forked from OSchip/llvm-project
309 lines
11 KiB
C++
309 lines
11 KiB
C++
//===-- WebAssemblyExplicitLocals.cpp - Make Locals Explicit --------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// \brief This file converts any remaining registers into WebAssembly locals.
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///
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/// After register stackification and register coloring, convert non-stackified
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/// registers into locals, inserting explicit get_local and set_local
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/// instructions.
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///
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//===----------------------------------------------------------------------===//
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#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
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#include "WebAssembly.h"
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#include "WebAssemblyMachineFunctionInfo.h"
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#include "WebAssemblySubtarget.h"
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#include "WebAssemblyUtilities.h"
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#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
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#include "llvm/CodeGen/MachineInstrBuilder.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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#define DEBUG_TYPE "wasm-explicit-locals"
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namespace {
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class WebAssemblyExplicitLocals final : public MachineFunctionPass {
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StringRef getPassName() const override {
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return "WebAssembly Explicit Locals";
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}
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.setPreservesCFG();
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AU.addPreserved<MachineBlockFrequencyInfo>();
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MachineFunctionPass::getAnalysisUsage(AU);
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}
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bool runOnMachineFunction(MachineFunction &MF) override;
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public:
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static char ID; // Pass identification, replacement for typeid
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WebAssemblyExplicitLocals() : MachineFunctionPass(ID) {}
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};
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} // end anonymous namespace
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char WebAssemblyExplicitLocals::ID = 0;
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FunctionPass *llvm::createWebAssemblyExplicitLocals() {
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return new WebAssemblyExplicitLocals();
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}
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/// Return a local id number for the given register, assigning it a new one
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/// if it doesn't yet have one.
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static unsigned getLocalId(DenseMap<unsigned, unsigned> &Reg2Local,
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unsigned &CurLocal, unsigned Reg) {
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return Reg2Local.insert(std::make_pair(Reg, CurLocal++)).first->second;
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}
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/// Get the appropriate get_local opcode for the given register class.
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static unsigned getGetLocalOpcode(const TargetRegisterClass *RC) {
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if (RC == &WebAssembly::I32RegClass)
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return WebAssembly::GET_LOCAL_I32;
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if (RC == &WebAssembly::I64RegClass)
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return WebAssembly::GET_LOCAL_I64;
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if (RC == &WebAssembly::F32RegClass)
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return WebAssembly::GET_LOCAL_F32;
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if (RC == &WebAssembly::F64RegClass)
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return WebAssembly::GET_LOCAL_F64;
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if (RC == &WebAssembly::V128RegClass)
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return WebAssembly::GET_LOCAL_V128;
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llvm_unreachable("Unexpected register class");
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}
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/// Get the appropriate set_local opcode for the given register class.
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static unsigned getSetLocalOpcode(const TargetRegisterClass *RC) {
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if (RC == &WebAssembly::I32RegClass)
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return WebAssembly::SET_LOCAL_I32;
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if (RC == &WebAssembly::I64RegClass)
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return WebAssembly::SET_LOCAL_I64;
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if (RC == &WebAssembly::F32RegClass)
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return WebAssembly::SET_LOCAL_F32;
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if (RC == &WebAssembly::F64RegClass)
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return WebAssembly::SET_LOCAL_F64;
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if (RC == &WebAssembly::V128RegClass)
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return WebAssembly::SET_LOCAL_V128;
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llvm_unreachable("Unexpected register class");
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}
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/// Get the appropriate tee_local opcode for the given register class.
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static unsigned getTeeLocalOpcode(const TargetRegisterClass *RC) {
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if (RC == &WebAssembly::I32RegClass)
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return WebAssembly::TEE_LOCAL_I32;
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if (RC == &WebAssembly::I64RegClass)
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return WebAssembly::TEE_LOCAL_I64;
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if (RC == &WebAssembly::F32RegClass)
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return WebAssembly::TEE_LOCAL_F32;
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if (RC == &WebAssembly::F64RegClass)
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return WebAssembly::TEE_LOCAL_F64;
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if (RC == &WebAssembly::V128RegClass)
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return WebAssembly::TEE_LOCAL_V128;
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llvm_unreachable("Unexpected register class");
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}
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/// Get the type associated with the given register class.
