[AArch64][DebugInfo] Do not recompute CalleeSavedStackSize (Take 2)

[sdesmalen]

Summary

Commit message from D66935:

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.

This patch fixes the lldb unit tests in functionalities/thread/concurrent_events/*

Changes after D66935:

Ensures AArch64FunctionInfo::getCalleeSavedStackSize does not return
the uninitialized CalleeSavedStackSize when running llc on a specific
pass where the MIR code has already been expected to have gone through PEI.

Instead, getCalleeSavedStackSize (when passed the MachineFrameInfo) will try
to recalculate the CalleeSavedStackSize from the CalleeSavedInfo. In debug
mode, the compiler will assert the recalculated size equals the cached
size as calculated through a call to determineCalleeSaves.

This fixes two tests:

test/DebugInfo/AArch64/asan-stack-vars.mir
test/DebugInfo/AArch64/compiler-gen-bbs-livedebugvalues.mir

that otherwise fail when compiled using msan.

[sdesmalen]

llvm/lib/Target/AArch64/AArch64MachineFunctionInfo.h

183

I've tested LNT and the llvm unit-tests with this check enabled.

[omjavaid]

This revision does not fix LLDB regression on AArch64.

http://lab.llvm.org:8014/builders/lldb-aarch64-ubuntu

All tests in functionalities/thread/concurrent_events/* category still failing.

[sdesmalen]

In D68783#1708963, @omjavaid wrote:

This revision does not fix LLDB regression on AArch64.

http://lab.llvm.org:8014/builders/lldb-aarch64-ubuntu

All tests in functionalities/thread/concurrent_events/* category still failing.

Correct, those tests are fixed by D66935. That fix was reverted because of a failure with msan on test/DebugInfo/AArch64/asan-stack-vars.mir and test/DebugInfo/AArch64/compiler-gen-bbs-livedebugvalues.mir, which this patch intends to fix. I kept the fixes separate to make them easier to review. Do you want me to merge the two patches?

[omjavaid]

In D68783#1709000, @sdesmalen wrote:

In D68783#1708963, @omjavaid wrote:

This revision does not fix LLDB regression on AArch64.

http://lab.llvm.org:8014/builders/lldb-aarch64-ubuntu

All tests in functionalities/thread/concurrent_events/* category still failing.

Correct, those tests are fixed by D66935. That fix was reverted because of a failure with msan on test/DebugInfo/AArch64/asan-stack-vars.mir and test/DebugInfo/AArch64/compiler-gen-bbs-livedebugvalues.mir, which this patch intends to fix. I kept the fixes separate to make them easier to review. Do you want me to merge the two patches?

Yes, I guess it will be the right idea to merge both patches otherwise you might see failing buildbots when both patches get merged at different times.

[sdesmalen]

Squashed the commit with the changes in D66935.

[efriedma]

LGTM

I was considering whether, instead of making getCalleeSavedStackSize approximate the stack size when running an individual pass, we should serialize it in the MIR. But this is probably okay as-is.

[omjavaid]

This corrects LLDB regressions.
LGTM.

[sdesmalen]

Thanks @efriedma and @omjavaid!

[thakis]

This breaks most bots on http://lab.llvm.org:8011/console . Unless this has a very quick fix, please revert and investigate asynchonously.

[sdesmalen]

In D68783#1717046, @thakis wrote:

This breaks most bots on http://lab.llvm.org:8011/console . Unless this has a very quick fix, please revert and investigate asynchonously.

Are you sure these are caused by this patch though? (Most bots that fail test more than this patch and I also can't quickly see how it causes all these failures)

[thakis]

In D68783#1717074, @sdesmalen wrote:

In D68783#1717046, @thakis wrote:

This breaks most bots on http://lab.llvm.org:8011/console . Unless this has a very quick fix, please revert and investigate asynchonously.

Are you sure these are caused by this patch though? (Most bots that fail test more than this patch and I also can't quickly see how it causes all these failures)

Yes, http://45.33.8.238/linux/2376/summary.html for example has just your change.

Maybe try reverting and if it doesn't help you know it's not your change. (It very likely is, though.)

[sdesmalen]

In D68783#1717082, @thakis wrote:

In D68783#1717074, @sdesmalen wrote:

In D68783#1717046, @thakis wrote:

This breaks most bots on http://lab.llvm.org:8011/console . Unless this has a very quick fix, please revert and investigate asynchonously.

Are you sure these are caused by this patch though? (Most bots that fail test more than this patch and I also can't quickly see how it causes all these failures)

Yes, http://45.33.8.238/linux/2376/summary.html for example has just your change.

Maybe try reverting and if it doesn't help you know it's not your change. (It very likely is, though.)

