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Special epilogue for vararg functions. We cannot do a pop to pc because 

there follows a sp increment for the va register save region. Instead issue
a separate pop to another register, increment sp, and then return:
        pop {r4, r5, r6, r7}
        pop {r3}
        add sp, #3 * 4
        bx r3

llvm-svn: 33739
This commit is contained in:
Evan Cheng 2007-02-01 01:49:46 +00:00
parent df4e992af8
commit e7e966de5e
2 changed files with 24 additions and 5 deletions
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5
llvm/lib/Target/ARM/ARMInstrThumb.td
View File

@ -165,8 +165,11 @@ def tPICADD : TIt<(ops GPR:$dst, GPR:$lhs, pclabel:$cp),
// Control Flow Instructions.
//
let isReturn = 1, isTerminator = 1 in
let isReturn = 1, isTerminator = 1 in {
def tBX_RET : TI<(ops), "bx lr", [(ARMretflag)]>;
// Alternative return instruction used by vararg functions.
def tBX_RET_vararg : TI<(ops GPR:$dst), "bx $dst", []>;
}
// FIXME: remove when we have a way to marking a MI with these properties.
let isLoad = 1, isReturn = 1, isTerminator = 1 in

24
llvm/lib/Target/ARM/ARMRegisterInfo.cpp
View File

@ -104,11 +104,15 @@ bool ARMRegisterInfo::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
if (!AFI->isThumbFunction() || CSI.empty())
return false;
bool isVarArg = AFI->getVarArgsRegSaveSize() > 0;
MachineInstr *PopMI = new MachineInstr(TII.get(ARM::tPOP));
MBB.insert(MI, PopMI);
for (unsigned i = CSI.size(); i != 0; --i) {
unsigned Reg = CSI[i-1].getReg();
if (Reg == ARM::LR) {
// Special epilogue for vararg functions. See emitEpilogue
if (isVarArg)
continue;
Reg = ARM::PC;
PopMI->setInstrDescriptor(TII.get(ARM::tPOP_RET));
MBB.erase(MI);
@ -1115,9 +1119,15 @@ void ARMRegisterInfo::emitEpilogue(MachineFunction &MF,
NumBytes -= (AFI->getGPRCalleeSavedArea1Size() +
AFI->getGPRCalleeSavedArea2Size() +
AFI->getDPRCalleeSavedAreaSize());
if (isThumb)
emitSPUpdate(MBB, MBBI, NumBytes, isThumb, TII);
else {
if (isThumb) {
if (MBBI->getOpcode() == ARM::tBX_RET &&
&MBB.front() != MBBI &&
prior(MBBI)->getOpcode() == ARM::tPOP) {
MachineBasicBlock::iterator PMBBI = prior(MBBI);
emitSPUpdate(MBB, PMBBI, NumBytes, isThumb, TII);
} else
emitSPUpdate(MBB, MBBI, NumBytes, isThumb, TII);
} else {
// Darwin ABI requires FP to point to the stack slot that contains the
// previous FP.
if (STI.isTargetDarwin() || hasFP(MF)) {
@ -1149,8 +1159,14 @@ void ARMRegisterInfo::emitEpilogue(MachineFunction &MF,
emitSPUpdate(MBB, MBBI, AFI->getGPRCalleeSavedArea1Size(), false, TII);
}
if (VARegSaveSize)
if (VARegSaveSize) {
// Epilogue for vararg functions: pop LR to R3 and branch off it.
// FIXME: Verify this is still ok when R3 is no longer being reserved.
BuildMI(MBB, MBBI, TII.get(ARM::tPOP)).addReg(ARM::R3);
emitSPUpdate(MBB, MBBI, VARegSaveSize, isThumb, TII);
BuildMI(MBB, MBBI, TII.get(ARM::tBX_RET_vararg)).addReg(ARM::R3);
MBB.erase(MBBI);
}
}
unsigned ARMRegisterInfo::getRARegister() const {