Fix epilogue codegen to avoid leaving the stack pointer in an invalid
state. Previously Thumb2 would restore sp from fp like this:
mov sp, r7
sub, sp, #4
If an interrupt is taken after the 'mov' but before the 'sub', callee-saved
registers might be clobbered by the interrupt handler. Instead, try
restoring directly from sp:
add sp, #4
Or, if necessary (with VLA, etc.) use a scratch register to compute sp and
then restore it:
sub.w r4, r7, #8
mov sp, r7
rdar://8465407
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119977 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/Thumb1FrameInfo.cpp b/lib/Target/ARM/Thumb1FrameInfo.cpp
index 6a3c1e1..bb1faf5 100644
--- a/lib/Target/ARM/Thumb1FrameInfo.cpp
+++ b/lib/Target/ARM/Thumb1FrameInfo.cpp
@@ -17,6 +17,7 @@
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
using namespace llvm;
@@ -117,13 +118,6 @@
dl = MBBI->getDebugLoc();
}
- // Adjust FP so it point to the stack slot that contains the previous FP.
- if (hasFP(MF)) {
- BuildMI(MBB, MBBI, dl, TII.get(ARM::tADDrSPi), FramePtr)
- .addFrameIndex(FramePtrSpillFI).addImm(0);
- AFI->setShouldRestoreSPFromFP(true);
- }
-
// Determine starting offsets of spill areas.
unsigned DPRCSOffset = NumBytes - (GPRCS1Size + GPRCS2Size + DPRCSSize);
unsigned GPRCS2Offset = DPRCSOffset + DPRCSSize;
@@ -132,12 +126,21 @@
AFI->setGPRCalleeSavedArea1Offset(GPRCS1Offset);
AFI->setGPRCalleeSavedArea2Offset(GPRCS2Offset);
AFI->setDPRCalleeSavedAreaOffset(DPRCSOffset);
-
NumBytes = DPRCSOffset;
- if (NumBytes) {
+
+ // Adjust FP so it point to the stack slot that contains the previous FP.
+ if (hasFP(MF)) {
+ BuildMI(MBB, MBBI, dl, TII.get(ARM::tADDrSPi), FramePtr)
+ .addFrameIndex(FramePtrSpillFI).addImm(0);
+ if (NumBytes > 7)
+ // If offset is > 7 then sp cannot be adjusted in a single instruction,
+ // try restoring from fp instead.
+ AFI->setShouldRestoreSPFromFP(true);
+ }
+
+ if (NumBytes)
// Insert it after all the callee-save spills.
emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -NumBytes);
- }
if (STI.isTargetELF() && hasFP(MF))
MFI->setOffsetAdjustment(MFI->getOffsetAdjustment() -
@@ -219,10 +222,14 @@
NumBytes = AFI->getFramePtrSpillOffset() - NumBytes;
// Reset SP based on frame pointer only if the stack frame extends beyond
// frame pointer stack slot or target is ELF and the function has FP.
- if (NumBytes)
- emitThumbRegPlusImmediate(MBB, MBBI, ARM::SP, FramePtr, -NumBytes,
+ if (NumBytes) {
+ assert(MF.getRegInfo().isPhysRegUsed(ARM::R4) &&
+ "No scratch register to restore SP from FP!");
+ emitThumbRegPlusImmediate(MBB, MBBI, ARM::R4, FramePtr, -NumBytes,
TII, *RegInfo, dl);
- else
+ BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVtgpr2gpr), ARM::SP)
+ .addReg(ARM::R4);
+ } else
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVtgpr2gpr), ARM::SP)
.addReg(FramePtr);
} else {