Fix debug info generation for this (microsoft#5534)

My recent changes to correct AST inaccuracies around `this` objects
caused crashes in debug info generation for `this`. This resolves the
crashes by making the code behave correctly when `this` is a reference.

This has no change to debug info output. The added test case should
verify the same output we've always had, but is an important addition
since this was not tested in our pre-merge testing.

Fixes microsoft#5530

Author: llvm-beanz

tools/clang/lib/CodeGen/CGDebugInfo.cpp

@@ -1116,11 +1116,12 @@ llvm::DISubroutineType *CGDebugInfo::getOrCreateInstanceMethodType(
   const CXXRecordDecl *RD = ThisPtr->getPointeeCXXRecordDecl();
   if (isa<ClassTemplateSpecializationDecl>(RD)) {
     // Create pointer type directly in this case.
-    const PointerType *ThisPtrTy = cast<PointerType>(ThisPtr);
-    QualType PointeeTy = ThisPtrTy->getPointeeType();
+    // HLSL Change Begin - This is a reference.
+    QualType PointeeTy = ThisPtr->getPointeeType();
     unsigned AS = CGM.getContext().getTargetAddressSpace(PointeeTy);
     uint64_t Size = CGM.getTarget().getPointerWidth(AS);
-    uint64_t Align = CGM.getContext().getTypeAlign(ThisPtrTy);
+    uint64_t Align = CGM.getContext().getTypeAlign(ThisPtr.getTypePtr());
+    // HLSL Change End - This is a reference.
     llvm::DIType *PointeeType = getOrCreateType(PointeeTy, Unit);
     llvm::DIType *ThisPtrType =
         DBuilder.createPointerType(PointeeType, Size, Align);

tools/clang/test/HLSLFileCheck/hlsl/template/templateStructFunc.hlsl

@@ -1,13 +1,17 @@
-// RUN: %dxc -E main -T ps_6_0 -HV 2021 %s | FileCheck %s
+// RUN: %dxc -E main -T ps_6_0 -fcgl %s | FileCheck %s
+// RUN: %dxc -E main -T ps_6_0 -fcgl -Zi -Qembed_debug %s | FileCheck -check-prefixes=CHECK,DI %s
+
+// The goal of this test is to verify the instantiations of `foo` are correctly
+// generated _and_ to verify that the correct debug information is generated for
+// the instantiations.
 
