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//===-- WebAssemblyLowerBrUnless.cpp - Lower br_unless --------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// \file
/// \brief This file lowers br_unless into br_if with an inverted condition.
///
/// br_unless is not currently in the spec, but it's very convenient for LLVM
/// to use. This pass allows LLVM to use it, for now.
///
//===----------------------------------------------------------------------===//
#include "WebAssembly.h"
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
#include "WebAssemblyMachineFunctionInfo.h"
#include "WebAssemblySubtarget.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DEBUG_TYPE "wasm-lower-br_unless"
namespace {
class WebAssemblyLowerBrUnless final : public MachineFunctionPass {
const char *getPassName() const override {
return "WebAssembly Lower br_unless";
}
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
WebAssemblyLowerBrUnless() : MachineFunctionPass(ID) {}
};
} // end anonymous namespace
char WebAssemblyLowerBrUnless::ID = 0;
FunctionPass *llvm::createWebAssemblyLowerBrUnless() {
return new WebAssemblyLowerBrUnless();
}
bool WebAssemblyLowerBrUnless::runOnMachineFunction(MachineFunction &MF) {
DEBUG(dbgs() << "********** Lowering br_unless **********\n"
"********** Function: "
<< MF.getName() << '\n');
auto &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
auto &MRI = MF.getRegInfo();
for (auto &MBB : MF) {
for (auto MII = MBB.begin(); MII != MBB.end();) {
MachineInstr *MI = &*MII++;
if (MI->getOpcode() != WebAssembly::BR_UNLESS)
continue;
unsigned Cond = MI->getOperand(1).getReg();
bool Inverted = false;
// Attempt to invert the condition in place.
if (MFI.isVRegStackified(Cond)) {
assert(MRI.hasOneDef(Cond));
MachineInstr *Def = MRI.getVRegDef(Cond);
switch (Def->getOpcode()) {
using namespace WebAssembly;
case EQ_I32: Def->setDesc(TII.get(NE_I32)); Inverted = true; break;
case NE_I32: Def->setDesc(TII.get(EQ_I32)); Inverted = true; break;
case GT_S_I32: Def->setDesc(TII.get(LE_S_I32)); Inverted = true; break;
case GE_S_I32: Def->setDesc(TII.get(LT_S_I32)); Inverted = true; break;
case LT_S_I32: Def->setDesc(TII.get(GE_S_I32)); Inverted = true; break;
case LE_S_I32: Def->setDesc(TII.get(GT_S_I32)); Inverted = true; break;
case GT_U_I32: Def->setDesc(TII.get(LE_U_I32)); Inverted = true; break;
case GE_U_I32: Def->setDesc(TII.get(LT_U_I32)); Inverted = true; break;
case LT_U_I32: Def->setDesc(TII.get(GE_U_I32)); Inverted = true; break;
case LE_U_I32: Def->setDesc(TII.get(GT_U_I32)); Inverted = true; break;
case EQ_I64: Def->setDesc(TII.get(NE_I64)); Inverted = true; break;
case NE_I64: Def->setDesc(TII.get(EQ_I64)); Inverted = true; break;
case GT_S_I64: Def->setDesc(TII.get(LE_S_I64)); Inverted = true; break;
case GE_S_I64: Def->setDesc(TII.get(LT_S_I64)); Inverted = true; break;
case LT_S_I64: Def->setDesc(TII.get(GE_S_I64)); Inverted = true; break;
case LE_S_I64: Def->setDesc(TII.get(GT_S_I64)); Inverted = true; break;
case GT_U_I64: Def->setDesc(TII.get(LE_U_I64)); Inverted = true; break;
case GE_U_I64: Def->setDesc(TII.get(LT_U_I64)); Inverted = true; break;
case LT_U_I64: Def->setDesc(TII.get(GE_U_I64)); Inverted = true; break;
case LE_U_I64: Def->setDesc(TII.get(GT_U_I64)); Inverted = true; break;
case EQ_F32: Def->setDesc(TII.get(NE_F32)); Inverted = true; break;
case NE_F32: Def->setDesc(TII.get(EQ_F32)); Inverted = true; break;
case EQ_F64: Def->setDesc(TII.get(NE_F64)); Inverted = true; break;
case NE_F64: Def->setDesc(TII.get(EQ_F64)); Inverted = true; break;
default: break;
}
}
// If we weren't able to invert the condition in place. Insert an
// expression to invert it.
if (!Inverted) {
unsigned Tmp = MRI.createVirtualRegister(&WebAssembly::I32RegClass);
MFI.stackifyVReg(Tmp);
BuildMI(MBB, MI, MI->getDebugLoc(), TII.get(WebAssembly::EQZ_I32), Tmp)
.addReg(Cond);
Cond = Tmp;
Inverted = true;
}
// The br_unless condition has now been inverted. Insert a br_if and
// delete the br_unless.
assert(Inverted);
BuildMI(MBB, MI, MI->getDebugLoc(), TII.get(WebAssembly::BR_IF))
.addOperand(MI->getOperand(0))
.addReg(Cond);
MBB.erase(MI);
}
}
return true;
}
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