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//===-- X86FloatingPoint.cpp - FP_REG_KILL inserter -----------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the pass which inserts FP_REG_KILL instructions.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "x86-codegen"
#include "X86.h"
#include "X86InstrInfo.h"
#include "llvm/Instructions.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/CFG.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;
STATISTIC(NumFPKill, "Number of FP_REG_KILL instructions added");
namespace {
struct FPRegKiller : public MachineFunctionPass {
static char ID;
FPRegKiller() : MachineFunctionPass(&ID) {}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
AU.addPreservedID(MachineLoopInfoID);
AU.addPreservedID(MachineDominatorsID);
MachineFunctionPass::getAnalysisUsage(AU);
}
virtual bool runOnMachineFunction(MachineFunction &MF);
virtual const char *getPassName() const {
return "X86 FP_REG_KILL inserter";
}
};
char FPRegKiller::ID = 0;
}
FunctionPass *llvm::createX87FPRegKillInserterPass() {
return new FPRegKiller();
}
/// isFPStackVReg - Return true if the specified vreg is from a fp stack
/// register class.
static bool isFPStackVReg(unsigned RegNo, const MachineRegisterInfo &MRI) {
if (!TargetRegisterInfo::isVirtualRegister(RegNo))
return false;
switch (MRI.getRegClass(RegNo)->getID()) {
default: return false;
case X86::RFP32RegClassID:
case X86::RFP64RegClassID:
case X86::RFP80RegClassID:
return true;
}
}
/// ContainsFPStackCode - Return true if the specific MBB has floating point
/// stack code, and thus needs an FP_REG_KILL.
static bool ContainsFPStackCode(MachineBasicBlock *MBB,
const MachineRegisterInfo &MRI) {
// Scan the block, looking for instructions that define or use fp stack vregs.
for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
I != E; ++I) {
for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op) {
if (!I->getOperand(op).isReg())
continue;
if (unsigned Reg = I->getOperand(op).getReg())
if (isFPStackVReg(Reg, MRI))
return true;
}
}
// Check PHI nodes in successor blocks. These PHI's will be lowered to have
// a copy of the input value in this block, which is a definition of the
// value.
for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
E = MBB->succ_end(); SI != E; ++ SI) {
MachineBasicBlock *SuccBB = *SI;
for (MachineBasicBlock::iterator I = SuccBB->begin(), E = SuccBB->end();
I != E; ++I) {
// All PHI nodes are at the top of the block.
if (!I->isPHI()) break;
if (isFPStackVReg(I->getOperand(0).getReg(), MRI))
return true;
}
}
return false;
}
bool FPRegKiller::runOnMachineFunction(MachineFunction &MF) {
// If we are emitting FP stack code, scan the basic block to determine if this
// block defines or uses any FP values. If so, put an FP_REG_KILL instruction
// before the terminator of the block.
// Note that FP stack instructions are used in all modes for long double,
// so we always need to do this check.
// Also note that it's possible for an FP stack register to be live across
// an instruction that produces multiple basic blocks (SSE CMOV) so we
// must check all the generated basic blocks.
// Scan all of the machine instructions in these MBBs, checking for FP
// stores. (RFP32 and RFP64 will not exist in SSE mode, but RFP80 might.)
// Fast-path: If nothing is using the x87 registers, we don't need to do
// any scanning.
const MachineRegisterInfo &MRI = MF.getRegInfo();
if (MRI.getRegClassVirtRegs(X86::RFP80RegisterClass).empty() &&
MRI.getRegClassVirtRegs(X86::RFP64RegisterClass).empty() &&
MRI.getRegClassVirtRegs(X86::RFP32RegisterClass).empty())
return false;
bool Changed = false;
MachineFunction::iterator MBBI = MF.begin();
MachineFunction::iterator EndMBB = MF.end();
for (; MBBI != EndMBB; ++MBBI) {
MachineBasicBlock *MBB = MBBI;
// If this block returns, ignore it. We don't want to insert an FP_REG_KILL
// before the return.
if (!MBB->empty()) {
MachineBasicBlock::iterator EndI = MBB->end();
--EndI;
if (EndI->getDesc().isReturn())
continue;
}
// If we find any FP stack code, emit the FP_REG_KILL instruction.
if (ContainsFPStackCode(MBB, MRI)) {
BuildMI(*MBB, MBBI->getFirstTerminator(), DebugLoc(),
MF.getTarget().getInstrInfo()->get(X86::FP_REG_KILL));
++NumFPKill;
Changed = true;
}
}
return Changed;
}
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