[CodeGen] Only consider innermost cast for !heapallocsite

Without opaque pointers, this code determined !heapallocsite based
on the innermost cast of the allocation call. With opaque pointers,
the casts no longer generate an instruction, so the outermost cast
is used. Add an explicit check for nested casts to prevent this.

Differential Revision: https://reviews.llvm.org/D145788

clang/lib/CodeGen/CGExprScalar.cpp

@@ -2098,7 +2098,8 @@ Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
 
     // Update heapallocsite metadata when there is an explicit pointer cast.
     if (auto *CI = dyn_cast<llvm::CallBase>(Src)) {
-      if (CI->getMetadata("heapallocsite") && isa<ExplicitCastExpr>(CE)) {
+      if (CI->getMetadata("heapallocsite") && isa<ExplicitCastExpr>(CE) &&
+          !isa<CastExpr>(E)) {
         QualType PointeeType = DestTy->getPointeeType();
         if (!PointeeType.isNull())
           CGF.getDebugInfo()->addHeapAllocSiteMetadata(CI, PointeeType,

clang/test/CodeGen/debug-info-codeview-heapallocsite.c

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -no-opaque-pointers -triple x86_64-windows-msvc -debug-info-kind=limited -gcodeview -fdeclspec -S -emit-llvm %s -o - | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-windows-msvc -debug-info-kind=limited -gcodeview -fdeclspec -S -emit-llvm %s -o - | FileCheck %s
 
 struct Foo;
 struct Bar;
@@ -14,10 +14,10 @@ void call_alloc(void) {
 }
 
 // CHECK-LABEL: define {{.*}}void @call_alloc
-// CHECK: call i8* {{.*}}@alloc_void{{.*}} !heapallocsite [[DBG1:!.*]]
-// CHECK: call %struct.Foo* {{.*}}@alloc_foo{{.*}} !heapallocsite [[DBG2:!.*]]
-// CHECK: call i8* {{.*}}@alloc_void{{.*}} !heapallocsite [[DBG2]]
-// CHECK: call i8* {{.*}}@alloc_void{{.*}} !heapallocsite [[DBG3:!.*]]
+// CHECK: call ptr {{.*}}@alloc_void{{.*}} !heapallocsite [[DBG1:!.*]]
+// CHECK: call ptr {{.*}}@alloc_foo{{.*}} !heapallocsite [[DBG2:!.*]]
+// CHECK: call ptr {{.*}}@alloc_void{{.*}} !heapallocsite [[DBG2]]
+// CHECK: call ptr {{.*}}@alloc_void{{.*}} !heapallocsite [[DBG3:!.*]]
 
 // CHECK: [[DBG2]] = !DICompositeType(tag: DW_TAG_structure_type,
 // CHECK-SAME:                                 name: "Foo"