| //===-- WebAssemblyReplacePhysRegs.cpp - Replace phys regs with virt regs -===// |
| // |
| // 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 |
| // |
| //===----------------------------------------------------------------------===// |
| /// |
| /// \file |
| /// This file implements a pass that replaces physical registers with |
| /// virtual registers. |
| /// |
| /// LLVM expects certain physical registers, such as a stack pointer. However, |
| /// WebAssembly doesn't actually have such physical registers. This pass is run |
| /// once LLVM no longer needs these registers, and replaces them with virtual |
| /// registers, so they can participate in register stackifying and coloring in |
| /// the normal way. |
| /// |
| //===----------------------------------------------------------------------===// |
| |
| #include "MCTargetDesc/WebAssemblyMCTargetDesc.h" |
| #include "WebAssembly.h" |
| #include "WebAssemblyMachineFunctionInfo.h" |
| #include "WebAssemblySubtarget.h" |
| #include "llvm/CodeGen/MachineFunctionPass.h" |
| #include "llvm/CodeGen/MachineRegisterInfo.h" |
| #include "llvm/CodeGen/Passes.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/raw_ostream.h" |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "wasm-replace-phys-regs" |
| |
| namespace { |
| class WebAssemblyReplacePhysRegs final : public MachineFunctionPass { |
| public: |
| static char ID; // Pass identification, replacement for typeid |
| WebAssemblyReplacePhysRegs() : MachineFunctionPass(ID) {} |
| |
| private: |
| StringRef getPassName() const override { |
| return "WebAssembly Replace Physical Registers"; |
| } |
| |
| void getAnalysisUsage(AnalysisUsage &AU) const override { |
| AU.setPreservesCFG(); |
| MachineFunctionPass::getAnalysisUsage(AU); |
| } |
| |
| bool runOnMachineFunction(MachineFunction &MF) override; |
| }; |
| } // end anonymous namespace |
| |
| char WebAssemblyReplacePhysRegs::ID = 0; |
| INITIALIZE_PASS(WebAssemblyReplacePhysRegs, DEBUG_TYPE, |
| "Replace physical registers with virtual registers", false, |
| false) |
| |
| FunctionPass *llvm::createWebAssemblyReplacePhysRegs() { |
| return new WebAssemblyReplacePhysRegs(); |
| } |
| |
| bool WebAssemblyReplacePhysRegs::runOnMachineFunction(MachineFunction &MF) { |
| LLVM_DEBUG({ |
| dbgs() << "********** Replace Physical Registers **********\n" |
| << "********** Function: " << MF.getName() << '\n'; |
| }); |
| |
| MachineRegisterInfo &MRI = MF.getRegInfo(); |
| auto &TRI = *MF.getSubtarget<WebAssemblySubtarget>().getRegisterInfo(); |
| bool Changed = false; |
| |
| assert(!mustPreserveAnalysisID(LiveIntervalsID) && |
| "LiveIntervals shouldn't be active yet!"); |
| // We don't preserve SSA or liveness. |
| MRI.leaveSSA(); |
| MRI.invalidateLiveness(); |
| |
| for (unsigned PReg = WebAssembly::NoRegister + 1; |
| PReg < WebAssembly::NUM_TARGET_REGS; ++PReg) { |
| // Skip fake registers that are never used explicitly. |
| if (PReg == WebAssembly::VALUE_STACK || PReg == WebAssembly::ARGUMENTS) |
| continue; |
| |
| // Replace explicit uses of the physical register with a virtual register. |
| const TargetRegisterClass *RC = TRI.getMinimalPhysRegClass(PReg); |
| unsigned VReg = WebAssembly::NoRegister; |
| for (MachineOperand &MO : |
| llvm::make_early_inc_range(MRI.reg_operands(PReg))) { |
| if (!MO.isImplicit()) { |
| if (VReg == WebAssembly::NoRegister) { |
| VReg = MRI.createVirtualRegister(RC); |
| if (PReg == TRI.getFrameRegister(MF)) { |
| auto FI = MF.getInfo<WebAssemblyFunctionInfo>(); |
| assert(!FI->isFrameBaseVirtual()); |
| FI->setFrameBaseVreg(VReg); |
| LLVM_DEBUG({ |
| dbgs() << "replacing preg " << PReg << " with " << VReg << " (" |
| << Register::virtReg2Index(VReg) << ")\n"; |
| }); |
| } |
| } |
| MO.setReg(VReg); |
| Changed = true; |
| } |
| } |
| } |
| |
| return Changed; |
| } |