Fix an issue where backend crashes after frontend emits an error message

[manmanren]

Summary

It can happen that frontend emits error message when releasing the builder. When that happens, we emit the error message and continue to invoke backend.
Backend will then crash.

The fix is quite simple, we check for errors after releasing the builder.

[ahatanak]

lib/CodeGen/ModuleBuilder.cpp

214

Is it possible to avoid the code duplication if the condition is inverted as shown below?

if (!Diags.hasErrorOccurred())

// call Builder->Release()

if (!Diags.hasErrorOccurred())

return;

// Clear Builder and reset M

[manmanren]

Addressing comments from Akira and Justin.

[echristo]

Seems like a weird place to handle this, but it's been there for a long time. That said, I see how we can get there now, thanks!

-eric

lib/CodeGen/ModuleBuilder.cpp

void HandleTagDeclRequiredDefinition(const TagDecl *D) override {
         return;
 
       if (CodeGen::CGDebugInfo *DI = Builder->getModuleDebugInfo())
         if (const RecordDecl *RD = dyn_cast<RecordDecl>(D))
           DI->completeRequiredType(RD);
     }
 
     void HandleTranslationUnit(ASTContext &Ctx) override {
+      // Release the Builder when there is no error.
+      if (!Diags.hasErrorOccurred() && Builder)
+        Builder->Release();
+
+      // If there are errors before or when releasing the Builder, reset
+      // the module to stop here before invoking the backend.
       if (Diags.hasErrorOccurred()) {
         if (Builder)
           Builder->clear();
         M.reset();
         return;
       }
-
-      if (Builder)
-        Builder->Release();
     }
 
     void CompleteTentativeDefinition(VarDecl *D) override {
       if (Diags.hasErrorOccurred())
         return;
 
       Builder->EmitTentativeDefinition(D);
     }
 

test/CodeGen/target-builtin-error-3.c

+// RUN: %clang_cc1 %s -triple=x86_64-apple-darwin -S -verify -o - -target-feature +avx
+
+// RUN: not %clang_cc1 %s -triple=x86_64-apple-darwin -emit-obj -target-feature +avx 2> %t.err
+// RUN: FileCheck < %t.err %s
+// CHECK: 1 error generated
+
+typedef unsigned short uint16_t;
+typedef long long __m128i __attribute__((__vector_size__(16)));
+typedef float __v8sf __attribute__ ((__vector_size__ (32)));
+typedef float __m256 __attribute__ ((__vector_size__ (32)));
+typedef uint16_t half;
+typedef __attribute__ ((ext_vector_type( 8),__aligned__( 16))) half half8;
+typedef __attribute__ ((ext_vector_type(16),__aligned__( 32))) half half16;
+typedef __attribute__ ((ext_vector_type(16),__aligned__( 2))) half half16U;
+typedef __attribute__ ((ext_vector_type( 8),__aligned__( 32))) float float8;
+typedef __attribute__ ((ext_vector_type(16),__aligned__( 64))) float float16;
+static inline half8 __attribute__((__overloadable__)) convert_half( float8 a ) {
+  return __extension__ ({ __m256 __a = (a); (__m128i)__builtin_ia32_vcvtps2ph256((__v8sf)__a, (0x00)); }); // expected-error {{'__builtin_ia32_vcvtps2ph256' needs target feature f16c}}
+}
+static inline half16 __attribute__((__overloadable__)) convert_half( float16 a ) {
+  half16 r; 
+  r.lo = convert_half( a.lo); 
+  return r;
+}
+void avx_test( uint16_t *destData, float16 argbF)
+{
+   ((half16U*)destData)[0] = convert_half(argbF);
+}