[win][x64] SetFrame does not count as a stack alloc for unwind v2

[dpaoliello]

No description provided.

[llvmbot]

@llvm/pr-subscribers-backend-x86

Author: Daniel Paoliello (dpaoliello)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/154235.diff

2 Files Affected:

• (modified) llvm/lib/Target/X86/X86WinEHUnwindV2.cpp (+4-5)
• (modified) llvm/test/CodeGen/X86/win64-eh-unwindv2.ll (+19)

diff --git a/llvm/lib/Target/X86/X86WinEHUnwindV2.cpp b/llvm/lib/Target/X86/X86WinEHUnwindV2.cpp
index ea8b88f41bb87..0edff5333a36b 100644
--- a/llvm/lib/Target/X86/X86WinEHUnwindV2.cpp
+++ b/llvm/lib/Target/X86/X86WinEHUnwindV2.cpp
@@ -130,12 +130,10 @@ bool X86WinEHUnwindV2::runOnMachineFunction(MachineFunction &MF) {
         break;
 
       case X86::SEH_StackAlloc:
-      case X86::SEH_SetFrame:
         if (State != FunctionState::InProlog)
-          llvm_unreachable("SEH_StackAlloc or SEH_SetFrame outside of prolog");
+          llvm_unreachable("SEH_StackAlloc outside of prolog");
         // Assume a large alloc...
-        ApproximatePrologCodeCount +=
-            (MI.getOpcode() == X86::SEH_StackAlloc) ? 3 : 1;
+        ApproximatePrologCodeCount += 3;
         HasStackAlloc = true;
         break;
 
@@ -147,9 +145,10 @@ bool X86WinEHUnwindV2::runOnMachineFunction(MachineFunction &MF) {
         ApproximatePrologCodeCount += 3;
         break;
 
+      case X86::SEH_SetFrame:
       case X86::SEH_PushFrame:
         if (State != FunctionState::InProlog)
-          llvm_unreachable("SEH_PushFrame outside of prolog");
+          llvm_unreachable("SEH_SetFrame or SEH_PushFrame outside of prolog");
         ApproximatePrologCodeCount++;
         break;
 
diff --git a/llvm/test/CodeGen/X86/win64-eh-unwindv2.ll b/llvm/test/CodeGen/X86/win64-eh-unwindv2.ll
index 326127a919f3a..2629b887d3228 100644
--- a/llvm/test/CodeGen/X86/win64-eh-unwindv2.ll
+++ b/llvm/test/CodeGen/X86/win64-eh-unwindv2.ll
@@ -171,6 +171,25 @@ define dso_local void @large_aligned_alloc() align 16 {
 ; CHECK-NEXT:   retq
 ; CHECK-NEXT:   .seh_endproc
 
+define dso_local void @set_frame_only() local_unnamed_addr {
+  tail call i64 @llvm.x86.flags.read.u64()
+  ret void
+}
+
+; CHECK-LABEL:  set_frame_only:
+; CHECK:        .seh_unwindversion 2
+; CHECK:        .seh_pushreg %rbp
+; CHECK:        .seh_setframe %rbp, 0
+; CHECK:        .seh_endprologue
+; CHECK-NOT:    .seh_endproc
+; CHECK:        .seh_startepilogue
+; CHECK-NEXT:   .seh_unwindv2start
+; CHECK-NEXT:   popq    %rbp
+; CHECK-NEXT:   .seh_endepilogue
+; CHECK-NEXT:   retq
+; CHECK-NEXT:   .seh_endproc
+
+declare i64 @llvm.x86.flags.read.u64()
 declare void @a() local_unnamed_addr
 declare i32 @b() local_unnamed_addr
 declare i32 @c(i32) local_unnamed_addr

[dpaoliello]

Still working on this... scope has expanded.

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff HEAD~1 HEAD --extensions cpp -- llvm/lib/MC/MCWin64EH.cpp llvm/lib/Target/X86/X86WinEHUnwindV2.cpp

View the diff from clang-format here.

diff --git a/llvm/lib/MC/MCWin64EH.cpp b/llvm/lib/MC/MCWin64EH.cpp
index 2638b9528..c198ecb71 100644
--- a/llvm/lib/MC/MCWin64EH.cpp
+++ b/llvm/lib/MC/MCWin64EH.cpp
@@ -40,10 +40,9 @@ public:
   static MCUnwindV2EpilogTargetExpr *
   create(const WinEH::FrameInfo &FrameInfo,
          const WinEH::FrameInfo::Epilog &Epilog, uint8_t EpilogSize_,
-         StringRef FunctionName_,
-         MCContext &Ctx) {
+         StringRef FunctionName_, MCContext &Ctx) {
     return new (Ctx) MCUnwindV2EpilogTargetExpr(FrameInfo, Epilog, EpilogSize_,
-                                                 FunctionName_);
+                                                FunctionName_);
   }
 
   void printImpl(raw_ostream &OS, const MCAsmInfo *MAI) const override {
@@ -339,8 +338,8 @@ static void EmitUnwindInfo(MCStreamer &streamer, WinEH::FrameInfo *info) {
       // Each epilog is emitted as a fixup, since we can't measure the distance
       // between the start of the epilog and the end of the function until
       // layout has been completed.
-      auto *MCE = MCUnwindV2EpilogTargetExpr::create(*info, Epilog.second,
-                                                     EpilogSize, info->Function->getName(), context);
+      auto *MCE = MCUnwindV2EpilogTargetExpr::create(
+          *info, Epilog.second, EpilogSize, info->Function->getName(), context);
       OS->addFixup(MCE, FK_Data_2);
       OS->appendContents(2, 0);
     }
@@ -386,7 +385,8 @@ bool MCUnwindV2EpilogTargetExpr::evaluateAsRelocatableImpl(
   auto Offset = GetOptionalAbsDifference(*Asm, FunctionEnd, UnwindV2Start);
   if (!Offset) {
     Asm->getContext().reportError(
-        Loc, "Failed to evaluate epilog offset for Unwind v2 in " + FunctionName);
+        Loc,
+        "Failed to evaluate epilog offset for Unwind v2 in " + FunctionName);
     return false;
   }
   assert(*Offset > 0);
@@ -394,8 +394,9 @@ bool MCUnwindV2EpilogTargetExpr::evaluateAsRelocatableImpl(
   if (*Offset > MaxEpilogOffset) {
     dbgs() << "Unwindv2: " << UnwindV2Start->getSection().getName();
     dbgs() << "FunctionEnd: " << FunctionEnd->getSection().getName();
-    Asm->getContext().reportError(Loc,
-                                  "Epilog offset is too large (0x" + Twine::utohexstr(*Offset) + ") for Unwind v2 in " + FunctionName);
+    Asm->getContext().reportError(
+        Loc, "Epilog offset is too large (0x" + Twine::utohexstr(*Offset) +
+                 ") for Unwind v2 in " + FunctionName);
     return false;
   }