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//===- NVPTXProxyRegErasure.cpp - NVPTX Proxy Register Instruction Erasure -==//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// The pass is needed to remove ProxyReg instructions and restore related
// registers. The instructions were needed at instruction selection stage to
// make sure that callseq_end nodes won't be removed as "dead nodes". This can
// happen when we expand instructions into libcalls and the call site doesn't
// care about the libcall chain. Call site cares about data flow only, and the
// latest data flow node happens to be before callseq_end. Therefore the node
// becomes dangling and "dead". The ProxyReg acts like an additional data flow
// node *after* the callseq_end in the chain and ensures that everything will be
// preserved.
//
//===----------------------------------------------------------------------===//
#include "NVPTX.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
using namespace llvm;
namespace llvm {
void initializeNVPTXProxyRegErasurePass(PassRegistry &);
}
namespace {
struct NVPTXProxyRegErasure : public MachineFunctionPass {
public:
static char ID;
NVPTXProxyRegErasure() : MachineFunctionPass(ID) {
initializeNVPTXProxyRegErasurePass(*PassRegistry::getPassRegistry());
}
bool runOnMachineFunction(MachineFunction &MF) override;
StringRef getPassName() const override {
return "NVPTX Proxy Register Instruction Erasure";
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
MachineFunctionPass::getAnalysisUsage(AU);
}
private:
void replaceMachineInstructionUsage(MachineFunction &MF, MachineInstr &MI);
void replaceRegisterUsage(MachineInstr &Instr, MachineOperand &From,
MachineOperand &To);
};
} // namespace
char NVPTXProxyRegErasure::ID = 0;
INITIALIZE_PASS(NVPTXProxyRegErasure, "nvptx-proxyreg-erasure", "NVPTX ProxyReg Erasure", false, false)
bool NVPTXProxyRegErasure::runOnMachineFunction(MachineFunction &MF) {
SmallVector<MachineInstr *, 16> RemoveList;
for (auto &BB : MF) {
for (auto &MI : BB) {
switch (MI.getOpcode()) {
case NVPTX::ProxyRegI1:
case NVPTX::ProxyRegI16:
case NVPTX::ProxyRegI32:
case NVPTX::ProxyRegI64:
case NVPTX::ProxyRegF16:
case NVPTX::ProxyRegF16x2:
case NVPTX::ProxyRegF32:
case NVPTX::ProxyRegF64:
replaceMachineInstructionUsage(MF, MI);
RemoveList.push_back(&MI);
break;
}
}
}
for (auto *MI : RemoveList) {
MI->eraseFromParent();
}
return !RemoveList.empty();
}
void NVPTXProxyRegErasure::replaceMachineInstructionUsage(MachineFunction &MF,
MachineInstr &MI) {
auto &InOp = *MI.uses().begin();
auto &OutOp = *MI.defs().begin();
assert(InOp.isReg() && "ProxyReg input operand should be a register.");
assert(OutOp.isReg() && "ProxyReg output operand should be a register.");
for (auto &BB : MF) {
for (auto &I : BB) {
replaceRegisterUsage(I, OutOp, InOp);
}
}
}
void NVPTXProxyRegErasure::replaceRegisterUsage(MachineInstr &Instr,
MachineOperand &From,
MachineOperand &To) {
for (auto &Op : Instr.uses()) {
if (Op.isReg() && Op.getReg() == From.getReg()) {
Op.setReg(To.getReg());
}
}
}
MachineFunctionPass *llvm::createNVPTXProxyRegErasurePass() {
return new NVPTXProxyRegErasure();
}
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