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Simplified logic of this if-then statement to reduce nesting. No functionality

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change.

llvm-svn: 73143
This commit is contained in:
Bill Wendling 2009-06-09 20:08:51 +00:00
parent 996a7f7f37
commit 23d6f0b5c7
1 changed files with 48 additions and 46 deletions
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94
lib/Target/X86/X86RegisterInfo.cpp
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@ -838,55 +838,57 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
if (MBBI != MBB.end()) if (MBBI != MBB.end())
DL = MBBI->getDebugLoc(); DL = MBBI->getDebugLoc();
if (NumBytes) { // adjust stack pointer: ESP -= numbytes // Adjust stack pointer: ESP -= numbytes.
if (NumBytes >= 4096 && Subtarget->isTargetCygMing()) { if (NumBytes >= 4096 && Subtarget->isTargetCygMing()) {
// Check, whether EAX is livein for this function // Check, whether EAX is livein for this function.
bool isEAXAlive = false; bool isEAXAlive = false;
for (MachineRegisterInfo::livein_iterator for (MachineRegisterInfo::livein_iterator
II = MF.getRegInfo().livein_begin(), II = MF.getRegInfo().livein_begin(),
EE = MF.getRegInfo().livein_end(); (II != EE) && !isEAXAlive; ++II) { EE = MF.getRegInfo().livein_end(); (II != EE) && !isEAXAlive; ++II) {
unsigned Reg = II->first; unsigned Reg = II->first;
isEAXAlive = (Reg == X86::EAX || Reg == X86::AX || isEAXAlive = (Reg == X86::EAX || Reg == X86::AX ||
Reg == X86::AH || Reg == X86::AL); Reg == X86::AH || Reg == X86::AL);
}
// Function prologue calls _alloca to probe the stack when allocating
// more than 4k bytes in one go. Touching the stack at 4K increments is
// necessary to ensure that the guard pages used by the OS virtual memory
// manager are allocated in correct sequence.
if (!isEAXAlive) {
BuildMI(MBB, MBBI, DL, TII.get(X86::MOV32ri), X86::EAX)
.addImm(NumBytes);
BuildMI(MBB, MBBI, DL, TII.get(X86::CALLpcrel32))
.addExternalSymbol("_alloca");
} else {
// Save EAX
BuildMI(MBB, MBBI, DL, TII.get(X86::PUSH32r))
.addReg(X86::EAX, RegState::Kill);
// Allocate NumBytes-4 bytes on stack. We'll also use 4 already
// allocated bytes for EAX.
BuildMI(MBB, MBBI, DL,
TII.get(X86::MOV32ri), X86::EAX).addImm(NumBytes-4);
BuildMI(MBB, MBBI, DL, TII.get(X86::CALLpcrel32))
.addExternalSymbol("_alloca");
// Restore EAX
MachineInstr *MI = addRegOffset(BuildMI(MF, DL, TII.get(X86::MOV32rm),
X86::EAX),
StackPtr, false, NumBytes-4);
MBB.insert(MBBI, MI);
}
} else {
// If there is an SUB32ri of ESP immediately before this instruction,
// merge the two. This can be the case when tail call elimination is
// enabled and the callee has more arguments then the caller.
NumBytes -= mergeSPUpdates(MBB, MBBI, StackPtr, true);
// If there is an ADD32ri or SUB32ri of ESP immediately after this
// instruction, merge the two instructions.
mergeSPUpdatesDown(MBB, MBBI, StackPtr, &NumBytes);
if (NumBytes)
emitSPUpdate(MBB, MBBI, StackPtr, -(int64_t)NumBytes, Is64Bit, TII);
} }
// Function prologue calls _alloca to probe the stack when allocating more
// than 4k bytes in one go. Touching the stack at 4K increments is necessary
// to ensure that the guard pages used by the OS virtual memory manager are
// allocated in correct sequence.
if (!isEAXAlive) {
BuildMI(MBB, MBBI, DL, TII.get(X86::MOV32ri), X86::EAX)
.addImm(NumBytes);
BuildMI(MBB, MBBI, DL, TII.get(X86::CALLpcrel32))
.addExternalSymbol("_alloca");
} else {
// Save EAX
BuildMI(MBB, MBBI, DL, TII.get(X86::PUSH32r))
.addReg(X86::EAX, RegState::Kill);
// Allocate NumBytes-4 bytes on stack. We'll also use 4 already
// allocated bytes for EAX.
BuildMI(MBB, MBBI, DL, TII.get(X86::MOV32ri), X86::EAX)
.addImm(NumBytes - 4);
BuildMI(MBB, MBBI, DL, TII.get(X86::CALLpcrel32))
.addExternalSymbol("_alloca");
// Restore EAX
MachineInstr *MI = addRegOffset(BuildMI(MF, DL, TII.get(X86::MOV32rm),
X86::EAX),
StackPtr, false, NumBytes - 4);
MBB.insert(MBBI, MI);
}
} else if (NumBytes) {
// If there is an SUB32ri of ESP immediately before this instruction, merge
// the two. This can be the case when tail call elimination is enabled and
// the callee has more arguments then the caller.
NumBytes -= mergeSPUpdates(MBB, MBBI, StackPtr, true);
// If there is an ADD32ri or SUB32ri of ESP immediately after this
// instruction, merge the two instructions.
mergeSPUpdatesDown(MBB, MBBI, StackPtr, &NumBytes);
if (NumBytes)
emitSPUpdate(MBB, MBBI, StackPtr, -(int64_t)NumBytes, Is64Bit, TII);
} }
if (needsFrameMoves) if (needsFrameMoves)