AArch64: Fix frame record chain

The commit r369122 may keep LR and FP register (aka. frame record) in
the middle of a frame, thus we must add the offsets to ensure the FP
register always points to innermost frame record on the stack.

According to AAPCS64[1], a conforming code shall construct a linked list
of stack frames that can be traversed with frame records.  This commit
is also essential to frame-pointer-based stack unwinder (e.g.  the stack
unwinder in linx-perf-tools.)

[1] https://github.com/ARM-software/software-standards/blob/master/abi/aapcs64/aapcs64.rst#the-frame-pointer

Test: llvm-lit ${LLVM_SRC}/test/CodeGen/AArch64/framelayout-frame-record.ll
Test: llvm-lit ${LLVM_SRC}/test/CodeGen/AArch64

Differential Revision: https://reviews.llvm.org/D70800

1 files changed, 21 insertions, 16 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
index c732106014e..50d1c986948 100644
--- a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -832,10 +832,6 @@ static bool needsWinCFI(const MachineFunction &MF) {
          F.needsUnwindTableEntry();
 }
 
-static bool isTargetDarwin(const MachineFunction &MF) {
-  return MF.getSubtarget<AArch64Subtarget>().isTargetDarwin();
-}
-
 // Convenience function to determine whether I is an SVE callee save.
 bool IsSVECalleeSave(MachineBasicBlock::iterator I) {
   switch (I->getOpcode()) {
@@ -1016,7 +1012,7 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
 
   if (HasFP) {
     // Only set up FP if we actually need to.
-    int64_t FPOffset = isTargetDarwin(MF) ? (AFI->getCalleeSavedStackSize() - 16) : 0;
+    int64_t FPOffset = AFI->getCalleeSaveBaseToFrameRecordOffset();
 
     if (CombineSPBump)
       FPOffset += AFI->getLocalStackSize();
@@ -1229,11 +1225,6 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
   }
 
   if (needsFrameMoves) {
-    const DataLayout &TD = MF.getDataLayout();
-    const int StackGrowth = isTargetDarwin(MF)
-                                ? (2 * -TD.getPointerSize(0))
-                                : -AFI->getCalleeSavedStackSize();
-    Register FramePtr = RegInfo->getFrameRegister(MF);
     // An example of the prologue:
     //
     //     .globl __foo
@@ -1301,10 +1292,15 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
     //     .cfi_offset w28, -32
 
     if (HasFP) {
+      const int OffsetToFirstCalleeSaveFromFP =
+          AFI->getCalleeSaveBaseToFrameRecordOffset() -
+          AFI->getCalleeSavedStackSize();
+      Register FramePtr = RegInfo->getFrameRegister(MF);
+
       // Define the current CFA rule to use the provided FP.
       unsigned Reg = RegInfo->getDwarfRegNum(FramePtr, true);
       unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createDefCfa(
-          nullptr, Reg, StackGrowth - FixedObject));
+          nullptr, Reg, OffsetToFirstCalleeSaveFromFP - FixedObject));
       BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
           .addCFIIndex(CFIIndex)
           .setMIFlags(MachineInstr::FrameSetup);
@@ -1611,10 +1607,8 @@ void AArch64FrameLowering::emitEpilogue(MachineFunction &MF,
   // non-post-indexed loads for the restores if we aren't actually going to
   // be able to save any instructions.
   if (!IsFunclet && (MFI.hasVarSizedObjects() || AFI->isStackRealigned())) {
-    int64_t OffsetToFrameRecord =
-        isTargetDarwin(MF) ? (-(int64_t)AFI->getCalleeSavedStackSize() + 16) : 0;
     emitFrameOffset(MBB, LastPopI, DL, AArch64::SP, AArch64::FP,
-                    {OffsetToFrameRecord, MVT::i8},
+                    {-AFI->getCalleeSaveBaseToFrameRecordOffset(), MVT::i8},
                     TII, MachineInstr::FrameDestroy, false, NeedsWinCFI);
   } else if (NumBytes)
     emitFrameOffset(MBB, LastPopI, DL, AArch64::SP, AArch64::SP,
@@ -1676,8 +1670,8 @@ static StackOffset getFPOffset(const MachineFunction &MF, int64_t ObjectOffset)
   bool IsWin64 =
       Subtarget.isCallingConvWin64(MF.getFunction().getCallingConv());
   unsigned FixedObject = IsWin64 ? alignTo(AFI->getVarArgsGPRSize(), 16) : 0;
-  unsigned FPAdjust = isTargetDarwin(MF)
-                        ? 16 : AFI->getCalleeSavedStackSize(MF.getFrameInfo());
+  unsigned FPAdjust = AFI->getCalleeSavedStackSize(MF.getFrameInfo()) -
+                      AFI->getCalleeSaveBaseToFrameRecordOffset();
   return {ObjectOffset + FixedObject + FPAdjust, MVT::i8};
 }
 
@@ -1934,6 +1928,9 @@ static void computeCalleeSaveRegisterPairs(
   if (CSI.empty())
     return;
 
+  const bool IsTargetWindows =
+      MF.getSubtarget<AArch64Subtarget>().isTargetWindows();
+
   bool NeedsWinCFI = needsWinCFI(MF);
   AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
   MachineFrameInfo &MFI = MF.getFrameInfo();
@@ -2058,6 +2055,14 @@ static void computeCalleeSaveRegisterPairs(
             (RPI.isScalable() && RPI.Offset >= -256 && RPI.Offset <= 255)) &&
            "Offset out of bounds for LDP/STP immediate");
 
+    // Save the offset to frame record so that the FP register can point to the
+    // innermost frame record (spilled FP and LR registers).
+    if (NeedsFrameRecord && ((!IsTargetWindows && RPI.Reg1 == AArch64::LR &&
+                              RPI.Reg2 == AArch64::FP) ||
+                             (IsTargetWindows && RPI.Reg1 == AArch64::FP &&
+                              RPI.Reg2 == AArch64::LR)))
+      AFI->setCalleeSaveBaseToFrameRecordOffset(Offset);
+
     RegPairs.push_back(RPI);
     if (RPI.isPaired())
       ++i;