[AArch64][DebugInfo] Do not recompute CalleeSavedStackSize

This patch fixes a bug exposed by D65653 where a subsequent invocation
of `determineCalleeSaves` ends up with a different size for the callee
save area, leading to different frame-offsets in debug information.

In the invocation by PEI, `determineCalleeSaves` tries to determine
whether it needs to spill an extra callee-saved register to get an
emergency spill slot. To do this, it calls 'estimateStackSize' and
manually adds the size of the callee-saves to this. PEI then allocates
the spill objects for the callee saves and the remaining frame layout
is calculated accordingly.

A second invocation in LiveDebugValues causes estimateStackSize to return
the size of the stack frame including the callee-saves. Given that the
size of the callee-saves is added to this, these callee-saves are counted
twice, which leads `determineCalleeSaves` to believe the stack has
become big enough to require spilling an extra callee-save as emergency
spillslot. It then updates CalleeSavedStackSize with a larger value.

Since CalleeSavedStackSize is used in the calculation of the frame
offset in getFrameIndexReference, this leads to incorrect offsets for
variables/locals when this information is recalculated after PEI.

Reviewers: omjavaid, eli.friedman, thegameg, efriedma

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D66935

llvm-svn: 372204

1 files changed, 1 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/LiveDebugValues.cpp b/llvm/lib/CodeGen/LiveDebugValues.cpp
index 0bdc62a345c..5e5c627caf1 100644
--- a/llvm/lib/CodeGen/LiveDebugValues.cpp
+++ b/llvm/lib/CodeGen/LiveDebugValues.cpp
@@ -1409,8 +1409,7 @@ bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) {
   TRI = MF.getSubtarget().getRegisterInfo();
   TII = MF.getSubtarget().getInstrInfo();
   TFI = MF.getSubtarget().getFrameLowering();
-  TFI->determineCalleeSaves(MF, CalleeSavedRegs,
-                            std::make_unique<RegScavenger>().get());
+  TFI->getCalleeSaves(MF, CalleeSavedRegs);
   LS.initialize(MF);
 
   bool Changed = ExtendRanges(MF);