[llvm] 4b11f90 - [RISCV] Fix missing stack pointer recover

[Kito Cheng via llvm-commits]

Author: Kito Cheng
Date: 2022-06-09T23:38:50+08:00
New Revision: 4b11f909030a9831e4dded93068f224bec0fe296

URL: https://github.com/llvm/llvm-project/commit/4b11f909030a9831e4dded93068f224bec0fe296
DIFF: https://github.com/llvm/llvm-project/commit/4b11f909030a9831e4dded93068f224bec0fe296.diff

LOG: [RISCV] Fix missing stack pointer recover

In order to make sure the stack point is right through the EH region,
we also need to restore stack pointer from the frame pointer if we
don't preserve stack space within prologue/epilogue for outgoing variables,
normally it's just checking the variable sized object is present or not
is enough, but we also don't preserve that at prologue/epilogue when
have vector objects in stack.

Example to show what happened:
```
try {
  sp adjust for outgoing args. // 1. Sp changed.
  func_call  // 2. Exception raised
  sp restore // Oh, not restored
} catch {
  // 3. And now we are here.
}

// 4. Prepare to return!, restore return address from stack, but...sp is wrong.
// 5. Screw up!
```

Reviewed By: rogfer01

Differential Revision: https://reviews.llvm.org/D126861

Added: 
    

Modified: 
    llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
    llvm/test/CodeGen/RISCV/miss-sp-restore-eh.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp b/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
index 582a4a9796e5..945246f6ce0b 100644
--- a/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
@@ -637,7 +637,15 @@ void RISCVFrameLowering::emitEpilogue(MachineFunction &MF,
   // Restore the stack pointer using the value of the frame pointer. Only
   // necessary if the stack pointer was modified, meaning the stack size is
   // unknown.
-  if (RI->hasStackRealignment(MF) || MFI.hasVarSizedObjects()) {
+  //
+  // In order to make sure the stack point is right through the EH region,
+  // we also need to restore stack pointer from the frame pointer if we
+  // don't preserve stack space within prologue/epilogue for outgoing variables,
+  // normally it's just checking the variable sized object is present or not
+  // is enough, but we also don't preserve that at prologue/epilogue when
+  // have vector objects in stack.
+  if (RI->hasStackRealignment(MF) || MFI.hasVarSizedObjects() ||
+      !hasReservedCallFrame(MF)) {
     assert(hasFP(MF) && "frame pointer should not have been eliminated");
     adjustReg(MBB, LastFrameDestroy, DL, SPReg, FPReg, -FPOffset,
               MachineInstr::FrameDestroy);

diff  --git a/llvm/test/CodeGen/RISCV/miss-sp-restore-eh.ll b/llvm/test/CodeGen/RISCV/miss-sp-restore-eh.ll
index 2bba9cee2fee..b7c0a9f29273 100644
--- a/llvm/test/CodeGen/RISCV/miss-sp-restore-eh.ll
+++ b/llvm/test/CodeGen/RISCV/miss-sp-restore-eh.ll
@@ -48,6 +48,7 @@ define signext i32 @foo() #1 personality ptr @__gxx_personality_v0 {
 ; CHECK-NEXT:    lw s1, 0(a0)
 ; CHECK-NEXT:    call __cxa_end_catch at plt
 ; CHECK-NEXT:    mv a0, s1
+; CHECK-NEXT:    addi sp, s0, -32
 ; CHECK-NEXT:    ld ra, 24(sp) # 8-byte Folded Reload
 ; CHECK-NEXT:    ld s0, 16(sp) # 8-byte Folded Reload
 ; CHECK-NEXT:    ld s1, 8(sp) # 8-byte Folded Reload