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//=--- RegUsageInfoPropagate.cpp - Register Usage Informartion Propagation --=//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// 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/PassAnalysisSupport.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include <map>
#include <string>
namespace llvm {
void initializeRegUsageInfoPropagationPassPass(PassRegistry &);
}
using namespace llvm;
#define DEBUG_TYPE "ip-regalloc"
#define RUIP_NAME "Register Usage Information Propagation"
namespace {
class RegUsageInfoPropagationPass : public MachineFunctionPass {
public:
RegUsageInfoPropagationPass() : MachineFunctionPass(ID) {
PassRegistry &Registry = *PassRegistry::getPassRegistry();
initializeRegUsageInfoPropagationPassPass(Registry);
}
StringRef getPassName() const override { return RUIP_NAME; }
bool runOnMachineFunction(MachineFunction &MF) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
static char ID;
private:
static void setRegMask(MachineInstr &MI, const uint32_t *RegMask) {
for (MachineOperand &MO : MI.operands()) {
if (MO.isRegMask())
MO.setRegMask(RegMask);
}
}
};
} // end of anonymous namespace
char RegUsageInfoPropagationPass::ID = 0;
INITIALIZE_PASS_BEGIN(RegUsageInfoPropagationPass, "reg-usage-propagation",
RUIP_NAME, false, false)
INITIALIZE_PASS_DEPENDENCY(PhysicalRegisterUsageInfo)
INITIALIZE_PASS_END(RegUsageInfoPropagationPass, "reg-usage-propagation",
RUIP_NAME, false, false)
FunctionPass *llvm::createRegUsageInfoPropPass() {
return new RegUsageInfoPropagationPass();
}
void RegUsageInfoPropagationPass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<PhysicalRegisterUsageInfo>();
AU.setPreservesAll();
MachineFunctionPass::getAnalysisUsage(AU);
}
// Assumes call instructions have a single reference to a function.
static const Function *findCalledFunction(const Module &M, MachineInstr &MI) {
for (MachineOperand &MO : MI.operands()) {
if (MO.isGlobal())
return dyn_cast<Function>(MO.getGlobal());
if (MO.isSymbol())
return M.getFunction(MO.getSymbolName());
}
return nullptr;
}
bool RegUsageInfoPropagationPass::runOnMachineFunction(MachineFunction &MF) {
const Module *M = MF.getFunction().getParent();
PhysicalRegisterUsageInfo *PRUI = &getAnalysis<PhysicalRegisterUsageInfo>();
DEBUG(dbgs() << " ++++++++++++++++++++ " << getPassName()
<< " ++++++++++++++++++++ \n");
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;
DEBUG(dbgs()
<< "Call Instruction Before Register Usage Info Propagation : \n");
DEBUG(dbgs() << MI << "\n");
auto UpdateRegMask = [&](const Function *F) {
const auto *RegMask = PRUI->getRegUsageInfo(F);
if (!RegMask)
return;
setRegMask(MI, &(*RegMask)[0]);
Changed = true;
};
if (const Function *F = findCalledFunction(*M, MI)) {
UpdateRegMask(F);
} else {
DEBUG(dbgs() << "Failed to find call target function\n");
}
DEBUG(dbgs() << "Call Instruction After Register Usage Info Propagation : "
<< MI << '\n');
}
}
DEBUG(dbgs() << " +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++"
"++++++ \n");
return Changed;
}
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