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//===-- WebAssemblyRegNumbering.cpp - Register Numbering ------------------===//
//
// 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 which assigns WebAssembly register
/// numbers for CodeGen virtual registers.
///
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
#include "WebAssembly.h"
#include "WebAssemblyMachineFunctionInfo.h"
#include "WebAssemblySubtarget.h"
#include "WebAssemblyUtilities.h"
#include "llvm/ADT/SCCIterator.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineLoopInfo.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-reg-numbering"
namespace {
class WebAssemblyRegNumbering final : public MachineFunctionPass {
StringRef getPassName() const override {
return "WebAssembly Register Numbering";
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
MachineFunctionPass::getAnalysisUsage(AU);
}
bool runOnMachineFunction(MachineFunction &MF) override;
public:
static char ID; // Pass identification, replacement for typeid
WebAssemblyRegNumbering() : MachineFunctionPass(ID) {}
};
} // end anonymous namespace
char WebAssemblyRegNumbering::ID = 0;
INITIALIZE_PASS(WebAssemblyRegNumbering, DEBUG_TYPE,
"Assigns WebAssembly register numbers for virtual registers",
false, false)
FunctionPass *llvm::createWebAssemblyRegNumbering() {
return new WebAssemblyRegNumbering();
}
bool WebAssemblyRegNumbering::runOnMachineFunction(MachineFunction &MF) {
LLVM_DEBUG(dbgs() << "********** Register Numbering **********\n"
"********** Function: "
<< MF.getName() << '\n');
WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
MachineRegisterInfo &MRI = MF.getRegInfo();
MFI.initWARegs();
// WebAssembly argument registers are in the same index space as local
// variables. Assign the numbers for them first.
MachineBasicBlock &EntryMBB = MF.front();
for (MachineInstr &MI : EntryMBB) {
if (!WebAssembly::isArgument(MI.getOpcode()))
break;
int64_t Imm = MI.getOperand(1).getImm();
LLVM_DEBUG(dbgs() << "Arg VReg " << MI.getOperand(0).getReg()
<< " -> WAReg " << Imm << "\n");
MFI.setWAReg(MI.getOperand(0).getReg(), Imm);
}
// Then assign regular WebAssembly registers for all remaining used
// virtual registers. TODO: Consider sorting the registers by frequency of
// use, to maximize usage of small immediate fields.
unsigned NumVRegs = MF.getRegInfo().getNumVirtRegs();
unsigned NumStackRegs = 0;
// Start the numbering for locals after the arg regs
unsigned CurReg = MFI.getParams().size();
for (unsigned VRegIdx = 0; VRegIdx < NumVRegs; ++VRegIdx) {
unsigned VReg = Register::index2VirtReg(VRegIdx);
// Skip unused registers.
if (MRI.use_empty(VReg))
continue;
// Handle stackified registers.
if (MFI.isVRegStackified(VReg)) {
LLVM_DEBUG(dbgs() << "VReg " << VReg << " -> WAReg "
<< (INT32_MIN | NumStackRegs) << "\n");
MFI.setWAReg(VReg, INT32_MIN | NumStackRegs++);
continue;
}
if (MFI.getWAReg(VReg) == WebAssemblyFunctionInfo::UnusedReg) {
LLVM_DEBUG(dbgs() << "VReg " << VReg << " -> WAReg " << CurReg << "\n");
MFI.setWAReg(VReg, CurReg++);
}
}
return true;
}
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