[ARM64][Windows] Fix local stack size for funclets

The comment was misplaced, and the code didn't do what the comment indicated,
namely ignoring the varargs portion when computing the local stack size of a
funclet in emitEpilogue.  This results in incorrect offset computations within
funclets that are contained in vararg functions.

Differential Revision: https://reviews.llvm.org/D55096

llvm-svn: 348222

llvm/lib/Target/AArch64/AArch64FrameLowering.cpp

@@ -1289,12 +1289,17 @@ void AArch64FrameLowering::emitEpilogue(MachineFunction &MF,
 
   bool IsWin64 =
       Subtarget.isCallingConvWin64(MF.getFunction().getCallingConv());
-  unsigned FixedObject = IsWin64 ? alignTo(AFI->getVarArgsGPRSize(), 16) : 0;
+  // Var args are accounted for in the containing function, so don't
+  // include them for funclets.
+  unsigned FixedObject =
+      (IsWin64 && !IsFunclet) ? alignTo(AFI->getVarArgsGPRSize(), 16) : 0;
 
   uint64_t AfterCSRPopSize = ArgumentPopSize;
   auto PrologueSaveSize = AFI->getCalleeSavedStackSize() + FixedObject;
-  // Var args are accounted for in the containting function, so don't
-  // include them for funclets.
+  // We cannot rely on the local stack size set in emitPrologue if the function
+  // has funclets, as funclets have different local stack size requirements, and
+  // the current value set in emitPrologue may be that of the containing
+  // function.
   if (MF.hasEHFunclets())
     AFI->setLocalStackSize(NumBytes - PrologueSaveSize);
   bool CombineSPBump = shouldCombineCSRLocalStackBump(MF, NumBytes);

llvm/test/CodeGen/AArch64/funclet-local-stack-size.ll

@@ -0,0 +1,53 @@
+; RUN: llc -o - %s -mtriple=aarch64-windows | FileCheck %s
+; Check that the local stack size is computed correctly for a funclet contained
+; within a varargs function.  The varargs component shouldn't be included in the
+; local stack size computation.
+target datalayout = "e-m:w-p:64:64-i32:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-unknown-windows-msvc19.11.0"
+
+%rtti.TypeDescriptor2 = type { i8**, i8*, [3 x i8] }
+
+$"??_R0H@8" = comdat any
+
+@"??_7type_info@@6B@" = external constant i8*
+@"??_R0H@8" = linkonce_odr global %rtti.TypeDescriptor2 { i8** @"??_7type_info@@6B@", i8* null, [3 x i8] c".H\00" }, comdat
+
+; CHECK-LABEL: ?catch$2@?0??func@@YAHHHZZ@4HA
+; CHECK: stp x29, x30, [sp, #-16]!
+; CHECK: ldp x29, x30, [sp], #16
+; Function Attrs: uwtable
+define dso_local i32 @"?func@@YAHHHZZ"(i32 %a, i32, ...) local_unnamed_addr #0 personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) {
+entry:
+  %arr = alloca [10 x i32], align 4
+  %a2 = alloca i32, align 4
+  %1 = bitcast [10 x i32]* %arr to i8*
+  %arraydecay = getelementptr inbounds [10 x i32], [10 x i32]* %arr, i64 0, i64 0
+  %call = call i32 @"?init@@YAHPEAH@Z"(i32* nonnull %arraydecay)
+  %call1 = invoke i32 @"?func2@@YAHXZ"()
+          to label %cleanup unwind label %catch.dispatch
+
+catch.dispatch:                                   ; preds = %entry
+  %2 = catchswitch within none [label %catch] unwind to caller
+
+catch:                                            ; preds = %catch.dispatch
+  %3 = catchpad within %2 [%rtti.TypeDescriptor2* @"??_R0H@8", i32 0, i32* %a2]
+  %4 = load i32, i32* %a2, align 4
+  %add = add nsw i32 %4, 1
+  catchret from %3 to label %cleanup
+
+cleanup:                                          ; preds = %entry, %catch
+  %retval.0 = phi i32 [ %add, %catch ], [ %call1, %entry ]
+  ret i32 %retval.0
+}
+
+declare dso_local i32 @"?init@@YAHPEAH@Z"(i32*)
+
+declare dso_local i32 @"?func2@@YAHXZ"()
+
+declare dso_local i32 @__CxxFrameHandler3(...)
+
+attributes #0 = { uwtable }
+
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 1, !"wchar_size", i32 2}