[AArch64] Fix scavenged spill slot base when stack realignment required.
Summary:
Use the FP for scavenged spill slot accesses to prevent corruption of
the callee-save region when the SP is re-aligned.
Based on problem and patch reported by @paulwalker-arm
This is an alternative to solution proposed in D45770
Reviewers: t.p.northover, paulwalker-arm, thegameg, javed.absar
Subscribers: qcolombet, mcrosier, paulwalker-arm, kristof.beyls, rengolin, javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D46063
llvm-svn: 330976
diff --git a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
index 8575e59..a573e2c 100644
--- a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -1023,6 +1023,8 @@
int FPOffset = MFI.getObjectOffset(FI) + FixedObject + 16;
int Offset = MFI.getObjectOffset(FI) + MFI.getStackSize();
bool isFixed = MFI.isFixedObjectIndex(FI);
+ bool isCSR = !isFixed && MFI.getObjectOffset(FI) >=
+ -((int)AFI->getCalleeSavedStackSize());
// Use frame pointer to reference fixed objects. Use it for locals if
// there are VLAs or a dynamically realigned SP (and thus the SP isn't
@@ -1036,6 +1038,12 @@
// Argument access should always use the FP.
if (isFixed) {
UseFP = hasFP(MF);
+ } else if (isCSR && RegInfo->needsStackRealignment(MF)) {
+ // References to the CSR area must use FP if we're re-aligning the stack
+ // since the dynamically-sized alignment padding is between the SP/BP and
+ // the CSR area.
+ assert(hasFP(MF) && "Re-aligned stack must have frame pointer");
+ UseFP = true;
} else if (hasFP(MF) && !RegInfo->needsStackRealignment(MF)) {
// If the FPOffset is negative, we have to keep in mind that the
// available offset range for negative offsets is smaller than for
@@ -1069,9 +1077,9 @@
}
}
- assert((isFixed || !RegInfo->needsStackRealignment(MF) || !UseFP) &&
+ assert(((isFixed || isCSR) || !RegInfo->needsStackRealignment(MF) || !UseFP) &&
"In the presence of dynamic stack pointer realignment, "
- "non-argument objects cannot be accessed through the frame pointer");
+ "non-argument/CSR objects cannot be accessed through the frame pointer");
if (UseFP) {
FrameReg = RegInfo->getFrameRegister(MF);