[DEBUG INFO] Emit debug info for type used in explicit cast only.

[ABataev]

Summary

Currently debug info for types used in explicit cast only is not emitted. It happened after a patch for better alignment handling. This patch fixes this bug.

[ABataev]

Update after review

[rjmccall]

That looks great, thank you.

lib/CodeGen/CGExpr.cpp

Address CodeGenFunction::EmitPointerWithAlignment(const Expr *E,
   E = E->IgnoreParens();
 
   // Casts:
   if (const CastExpr *CE = dyn_cast<CastExpr>(E)) {
     // Bind VLAs in the cast type.
     if (E->getType()->isVariablyModifiedType())
       EmitVariablyModifiedType(E->getType());
 
+    if (isa<ExplicitCastExpr>(CE))
+      if (CGDebugInfo *DI = getDebugInfo())
+        DI->EmitExplicitCastType(E->getType());
+
     switch (CE->getCastKind()) {
     // Non-converting casts (but not C's implicit conversion from void*).
     case CK_BitCast:
     case CK_NoOp:
       if (auto PtrTy = CE->getSubExpr()->getType()->getAs<PointerType>()) {
         if (PtrTy->getPointeeType()->isVoidType())
           break;
 

test/CodeGenCXX/debug-info-explicit-cast.cpp

+// RUN: %clangxx -c -target x86_64-unknown-unknown -g %s -emit-llvm -S -o - | FileCheck %s
+struct Foo {
+  int a;
+  Foo() : a(1){};
+};
+
+struct Bar {
+  int b;
+  Bar() : b(2){};
+};
+
+int main() {
+  Bar *pb = new Bar;
+
+  return reinterpret_cast<Foo *>(pb)->a;
+}
+
+// CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "Foo",