-// CHECK:define void @main
 
 template<typename T>
 struct Test {
 
 T t;
 T foo(T t1) {
-  return sin(t) * cos(t1);
+  return t * t1;
 }
 
 };
@@ -19,3 +23,53 @@ float2 main(float4 a:A) : SV_Target {
   t1.t = a.xy;
   return t0.foo(a.y) + t1.foo(a.zw);
 }
+
+
+// CHECK: define internal float @"\01?foo@?$Test@{{[A-Z0-9@]+}}"
+// CHECK-SAME: (%"struct.Test<float>"* [[this:%.*]], float [[t1:%.*]])
+
+// CHECK: [[t1LocalAddr:%.*]] = alloca float,
+// CHECK-NEXT: store float [[t1]], float* [[t1LocalAddr]]
+
+// DI-NEXT: call void @llvm.dbg.declare(metadata float* [[t1LocalAddr]], metadata [[t1FVar:![0-9]+]]
+// DI-NEXT: call void @llvm.dbg.declare(metadata %"struct.Test<float>"* [[this]], metadata [[thisFVar:![0-9]+]]
+
+// CHECK-NEXT: [[this_tAddr:%.*]] = getelementptr inbounds %"struct.Test<float>", %"struct.Test<float>"* [[this]], i32 0, i32 0,
+// CHECK-NEXT: [[this_t:%.*]] = load float, float* [[this_tAddr]],
+// CHECK-NEXT: [[t1Local:%.*]] = load float, float* [[t1LocalAddr]],
+// CHECK-NEXT: [[Res:%.*]] = fmul float [[this_t]], [[t1Local]]
+// CHECK-NEXT: ret float [[Res]]
+
+
+// CHECK: define internal <2 x float> @"\01?foo@?$Test@V?$vector{{[A-Za-z0-9@?$]+}}"
+// CHECK-SAME: (%"struct.Test<vector<float, 2> >"* [[this:%.*]], <2 x float> [[t1:%.*]])
+
+// CHECK: [[t1LocalAddr:%.*]] = alloca <2 x float>
+// CHECK-NEXT: store <2 x float> [[t1]], <2 x float>* [[t1LocalAddr]]
+
+// DI-NEXT: call void @llvm.dbg.declare(metadata <2 x float>* [[t1LocalAddr]], metadata [[t1VVar:![0-9]+]]
+// DI-NEXT: call void @llvm.dbg.declare(metadata %"struct.Test<vector<float, 2> >"* [[this]], metadata [[thisVVar:![0-9]+]]
+
+// CHECK-NEXT: [[this_tAddr:%.*]] = getelementptr inbounds %"struct.Test<vector<float, 2> >", %"struct.Test<vector<float, 2> >"* [[this]], i32 0, i32 0
+// CHECK-NEXT: [[this_t:%.*]] = load <2 x float>, <2 x float>* [[this_tAddr]]
+// CHECK-NEXT: [[t1Local:%.*]] = load <2 x float>, <2 x float>* [[t1LocalAddr]]
+// CHECK-NEXT: [[Res:%.*]] = fmul <2 x float> [[this_t]], [[t1Local]]
+// CHECK-NEXT  ret <2 x float> [[Res]]
+
+
+// DI: [[DIFile:![0-9]+]] = !DIFile
+// DI-DAG: [[DIFloat:![0-9]+]] = !DIBasicType(name: "float", size: 32, align: 32, encoding: DW_ATE_float)
+
+// DI-DAG: [[FSub:![0-9]+]] = !DISubprogram(name: "foo", linkageName: "\01?foo@?$Test@{{[A-Z@0-9]+}}", scope: [[FloatScope:![0-9]+]], file: [[DIFile]], line: {{[0-9]+}}, type: {{![0-9]+}}, isLocal: false, isDefinition: true, scopeLine: {{[0-9]+}}, flags: DIFlagPrototyped, isOptimized: false, function: float (%"struct.Test<float>"*, float)* @"\01?foo@?$Test@{{[A-Z@0-9]+}}",
+// DI-DAG: [[DITestF:![0-9]+]] = !DICompositeType(tag: DW_TAG_structure_type, name: "Test<float>"
+
+// DI-DAG: [[VSub:![0-9]+]] = !DISubprogram(name: "foo", linkageName: "\01?foo@?$Test@V?$vector{{[A-Za-z0-9@?$]+}}", scope: [[VecScope:![0-9]+]], file: [[DIFile]], line: {{[0-9]+}}, type: {{![0-9]+}}, isLocal: false, isDefinition: true, scopeLine: {{[0-9]+}}, flags: DIFlagPrototyped, isOptimized: false, function: <2 x float> (%"struct.Test<vector<float, 2> >"*, <2 x float>)* @"\01?foo@?$Test@V?$vector{{[A-Za-z0-9@?$]+}}",
+// DI-DAG: [[DITestV:![0-9]+]] = !DICompositeType(tag: DW_TAG_structure_type, name: "Test<vector<float, 2> >", file: [[DIFile]], line: {{[0-9]+}}, size: 64, align: 32
+
+// DI-DAG: [[t1FVar]] = !DILocalVariable(tag: DW_TAG_arg_variable, name: "t1", arg: 2, scope: [[FSub]], file: [[DIFile]], line: {{[0-9]+}}, type: [[DIFloat]])
+// DI-DAG: [[thisFVar]] = !DILocalVariable(tag: DW_TAG_arg_variable, name: "this", arg: 1, scope: [[FSub]], type: [[thisFPtr:![0-9]+]])
+// DI-DAG: [[thisFPtr]] = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: [[DITestF]], size: 32, align: 32)
+
+// DI-DAG: [[t1VVar]] = !DILocalVariable(tag: DW_TAG_arg_variable, name: "t1", arg: 2, scope: [[VSub]], file: [[DIFile]]
+// DI-DAG: [[thisVVar]] = !DILocalVariable(tag: DW_TAG_arg_variable, name: "this", arg: 1, scope: [[VSub]], type: [[thisVPtr:![0-9]+]])
+// DI-DAG: [[thisVPtr]] = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: [[DITestV]], size: 32, align: 32)