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Save and restore LR just like any other register and ONLY if we actually modify

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it (due to calls or globals access).  We now compile `void empty(){}' to `blr'.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@15274 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Misha Brukman 2004-07-27 17:17:18 +00:00
parent e862f306fb
commit 9a771d55fe
1 changed files with 20 additions and 11 deletions
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31
lib/Target/PowerPC/PowerPCRegisterInfo.cpp
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@ -62,19 +62,34 @@ PowerPCRegisterInfo::storeRegToStackSlot(MachineBasicBlock &MBB,
PPC32::STB, PPC32::STH, PPC32::STW, PPC32::STFS, PPC32::STFD
};
unsigned OC = Opcode[getIdx(RC)];
if (SrcReg == PPC32::LR) {
MBB.insert(MI, BuildMI(PPC32::MFLR, 0, PPC32::R0));
OC = PPC32::STW;
SrcReg = PPC32::R0;
}
MBB.insert(MI, addFrameReference(BuildMI(OC, 3).addReg(SrcReg),FrameIdx));
return 1;
}
int PowerPCRegisterInfo::loadRegFromStackSlot(MachineBasicBlock &MBB,
int
PowerPCRegisterInfo::loadRegFromStackSlot(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
unsigned DestReg, int FrameIdx,
const TargetRegisterClass *RC) const{
const TargetRegisterClass *RC) const {
static const unsigned Opcode[] = {
PPC32::LBZ, PPC32::LHZ, PPC32::LWZ, PPC32::LFS, PPC32::LFD
};
unsigned OC = Opcode[getIdx(RC)];
bool LoadLR = false;
if (DestReg == PPC32::LR) {
DestReg = PPC32::R0;
LoadLR = true;
OC = PPC32::LWZ;
}
MBB.insert(MI, addFrameReference(BuildMI(OC, 2, DestReg), FrameIdx));
if (LoadLR)
MBB.insert(MI, BuildMI(PPC32::MTLR, 1).addReg(PPC32::R0));
return 1;
}
@ -186,14 +201,11 @@ void PowerPCRegisterInfo::emitPrologue(MachineFunction &MF) const {
// Get the number of bytes to allocate from the FrameInfo
unsigned NumBytes = MFI->getStackSize();
// FIXME: the assembly printer inserts "calls" aka branch-and-link to get the
// PC address. We may not know about those calls at this time, so be
// conservative.
if (MFI->hasCalls() || true) {
// If we have calls, save the LR value on the stack
if (MFI->hasCalls()) {
// When we have no frame pointer, we reserve argument space for call sites
// in the function immediately on entry to the current function. This
// eliminates the need for add/sub brackets around call sites.
//
NumBytes += MFI->getMaxCallFrameSize() +
24 + // Predefined PowerPC link area
32 + // Predefined PowerPC params area
@ -249,10 +261,7 @@ void PowerPCRegisterInfo::emitEpilogue(MachineFunction &MF,
unsigned NumBytes = MFI->getStackSize();
// If we have calls, restore the LR value before we branch to it
// FIXME: the assembly printer inserts "calls" aka branch-and-link to get the
// PC address. We may not know about those calls at this time, so be
// conservative.
if (MFI->hasCalls() || true) {
if (MFI->hasCalls()) {
// Restore LR
MI = BuildMI(PPC32::LWZ, 2,PPC32::R0).addSImm(NumBytes+8).addReg(PPC32::R1);
MBB.insert(MBBI, MI);