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//===- ReduceRegisterUses.cpp - Specialized Delta Pass --------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file implements a function which calls the Generic Delta pass in order
// to reduce uninteresting register uses from the MachineFunction.
//
//===----------------------------------------------------------------------===//
#include "ReduceRegisterUses.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
using namespace llvm;
static void removeUsesFromFunction(Oracle &O, MachineFunction &MF) {
MachineRegisterInfo &MRI = MF.getRegInfo();
for (MachineBasicBlock &MBB : MF) {
for (MachineInstr &MI : MBB) {
// Generic instructions are not supposed to have undef operands.
if (isPreISelGenericOpcode(MI.getOpcode()))
continue;
int NumOperands = MI.getNumOperands();
int NumRequiredOps = MI.getNumExplicitOperands() +
MI.getDesc().implicit_defs().size() +
MI.getDesc().implicit_uses().size();
for (int I = NumOperands - 1; I >= 0; --I) {
MachineOperand &MO = MI.getOperand(I);
if (!MO.isReg() || !MO.readsReg())
continue;
Register Reg = MO.getReg();
if (Reg.isPhysical() && MRI.isReserved(Reg))
continue;
if (O.shouldKeep())
continue;
// Remove implicit operands. If the register is part of the fixed
// operand list, set to undef.
if (I >= NumRequiredOps)
MI.removeOperand(I);
else
MO.setIsUndef();
}
}
}
}
static void removeUsesFromModule(Oracle &O, ReducerWorkItem &WorkItem) {
for (const Function &F : WorkItem.getModule()) {
if (auto *MF = WorkItem.MMI->getMachineFunction(F))
removeUsesFromFunction(O, *MF);
}
}
void llvm::reduceRegisterUsesMIRDeltaPass(TestRunner &Test) {
runDeltaPass(Test, removeUsesFromModule, "Reducing register uses");
}
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