RegUsageInfoPropagate.cpp
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//=--- RegUsageInfoPropagate.cpp - Register Usage Informartion Propagation --=//
//
// 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 pass is required to take advantage of the interprocedural register
/// allocation infrastructure.
///
/// This pass iterates through MachineInstrs in a given MachineFunction and at
/// each callsite queries RegisterUsageInfo for RegMask (calculated based on
/// actual register allocation) of the callee function, if the RegMask detail
/// is available then this pass will update the RegMask of the call instruction.
/// This updated RegMask will be used by the register allocator while allocating
/// the current MachineFunction.
///
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/RegisterUsageInfo.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include <map>
#include <string>
using namespace llvm;
#define DEBUG_TYPE "ip-regalloc"
#define RUIP_NAME "Register Usage Information Propagation"
namespace {
class RegUsageInfoPropagation : public MachineFunctionPass {
public:
RegUsageInfoPropagation() : MachineFunctionPass(ID) {
PassRegistry &Registry = *PassRegistry::getPassRegistry();
initializeRegUsageInfoPropagationPass(Registry);
}
StringRef getPassName() const override { return RUIP_NAME; }
bool runOnMachineFunction(MachineFunction &MF) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<PhysicalRegisterUsageInfo>();
AU.setPreservesAll();
MachineFunctionPass::getAnalysisUsage(AU);
}
static char ID;
private:
static void setRegMask(MachineInstr &MI, ArrayRef<uint32_t> RegMask) {
assert(RegMask.size() ==
MachineOperand::getRegMaskSize(MI.getParent()->getParent()
->getRegInfo().getTargetRegisterInfo()
->getNumRegs())
&& "expected register mask size");
for (MachineOperand &MO : MI.operands()) {
if (MO.isRegMask())
MO.setRegMask(RegMask.data());
}
}
};
} // end of anonymous namespace
INITIALIZE_PASS_BEGIN(RegUsageInfoPropagation, "reg-usage-propagation",
RUIP_NAME, false, false)
INITIALIZE_PASS_DEPENDENCY(PhysicalRegisterUsageInfo)
INITIALIZE_PASS_END(RegUsageInfoPropagation, "reg-usage-propagation",
RUIP_NAME, false, false)
char RegUsageInfoPropagation::ID = 0;
// Assumes call instructions have a single reference to a function.
static const Function *findCalledFunction(const Module &M,
const MachineInstr &MI) {
for (const MachineOperand &MO : MI.operands()) {
if (MO.isGlobal())
return dyn_cast<const Function>(MO.getGlobal());
if (MO.isSymbol())
return M.getFunction(MO.getSymbolName());
}
return nullptr;
}
bool RegUsageInfoPropagation::runOnMachineFunction(MachineFunction &MF) {
const Module &M = *MF.getFunction().getParent();
PhysicalRegisterUsageInfo *PRUI = &getAnalysis<PhysicalRegisterUsageInfo>();
LLVM_DEBUG(dbgs() << " ++++++++++++++++++++ " << getPassName()
<< " ++++++++++++++++++++ \n");
LLVM_DEBUG(dbgs() << "MachineFunction : " << MF.getName() << "\n");
const MachineFrameInfo &MFI = MF.getFrameInfo();
if (!MFI.hasCalls() && !MFI.hasTailCall())
return false;
bool Changed = false;
for (MachineBasicBlock &MBB : MF) {
for (MachineInstr &MI : MBB) {
if (!MI.isCall())
continue;
LLVM_DEBUG(
dbgs()
<< "Call Instruction Before Register Usage Info Propagation : \n"
<< MI << "\n");
auto UpdateRegMask = [&](const Function &F) {
const ArrayRef<uint32_t> RegMask = PRUI->getRegUsageInfo(F);
if (RegMask.empty())
return;
setRegMask(MI, RegMask);
Changed = true;
};
if (const Function *F = findCalledFunction(M, MI)) {
if (F->isDefinitionExact()) {
UpdateRegMask(*F);
} else {
LLVM_DEBUG(dbgs() << "Function definition is not exact\n");
}
} else {
LLVM_DEBUG(dbgs() << "Failed to find call target function\n");
}
LLVM_DEBUG(
dbgs()
<< "Call Instruction After Register Usage Info Propagation : \n"
<< MI << '\n');
}
}
LLVM_DEBUG(
dbgs() << " +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++"
"++++++ \n");
return Changed;
}
FunctionPass *llvm::createRegUsageInfoPropPass() {
return new RegUsageInfoPropagation();
}