[AArch64] Fix mismatch in prologue and epilogue for funclets on Windows

The generated code for a funclet can have an add to sp in the epilogue
for which there is no corresponding sub in the prologue.

This patch removes the early return from emitPrologue that was
preventing the sub to sp, and instead conditionalizes the appropriate
parts of the rest of the function.

Fixes https://bugs.llvm.org/show_bug.cgi?id=45345

Differential Revision: https://reviews.llvm.org/D77015

llvm/lib/Target/AArch64/AArch64FrameLowering.cpp

@@ -1029,32 +1029,8 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
     ++MBBI;
   }
 
-  // The code below is not applicable to funclets. We have emitted all the SEH
-  // opcodes that we needed to emit.  The FP and BP belong to the containing
-  // function.
-  if (IsFunclet) {
-    if (NeedsWinCFI) {
-      HasWinCFI = true;
-      BuildMI(MBB, MBBI, DL, TII->get(AArch64::SEH_PrologEnd))
-          .setMIFlag(MachineInstr::FrameSetup);
-    }
-
-    // SEH funclets are passed the frame pointer in X1.  If the parent
-    // function uses the base register, then the base register is used
-    // directly, and is not retrieved from X1.
-    if (F.hasPersonalityFn()) {
-      EHPersonality Per = classifyEHPersonality(F.getPersonalityFn());
-      if (isAsynchronousEHPersonality(Per)) {
-        BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::COPY), AArch64::FP)
-            .addReg(AArch64::X1).setMIFlag(MachineInstr::FrameSetup);
-        MBB.addLiveIn(AArch64::X1);
-      }
-    }
-
-    return;
-  }
-
-  if (HasFP) {
+  // For funclets the FP belongs to the containing function.
+  if (!IsFunclet && HasFP) {
     // Only set up FP if we actually need to.
     int64_t FPOffset = isTargetDarwin(MF) ? (AFI->getCalleeSavedStackSize() - 16) : 0;
 
@@ -1197,7 +1173,9 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
 
   // Allocate space for the rest of the frame.
   if (NumBytes) {
-    const bool NeedsRealignment = RegInfo->needsStackRealignment(MF);
+    // Alignment is required for the parent frame, not the funclet
+    const bool NeedsRealignment =
+        !IsFunclet && RegInfo->needsStackRealignment(MF);
     unsigned scratchSPReg = AArch64::SP;
 
     if (NeedsRealignment) {
@@ -1250,7 +1228,8 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
   // FIXME: Clarify FrameSetup flags here.
   // Note: Use emitFrameOffset() like above for FP if the FrameSetup flag is
   // needed.
-  if (RegInfo->hasBasePointer(MF)) {
+  // For funclets the BP belongs to the containing function.
+  if (!IsFunclet && RegInfo->hasBasePointer(MF)) {
     TII->copyPhysReg(MBB, MBBI, DL, RegInfo->getBaseRegister(), AArch64::SP,
                      false);
     if (NeedsWinCFI) {
@@ -1267,6 +1246,19 @@ void AArch64FrameLowering::emitPrologue(MachineFunction &MF,
         .setMIFlag(MachineInstr::FrameSetup);
   }
 
+  // SEH funclets are passed the frame pointer in X1.  If the parent
+  // function uses the base register, then the base register is used
+  // directly, and is not retrieved from X1.
+  if (IsFunclet && F.hasPersonalityFn()) {
+    EHPersonality Per = classifyEHPersonality(F.getPersonalityFn());
+    if (isAsynchronousEHPersonality(Per)) {
+      BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::COPY), AArch64::FP)
+          .addReg(AArch64::X1)
+          .setMIFlag(MachineInstr::FrameSetup);
+      MBB.addLiveIn(AArch64::X1);
+    }
+  }
+
   if (needsFrameMoves) {
     const DataLayout &TD = MF.getDataLayout();
     const int StackGrowth = isTargetDarwin(MF)

llvm/test/CodeGen/AArch64/funclet-match-add-sub-stack.ll

@@ -0,0 +1,62 @@
+; RUN: llc -o - %s -mtriple=aarch64-windows | FileCheck %s
+; Check that the stack bump around a funclet is computed correctly in both the
+; prologue and epilogue in the case we have a MaxCallFrameSize > 0 and are doing alloca
+target datalayout = "e-m:w-p:64:64-i32:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-pc-windows-msvc19.25.28611"
+
+; // requires passing arguments on the stack
+; void test2(void*, int, int, int, int, int, int, int, int);
+;
+; // function with the funclet being checked
+; void test1(size_t bytes)
+; {
+;   // alloca forces a separate callee save bump and stack bump
+;   void *data = _alloca(bytes);
+;   try {
+;     test2(data, 0, 1, 2, 3, 4, 5, 6, 7);
+;   } catch (...) {
+;     // the funclet being checked
+;   }
+; }
+
+; CHECK-LABEL: ?catch$2@?0??test1@@YAX_K@Z@4HA
+; CHECK: sub sp, sp, #16
+; CHECK: add sp, sp, #16
+; Function Attrs: uwtable
+define dso_local void @"?test1@@YAX_K@Z"(i64 %0) #0 personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) {
+  %2 = alloca i64, align 8
+  %3 = alloca i8*, align 8
+  store i64 %0, i64* %2, align 8
+  %4 = load i64, i64* %2, align 8
+  %5 = alloca i8, i64 %4, align 16
+  store i8* %5, i8** %3, align 8
+  %6 = load i8*, i8** %3, align 8
+  invoke void @"?test2@@YAXPEAXHHHHHHHH@Z"(i8* %6, i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7)
+          to label %13 unwind label %7
+
+7:                                                ; preds = %1
+  %8 = catchswitch within none [label %9] unwind to caller
+
+9:                                                ; preds = %7
+  %10 = catchpad within %8 [i8* null, i32 64, i8* null]
+  catchret from %10 to label %11
+
+11:                                               ; preds = %9
+  br label %12
+
+12:                                               ; preds = %11, %13
+  ret void
+
+13:                                               ; preds = %1
+  br label %12
+}
+
+declare dso_local void @"?test2@@YAXPEAXHHHHHHHH@Z"(i8*, i32, i32, i32, i32, i32, i32, i32, i32) #1
+
+declare dso_local i32 @__CxxFrameHandler3(...)
+
+attributes #0 = { uwtable }
+
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 1, !"wchar_size", i32 2}