When trying to eliminate an "sub sp, sp, #N" instruction by folding
it into an existing push/pop using dummy registers, we need to account
for the fact that this might affect precisely how "fp" gets set in the
prologue.
We were attempting this, but assuming that *whenever* we performed a
fold it would make a difference. This is false, for example, in:
push {r4, r7, lr}
add fp, sp, #4
vpush {d8}
sub sp, sp, #8
we can fold the "sub" into the "vpush", forming "vpush {d7, d8}".
However, in that case the "add fp" instruction mustn't change, which
we were getting wrong before.
Should fix PR18160.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196725
91177308-0d34-0410-b5e6-
96231b3b80d8
if (NumBytes) {
// Adjust SP after all the callee-save spills.
- if (tryFoldSPUpdateIntoPushPop(STI, MF, LastPush, NumBytes))
- FramePtrOffsetInPush += NumBytes;
- else
+ if (tryFoldSPUpdateIntoPushPop(STI, MF, LastPush, NumBytes)) {
+ if (LastPush == FramePtrPush)
+ FramePtrOffsetInPush += NumBytes;
+ } else
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -NumBytes,
MachineInstr::FrameSetup);
; CHECK: {{LBB[0-9]+_2}}:
; CHECK-NEXT: vpop {d7, d8}
; CHECK-NEXT: pop {r4, pc}
+
+ ; With a guaranteed frame-pointer, we want to make sure that its offset in the
+ ; push block is correct, even if a few registers have been tacked onto a later
+ ; vpush (PR18160).
+; CHECK-IOS-LABEL: test_fold_point:
+; CHECK-IOS: push {r4, r7, lr}
+; CHECK-IOS-NEXT: add r7, sp, #4
+; CHECK-IOS-NEXT: vpush {d7, d8}
+
; We want some memory so there's a stack adjustment to fold...
%var = alloca i8, i32 8