[CodeGen] Point empty %invoke.cont block to successor

[vsk]

Summary

When partially initializing a global, exception-handling code in the frontend emits a placeholder %invoke.cont block with no terminator. This commit adds a suitable BranchInst to the block to prevent "malformed BasicBlock" errors.

A test case is included.

Note: I have been struggling to understand why throwing an error in a destructor causes exception-handling code to be generated when invoking the constructor [esp. when the constructor does not throw anything]. This patch is meant as a workaround until the 'real' issue can be addressed.

[vsk]

Ping

[rnk]

I think a better fix would be to insert a non-terminator placeholder that doesn't confuse EmitBlock.

cfe/trunk/lib/CodeGen/CGExprAgg.cpp

for (const auto *field : record->fields()) {
     // FIXME: if we have an array of structures, all explicitly
     // initialized, we can end up pushing a linear number of cleanups.
     bool pushedCleanup = false;
     if (QualType::DestructionKind dtorKind
           = field->getType().isDestructedType()) {
       assert(LV.isSimple());
       if (CGF.needsEHCleanup(dtorKind)) {
         if (!cleanupDominator)
-          cleanupDominator = CGF.Builder.CreateUnreachable(); // placeholder
+          cleanupDominator = CGF.Builder.CreateLoad(
+              CGF.Int8Ty,
+              llvm::Constant::getNullValue(CGF.Int8PtrTy)); // placeholder
 
         CGF.pushDestroy(EHCleanup, LV.getAddress(), field->getType(),
                         CGF.getDestroyer(dtorKind), false);
         cleanups.push_back(CGF.EHStack.stable_begin());
         pushedCleanup = true;
       }
     }
     

cfe/trunk/test/CodeGenCXX/partial-init.cpp

+// RUN: %clang_cc1 -triple %itanium_abi_triple -emit-llvm -std=c++11 -fcxx-exceptions -fexceptions -S -emit-llvm -o - %s | FileCheck %s
+
+namespace std {
+  struct string {
+    const char *p;
+    string(const char *s);
+    ~string();
+  };
+}
+
+struct Bar {
+  int a;
+};
+
+struct Foo {
+  std::string c;
+  Bar d[32];
+};
+
+static Foo table[] = {
+  { "blerg" },
+};
+
+// CHECK: define internal void @__cxx_global_var_init
+// CHECK: invoke void @_ZNSt6stringC1EPKc(
+// CHECK-NOT: unreachable
+// CHECK: br label