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static MVT typeForRegClass(const TargetRegisterClass *RC) {
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if (RC == &WebAssembly::I32RegClass)
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return MVT::i32;
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if (RC == &WebAssembly::I64RegClass)
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return MVT::i64;
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if (RC == &WebAssembly::F32RegClass)
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return MVT::f32;
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if (RC == &WebAssembly::F64RegClass)
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return MVT::f64;
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llvm_unreachable("unrecognized register class");
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}
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/// Given a MachineOperand of a stackified vreg, return the instruction at the
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/// start of the expression tree.
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static MachineInstr *FindStartOfTree(MachineOperand &MO,
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MachineRegisterInfo &MRI,
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WebAssemblyFunctionInfo &MFI) {
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unsigned Reg = MO.getReg();
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assert(MFI.isVRegStackified(Reg));
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MachineInstr *Def = MRI.getVRegDef(Reg);
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// Find the first stackified use and proceed from there.
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for (MachineOperand &DefMO : Def->explicit_uses()) {
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if (!DefMO.isReg())
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continue;
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return FindStartOfTree(DefMO, MRI, MFI);
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}
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// If there were no stackified uses, we've reached the start.
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return Def;
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}
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bool WebAssemblyExplicitLocals::runOnMachineFunction(MachineFunction &MF) {
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DEBUG(dbgs() << "********** Make Locals Explicit **********\n"
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"********** Function: "
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<< MF.getName() << '\n');
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// Disable this pass if we aren't doing direct wasm object emission.
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if (MF.getSubtarget<WebAssemblySubtarget>()
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.getTargetTriple().isOSBinFormatELF())
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return false;
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bool Changed = false;
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MachineRegisterInfo &MRI = MF.getRegInfo();
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WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
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const auto *TII = MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
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// Map non-stackified virtual registers to their local ids.
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DenseMap<unsigned, unsigned> Reg2Local;
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// Handle ARGUMENTS first to ensure that they get the designated numbers.
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for (MachineBasicBlock::iterator I = MF.begin()->begin(),
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E = MF.begin()->end();
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I != E;) {
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MachineInstr &MI = *I++;
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if (!WebAssembly::isArgument(MI))
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break;
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unsigned Reg = MI.getOperand(0).getReg();
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assert(!MFI.isVRegStackified(Reg));
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Reg2Local[Reg] = MI.getOperand(1).getImm();
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MI.eraseFromParent();
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Changed = true;
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}
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// Start assigning local numbers after the last parameter.
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unsigned CurLocal = MFI.getParams().size();
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// Visit each instruction in the function.
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for (MachineBasicBlock &MBB : MF) {
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for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end(); I != E;) {
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MachineInstr &MI = *I++;
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assert(!WebAssembly::isArgument(MI));
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if (MI.isDebugValue() || MI.isLabel())
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continue;
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// Replace tee instructions with tee_local. The difference is that tee
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// instructins have two defs, while tee_local instructions have one def
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// and an index of a local to write to.
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if (WebAssembly::isTee(MI)) {
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assert(MFI.isVRegStackified(MI.getOperand(0).getReg()));
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assert(!MFI.isVRegStackified(MI.getOperand(1).getReg()));
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unsigned OldReg = MI.getOperand(2).getReg();
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const TargetRegisterClass *RC = MRI.getRegClass(OldReg);
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// Stackify the input if it isn't stackified yet.
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if (!MFI.isVRegStackified(OldReg)) {
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unsigned LocalId = getLocalId(Reg2Local, CurLocal, OldReg);
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unsigned NewReg = MRI.createVirtualRegister(RC);
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unsigned Opc = getGetLocalOpcode(RC);
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BuildMI(MBB, &MI, MI.getDebugLoc(), TII->get(Opc), NewReg)
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.addImm(LocalId);
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MI.getOperand(2).setReg(NewReg);
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MFI.stackifyVReg(NewReg);
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}
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// Replace the TEE with a TEE_LOCAL.
