, MI.getDebugLoc(), TII.get(CopyLocalOpc), NewReg) + .addReg(Reg); + MO.setReg(NewReg); + MFI.stackifyVReg(NewReg); + } + + // Rewrite the return. + MI.setDesc(TII.get(FallthroughOpc)); + return true; +} + +bool WebAssemblyPeephole::runOnMachineFunction(MachineFunction &MF) { + DEBUG({ + dbgs() << "********** Peephole **********\n" + << "********** Function: " << MF.getName() << '\n'; + }); MachineRegisterInfo &MRI = MF.getRegInfo(); WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>(); + const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo(); + const WebAssemblyTargetLowering &TLI = + *MF.getSubtarget<WebAssemblySubtarget>().getTargetLowering(); + auto &LibInfo = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(); + bool Changed = false; for (auto &MBB : MF) for (auto &MI : MBB) @@ -66,20 +130,67 @@ bool WebAssemblyPeephole::runOnMachineFunction(MachineFunction &MF) { case WebAssembly::STORE_I64: { // Store instructions return their value operand. If we ended up using // the same register for both, replace it with a dead def so that it - // can use $discard instead. + // can use $drop instead. MachineOperand &MO = MI.getOperand(0); unsigned OldReg = MO.getReg(); - // TODO: Handle SP/physregs - if (OldReg == MI.getOperand(3).getReg() - && TargetRegisterInfo::isVirtualRegister(MI.getOperand(3).getReg())) { - Changed = true; - unsigned NewReg = MRI.createVirtualRegister(MRI.getRegClass(OldReg)); - MO.setReg(NewReg); - MO.setIsDead(); - MFI.stackifyVReg(NewReg); - MFI.addWAReg(NewReg, WebAssemblyFunctionInfo::UnusedReg); + unsigned NewReg = + MI.getOperand(WebAssembly::StoreValueOperandNo).getReg(); + Changed |= MaybeRewriteToDrop(OldReg, NewReg, MO, MFI, MRI); + break; + } + case WebAssembly::CALL_I32: + case WebAssembly::CALL_I64: { + MachineOperand &Op1 = MI.getOperand(1); + if (Op1.isSymbol()) { + StringRef Name(Op1.getSymbolName()); + if (Name == TLI.getLibcallName(RTLIB::MEMCPY) || + Name == TLI.getLibcallName(RTLIB::MEMMOVE) || + Name == TLI.getLibcallName(RTLIB::MEMSET)) { + LibFunc::Func Func; + if (LibInfo.getLibFunc(Name, Func)) { + const auto &Op2 = MI.getOperand(2); + if (!Op2.isReg()) + report_fatal_error("Peephole: call to builtin function with " + "wrong signature, not consuming reg"); + MachineOperand &MO = MI.getOperand(0); + unsigned OldReg = MO.getReg(); + unsigned NewReg = Op2.getReg(); + + if (MRI.getRegClass(NewReg) != MRI.getRegClass(OldReg)) + report_fatal_error("Peephole: call to builtin function with " + "wrong signature, from/to mismatch"); + Changed |= MaybeRewriteToDrop(OldReg, NewReg, MO, MFI, MRI); + } + } } + break; } + // Optimize away an explicit void return at the end of the function. + case WebAssembly::RETURN_I32: + Changed |= MaybeRewriteToFallthrough( + MI, MBB, MF, MFI, MRI, TII, WebAssembly::FALLTHROUGH_RETURN_I32, + WebAssembly::COPY_LOCAL_I32); + break; + case WebAssembly::RETURN_I64: + Changed |= MaybeRewriteToFallthrough( + MI, MBB, MF, MFI, MRI, TII, WebAssembly::FALLTHROUGH_RETURN_I64, + WebAssembly::COPY_LOCAL_I64); + break; + case WebAssembly::RETURN_F32: + Changed |= MaybeRewriteToFallthrough( + MI, MBB, MF, MFI, MRI, TII, WebAssembly::FALLTHROUGH_RETURN_F32, + WebAssembly::COPY_LOCAL_F32); + break; + case WebAssembly::RETURN_F64: + Changed |= MaybeRewriteToFallthrough( + MI, MBB, MF, MFI, MRI, TII, WebAssembly::FALLTHROUGH_RETURN_F64, + WebAssembly::COPY_LOCAL_F64); + break; + case WebAssembly::RETURN_VOID: + if (!DisableWebAssemblyFallthroughReturnOpt && + &MBB == &MF.back() && &MI == &MBB.back()) + MI.setDesc(TII.get(WebAssembly::FALLTHROUGH_RETURN_VOID)); + break; } return Changed; |