[WinEH] Only generate UnwindHelp slot for MSVCXX

[JosephTremoulet]

Summary

Other personalities don't use this special frame slot.

[rnk]

lgtm

lib/Target/X86/X86ISelLowering.cpp

if (!Is64Bit) {
     if (CallConv == CallingConv::X86_FastCall ||
         CallConv == CallingConv::X86_ThisCall)
       // fastcc functions can't have varargs.
       FuncInfo->setVarArgsFrameIndex(0xAAAAAAA);
   }
 
   FuncInfo->setArgumentStackSize(StackSize);
 
-  if (MMI.hasWinEHFuncInfo(Fn)) {
-    if (Is64Bit) {
-      int UnwindHelpFI = MFI->CreateStackObject(8, 8, /*isSS=*/false);
-      SDValue StackSlot = DAG.getFrameIndex(UnwindHelpFI, MVT::i64);
-      MMI.getWinEHFuncInfo(MF.getFunction()).UnwindHelpFrameIdx = UnwindHelpFI;
-      SDValue Neg2 = DAG.getConstant(-2, dl, MVT::i64);
-      Chain = DAG.getStore(Chain, dl, Neg2, StackSlot,
-                           MachinePointerInfo::getFixedStack(
-                               DAG.getMachineFunction(), UnwindHelpFI),
-                           /*isVolatile=*/true,
-                           /*isNonTemporal=*/false, /*Alignment=*/0);
-    }
-  }
+  if (MMI.hasWinEHFuncInfo(Fn) && Is64Bit &&
+      classifyEHPersonality(Fn->getPersonalityFn()) ==
+          EHPersonality::MSVC_CXX) {
 
   return Chain;
 }
 
 SDValue
 X86TargetLowering::LowerMemOpCallTo(SDValue Chain,
                                     SDValue StackPtr, SDValue Arg,
                                     SDLoc dl, SelectionDAG &DAG,

test/CodeGen/X86/seh-catchpad.ll

ehcleanup.end:                                    ; preds = %ehcleanup
   cleanupendpad %1 unwind label %catch.dispatch.7
 }
 
 ; CHECK: main:                                   # @main
 ; CHECK: .seh_proc main
 ; CHECK:         .seh_handler __C_specific_handler, @unwind, @except
 ; CHECK:         pushq   %rbp
 ; CHECK:         .seh_pushreg 5
-; CHECK:         subq    $48, %rsp
-; CHECK:         .seh_stackalloc 48
-; CHECK:         leaq    48(%rsp), %rbp
-; CHECK:         .seh_setframe 5, 48
+; CHECK:         subq    $32, %rsp
+; CHECK:         .seh_stackalloc 32
+; CHECK:         leaq    32(%rsp), %rbp
+; CHECK:         .seh_setframe 5, 32
 ; CHECK:         .seh_endprologue
 ; CHECK: .Ltmp0:
 ; CHECK:         movl    $1, %ecx
 ; CHECK:         xorl    %edx, %edx
 ; CHECK:         callq   do_div
 ; CHECK: .Ltmp1:
 ; CHECK: .LBB1_[[epilogue:[0-9]+]]:                                # %__try.cont.12
 ; CHECK:         xorl    %eax, %eax
-; CHECK:         addq    $48, %rsp
+; CHECK:         addq    $32, %rsp
 ; CHECK:         popq    %rbp
 ; CHECK:         retq
 ; CHECK: .LBB1_[[except1bb:[0-9]+]]:                                # %catch.dispatch
 ; CHECK: .Ltmp2:
 ; CHECK:         movl    $1, %ecx
 ; CHECK:         xorl    %edx, %edx
 ; CHECK:         callq   do_div
 ; CHECK: .Ltmp3:

 ; CHECK: .seh_proc "?dtor$3@?0?main@4HA"
 ; CHECK:         .seh_handler __C_specific_handler, @unwind, @except
 ; CHECK: .LBB1_[[finbb]]:                                # %ehcleanup
 ; CHECK:         movq    %rdx, 16(%rsp)
 ; CHECK:         pushq   %rbp
 ; CHECK:         .seh_pushreg 5
 ; CHECK:         subq    $32, %rsp
 ; CHECK:         .seh_stackalloc 32
-; CHECK:         leaq    48(%rdx), %rbp
+; CHECK:         leaq    32(%rdx), %rbp
 ; CHECK:         .seh_endprologue
 ; CHECK:         callq   "?fin$0@0@main@@"
 ; CHECK:         nop
 ; CHECK:         addq    $32, %rsp
 ; CHECK:         popq    %rbp
 ; CHECK:         retq
 ; CHECK:         .seh_handlerdata
 ; CHECK:         .seh_endproc