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unsigned LocalId =
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getLocalId(Reg2Local, CurLocal, MI.getOperand(1).getReg());
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unsigned Opc = getTeeLocalOpcode(RC);
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BuildMI(MBB, &MI, MI.getDebugLoc(), TII->get(Opc),
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MI.getOperand(0).getReg())
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.addImm(LocalId)
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.addReg(MI.getOperand(2).getReg());
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MI.eraseFromParent();
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Changed = true;
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continue;
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}
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// Insert set_locals for any defs that aren't stackified yet. Currently
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// we handle at most one def.
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assert(MI.getDesc().getNumDefs() <= 1);
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if (MI.getDesc().getNumDefs() == 1) {
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unsigned OldReg = MI.getOperand(0).getReg();
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if (!MFI.isVRegStackified(OldReg) && !MRI.use_empty(OldReg)) {
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unsigned LocalId = getLocalId(Reg2Local, CurLocal, OldReg);
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const TargetRegisterClass *RC = MRI.getRegClass(OldReg);
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unsigned NewReg = MRI.createVirtualRegister(RC);
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auto InsertPt = std::next(MachineBasicBlock::iterator(&MI));
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unsigned Opc = getSetLocalOpcode(RC);
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BuildMI(MBB, InsertPt, MI.getDebugLoc(), TII->get(Opc))
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.addImm(LocalId)
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.addReg(NewReg);
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MI.getOperand(0).setReg(NewReg);
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MFI.stackifyVReg(NewReg);
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Changed = true;
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}
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}
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// Insert get_locals for any uses that aren't stackified yet.
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MachineInstr *InsertPt = &MI;
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for (MachineOperand &MO : reverse(MI.explicit_uses())) {
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if (!MO.isReg())
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continue;
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unsigned OldReg = MO.getReg();
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// If we see a stackified register, prepare to insert subsequent
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// get_locals before the start of its tree.
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if (MFI.isVRegStackified(OldReg)) {
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InsertPt = FindStartOfTree(MO, MRI, MFI);
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continue;
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}
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// Insert a get_local.
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unsigned LocalId = getLocalId(Reg2Local, CurLocal, OldReg);
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const TargetRegisterClass *RC = MRI.getRegClass(OldReg);
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unsigned NewReg = MRI.createVirtualRegister(RC);
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unsigned Opc = getGetLocalOpcode(RC);
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InsertPt =
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BuildMI(MBB, InsertPt, MI.getDebugLoc(), TII->get(Opc), NewReg)
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.addImm(LocalId);
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MO.setReg(NewReg);
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MFI.stackifyVReg(NewReg);
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Changed = true;
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}
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// Coalesce and eliminate COPY instructions.
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if (WebAssembly::isCopy(MI)) {
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MRI.replaceRegWith(MI.getOperand(1).getReg(),
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MI.getOperand(0).getReg());
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MI.eraseFromParent();
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Changed = true;
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}
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}
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}
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// Define the locals.
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for (size_t i = 0, e = MRI.getNumVirtRegs(); i < e; ++i) {
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unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
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auto I = Reg2Local.find(Reg);
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if (I == Reg2Local.end() || I->second < MFI.getParams().size())
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continue;
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MFI.addLocal(typeForRegClass(MRI.getRegClass(Reg)));
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Changed = true;
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}
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#ifndef NDEBUG
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// Assert that all registers have been stackified at this point.
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for (const MachineBasicBlock &MBB : MF) {
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for (const MachineInstr &MI : MBB) {
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if (MI.isDebugValue() || MI.isLabel())
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continue;
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for (const MachineOperand &MO : MI.explicit_operands()) {
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assert(
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(!MO.isReg() || MRI.use_empty(MO.getReg()) ||
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MFI.isVRegStackified(MO.getReg())) &&
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"WebAssemblyExplicitLocals failed to stackify a register operand");
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}
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}
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}
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#endif
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return Changed;
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}
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