Got it! Thanks, I didn't quickly spot that one test from the console output. I'll revert the test and fix this separately. Thanks for pointing out!

llvm/lib/Target/AArch64/AArch64FrameLowering.cpp

 }
 
 static StackOffset getFPOffset(const MachineFunction &MF, int ObjectOffset) {
   const auto *AFI = MF.getInfo<AArch64FunctionInfo>();
   const auto &Subtarget = MF.getSubtarget<AArch64Subtarget>();
   bool IsWin64 =
       Subtarget.isCallingConvWin64(MF.getFunction().getCallingConv());
   unsigned FixedObject = IsWin64 ? alignTo(AFI->getVarArgsGPRSize(), 16) : 0;
-  unsigned FPAdjust = isTargetDarwin(MF) ? 16 : AFI->getCalleeSavedStackSize();
+  unsigned FPAdjust = isTargetDarwin(MF)
+                        ? 16 : AFI->getCalleeSavedStackSize(MF.getFrameInfo());
   return {ObjectOffset + FixedObject + FPAdjust, MVT::i8};
 }
 
 static StackOffset getStackOffset(const MachineFunction &MF, int ObjectOffset) {
   const auto &MFI = MF.getFrameInfo();
   return {ObjectOffset + (int)MFI.getStackSize(), MVT::i8};
 }
 
StackOffset AArch64FrameLowering::resolveFrameOffsetReference(
   const auto *RegInfo = static_cast<const AArch64RegisterInfo *>(
       MF.getSubtarget().getRegisterInfo());
   const auto *AFI = MF.getInfo<AArch64FunctionInfo>();
   const auto &Subtarget = MF.getSubtarget<AArch64Subtarget>();
 
   int FPOffset = getFPOffset(MF, ObjectOffset).getBytes();
   int Offset = getStackOffset(MF, ObjectOffset).getBytes();
   bool isCSR =
-      !isFixed && ObjectOffset >= -((int)AFI->getCalleeSavedStackSize());
+      !isFixed && ObjectOffset >= -((int)AFI->getCalleeSavedStackSize(MFI));
 
   const StackOffset &SVEStackSize = getSVEStackSize(MF);
   if (SVEStackSize)
     llvm_unreachable("Accessing frame indices in presence of SVE "
                      "not yet supported");
 
   // 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

llvm/lib/Target/AArch64/AArch64MachineFunctionInfo.h

class AArch64FunctionInfo final : public MachineFunctionInfo {
   /// determineCalleeSaves().
   bool HasStackFrame = false;
 
   /// Amount of stack frame size, not including callee-saved registers.
   unsigned LocalStackSize;
 
   /// Amount of stack frame size used for saving callee-saved registers.
   unsigned CalleeSavedStackSize;
+  bool HasCalleeSavedStackSize = false;
 
   /// Number of TLS accesses using the special (combinable)
   /// _TLS_MODULE_BASE_ symbol.
   unsigned NumLocalDynamicTLSAccesses = 0;
 
   /// FrameIndex for start of varargs area for arguments passed on the
   /// stack.
   int VarArgsStackIndex = 0;
public:
   }
 
   bool isSplitCSR() const { return IsSplitCSR; }
   void setIsSplitCSR(bool s) { IsSplitCSR = s; }
 
   void setLocalStackSize(unsigned Size) { LocalStackSize = Size; }
   unsigned getLocalStackSize() const { return LocalStackSize; }
 
-  void setCalleeSavedStackSize(unsigned Size) { CalleeSavedStackSize = Size; }
-  unsigned getCalleeSavedStackSize() const { return CalleeSavedStackSize; }
+  void setCalleeSavedStackSize(unsigned Size) {
+    CalleeSavedStackSize = Size;
+    HasCalleeSavedStackSize = true;
+  }
+
+  // When CalleeSavedStackSize has not been set (for example when
+  // some MachineIR pass is run in isolation), then recalculate
+  // the CalleeSavedStackSize directly from the CalleeSavedInfo.
+  // Note: This information can only be recalculated after PEI
+  // has assigned offsets to the callee save objects.
+  unsigned getCalleeSavedStackSize(const MachineFrameInfo &MFI) const {
+    bool ValidateCalleeSavedStackSize = false;
+
+#ifndef NDEBUG
+    // Make sure the calculated size derived from the CalleeSavedInfo
+    // equals the cached size that was calculated elsewhere (e.g. in
+    // determineCalleeSaves).
+    ValidateCalleeSavedStackSize = HasCalleeSavedStackSize;
+#endif
+
+    if (!HasCalleeSavedStackSize || ValidateCalleeSavedStackSize) {
+      assert(MFI.isCalleeSavedInfoValid() && "CalleeSavedInfo not calculated");
+      if (MFI.getCalleeSavedInfo().empty())
+        return 0;
+
+      int64_t MinOffset = std::numeric_limits<int64_t>::max();
+      int64_t MaxOffset = std::numeric_limits<int64_t>::min();
+      for (const auto &Info : MFI.getCalleeSavedInfo()) {
+        int FrameIdx = Info.getFrameIdx();
+        int64_t Offset = MFI.getObjectOffset(FrameIdx);
+        int64_t ObjSize = MFI.getObjectSize(FrameIdx);
+        MinOffset = std::min<int64_t>(Offset, MinOffset);
+        MaxOffset = std::max<int64_t>(Offset + ObjSize, MaxOffset);
+      }
+
+      unsigned Size = alignTo(MaxOffset - MinOffset, 16);
+      assert((!HasCalleeSavedStackSize || getCalleeSavedStackSize() == Size) &&
+             "Invalid size calculated for callee saves");
+      return Size;
+    }
+
+    return getCalleeSavedStackSize();
+  }
+
+  unsigned getCalleeSavedStackSize() const {
+    assert(HasCalleeSavedStackSize &&
+           "CalleeSavedStackSize has not been calculated");
+    return CalleeSavedStackSize;
+  }
 
   void incNumLocalDynamicTLSAccesses() { ++NumLocalDynamicTLSAccesses; }
   unsigned getNumLocalDynamicTLSAccesses() const {
     return NumLocalDynamicTLSAccesses;
   }
 
   Optional<bool> hasRedZone() const { return HasRedZone; }
   void setHasRedZone(bool s) { HasRedZone = s; }