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ARM: remove unnecessary state-tracking during frame lowering.

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ResolveFrameIndex had what appeared to be a very nasty hack for when the
frame-index referred to a callee-saved register. In this case it "adjusted" the
offset so that the address was correct if (and only if) the MachineInstr
immediately followed the respective push.

This "worked" for all forms of GPR & DPR but was only ever used to set the
frame pointer itself, and once this was put in a more sensible location the
entire state-tracking machinery it relied on became redundant. So I stripped
it.

The only wrinkle is that "add r7, sp, #0" might theoretically be slower (need
an actual ALU slot) compared to "mov r7, sp" so I added a micro-optimisation
that also makes emitARMRegUpdate and emitT2RegUpdate also work when NumBytes ==
0.

No test changes since there shouldn't be any functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194025 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tim Northover
2013-11-04 23:04:15 +00:00
parent 627ef0cf5e
commit e53abc2072
6 changed files with 58 additions and 115 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
lib/Target/ARM/Thumb1FrameLowering.cpp
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@@ -127,7 +127,6 @@ void Thumb1FrameLowering::emitPrologue(MachineFunction &MF) const {
case ARM::LR:
if (Reg == FramePtr)
FramePtrSpillFI = FI;
AFI->addGPRCalleeSavedArea1Frame(FI);
GPRCS1Size += 4;
break;
case ARM::R8:
@@ -136,16 +135,12 @@ void Thumb1FrameLowering::emitPrologue(MachineFunction &MF) const {
case ARM::R11:
if (Reg == FramePtr)
FramePtrSpillFI = FI;
if (STI.isTargetIOS()) {
AFI->addGPRCalleeSavedArea2Frame(FI);
if (STI.isTargetIOS())
GPRCS2Size += 4;
} else {
AFI->addGPRCalleeSavedArea1Frame(FI);
else
GPRCS1Size += 4;
}
break;
default:
AFI->addDPRCalleeSavedAreaFrame(FI);
DPRCSSize += 8;
}
}
@@ -171,8 +166,9 @@ void Thumb1FrameLowering::emitPrologue(MachineFunction &MF) const {
// Adjust FP so it point to the stack slot that contains the previous FP.
if (HasFP) {
int FramePtrOffset = MFI->getObjectOffset(FramePtrSpillFI) + GPRCS1Size;
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tADDrSPi), FramePtr)
.addFrameIndex(FramePtrSpillFI).addImm(0)
.addReg(ARM::SP).addImm(FramePtrOffset / 4)
.setMIFlags(MachineInstr::FrameSetup));
if (NumBytes > 508)
// If offset is > 508 then sp cannot be adjusted in a single instruction,