Fix AArch64 prologue for empty frame with dynamic allocas.
Fixes PR23804: assertion failure in emitPrologue in the case of a
function with an empty frame and a dynamic alloca that needs stack
realignment. This is a typical case for AddressSanitizer.
llvm-svn: 241943
diff --git a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
index 3ba7e70..2e552cd 100644
--- a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -349,13 +349,12 @@
// Allocate space for the rest of the frame.
const unsigned Alignment = MFI->getMaxAlignment();
- const bool NeedsRealignment = (Alignment > 16);
+ const bool NeedsRealignment = RegInfo->needsStackRealignment(MF);
unsigned scratchSPReg = AArch64::SP;
- if (NeedsRealignment) {
- // Use the first callee-saved register as a scratch register
- assert(MF.getRegInfo().isPhysRegUsed(AArch64::X9) &&
- "No scratch register to align SP!");
+ if (NumBytes && NeedsRealignment) {
+ // Use the first callee-saved register as a scratch register.
scratchSPReg = AArch64::X9;
+ MF.getRegInfo().setPhysRegUsed(scratchSPReg);
}
// If we're a leaf function, try using the red zone.
@@ -366,9 +365,6 @@
emitFrameOffset(MBB, MBBI, DL, scratchSPReg, AArch64::SP, -NumBytes, TII,
MachineInstr::FrameSetup);
- assert(!(NeedsRealignment && NumBytes==0) &&
- "NumBytes should never be 0 when realignment is needed");
-
if (NumBytes && NeedsRealignment) {
const unsigned NrBitsToZero = countTrailingZeros(Alignment);
assert(NrBitsToZero > 1);