Work around an MSVC2017 update 3 codegen bug.

[thakis]

Summary

MSVC2017 update 3 produces a clang that crashes when compiling clang. Disabling optimizations for StmtProfiler::VisitCXXOperatorCallExpr() makes the crash go away.

Patch from Bruce Dawson <[e-mail]>!

[smeenai]

lib/AST/StmtProfile.cpp

1367

Is it worth using _MSC_FULL_VER to limit this to Update 3 specifically?

[thakis]

From what I understand, _MSC_VER changes with each 2017 update.

[rnk]

lgtm

[thakis]

r308897.

lib/AST/StmtProfile.cpp

static Stmt::StmtClass DecodeOperatorCall(const CXXOperatorCallExpr *S,
       
   case OO_Subscript:
     return Stmt::ArraySubscriptExprClass;
   }
   
   llvm_unreachable("Invalid overloaded operator expression");
 }
 
+#if defined(_MSC_VER) && _MSC_VER == 1911
+// Work around https://developercommunity.visualstudio.com/content/problem/84002/clang-cl-when-built-with-vc-2017-crashes-cause-vc.html
+// MSVC 2017 update 3 miscompiles this function, and a clang built with it
+// will crash in stage 2 of a bootstrap build.
+#pragma optimize("", off)
+#endif
+
 void StmtProfiler::VisitCXXOperatorCallExpr(const CXXOperatorCallExpr *S) {
   if (S->isTypeDependent()) {
     // Type-dependent operator calls are profiled like their underlying
     // syntactic operator.
     //
     // An operator call to operator-> is always implicit, so just skip it. The
     // enclosing MemberExpr will profile the actual member access.
     if (S->getOperator() == OO_Arrow)
if (S->isTypeDependent()) {
 
     return;
   }
 
   VisitCallExpr(S);
   ID.AddInteger(S->getOperator());
 }
 
+#if defined(_MSC_VER) && _MSC_VER == 1911
+#pragma optimize("", on)
+#endif
+
 void StmtProfiler::VisitCXXMemberCallExpr(const CXXMemberCallExpr *S) {
   VisitCallExpr(S);
 }
 
 void StmtProfiler::VisitCUDAKernelCallExpr(const CUDAKernelCallExpr *S) {
   VisitCallExpr(S);
 }