[WinEH] Don't emit state stores or EH thunks for available_externally functions

The exception handler thunk needs to reference the LSDA of the parent
function, which won't be emitted if it's available_externally.

Fixes PR35736. ThinLTO ends up producing available_externally functions
that use _CxxFrameHandler3.

llvm-svn: 321532

lib/Target/X86/X86WinEHState.cpp

@@ -149,6 +149,12 @@ void WinEHStatePass::getAnalysisUsage(AnalysisUsage &AU) const {
 }
 
 bool WinEHStatePass::runOnFunction(Function &F) {
+  // Don't insert state stores or exception handler thunks for
+  // available_externally functions. The handler needs to reference the LSDA,
+  // which will not be emitted in this case.
+  if (F.hasAvailableExternallyLinkage())
+    return false;
+
   // Check the personality. Do nothing if this personality doesn't use funclets.
   if (!F.hasPersonalityFn())
     return false;

test/CodeGen/X86/win32-eh-available-externally.ll

@@ -0,0 +1,28 @@
+; RUN: opt -S -x86-winehstate < %s | FileCheck %s --check-prefix=IR
+; RUN: llc < %s | FileCheck %s --check-prefix=ASM
+
+; IR-NOT: define.*__ehhandler
+; IR: define available_externally void @foo(void ()*)
+; IR-NOT: define.*__ehhandler
+
+; No code should be emitted.
+; ASM-NOT: __ehtable
+; ASM-NOT: __ehhandler
+
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
+target triple = "i686-pc-windows-msvc"
+
+declare i32 @__CxxFrameHandler3(...) unnamed_addr
+
+define available_externally void @foo(void ()*) personality i32 (...)* @__CxxFrameHandler3 {
+start:
+  invoke void %0()
+          to label %good unwind label %bad
+
+good:                                             ; preds = %start
+  ret void
+
+bad:                                              ; preds = %start
+  %cleanuppad = cleanuppad within none []
+  cleanupret from %cleanuppad unwind to caller
+}