[clang] [HLSL] Add __is_scalarized_layout_compatible (PR #102227)

[Damyan Pepper via cfe-commits]

================
@@ -0,0 +1,132 @@
+// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.6-library -finclude-default-header -verify %s
+// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.6-library -finclude-default-header -fnative-half-type -verify %s
+// expected-no-diagnostics
+
+// Case 1: How many ways can I come up with to represent three float values?
+struct ThreeFloats1 {
+  float X, Y, Z;
+};
+
+struct ThreeFloats2 {
+  float X[3];
+};
+
+struct ThreeFloats3 {
+  float3 V;
+};
+
+struct ThreeFloats4 {
+  float2 V;
+  float F;
+};
+
+_Static_assert(__is_scalarized_layout_compatible(float3, float[3]), "");
+_Static_assert(__is_scalarized_layout_compatible(float3, ThreeFloats1), "");
+_Static_assert(__is_scalarized_layout_compatible(float3, ThreeFloats2), "");
+_Static_assert(__is_scalarized_layout_compatible(float3, ThreeFloats3), "");
+_Static_assert(__is_scalarized_layout_compatible(float3, ThreeFloats4), "");
+
+// Case 2: structs and base classes and arrays, oh my!
+struct Dog {
+  int Leg[4];
+  bool Tail;
+  float Fur;
+};
+
+struct Shiba {
+  int4 StubbyLegs;
+  bool CurlyTail;
+  struct Coating {
+    float Fur;
+  } F;
+};
+
+struct FourLegged {
+  int FR, FL, BR, BL;
+};
+
+struct Doggo : FourLegged {
+  bool WaggyBit;
+  float Fuzz;
+};
+
+_Static_assert(__is_scalarized_layout_compatible(Dog, Shiba), "");
+_Static_assert(__is_scalarized_layout_compatible(Dog, Doggo), "");
+
+// Case 3: Arrays of structs inside structs
+
+struct Cat {
+  struct Leg {
+    int L;
+  } Legs[4];
+  struct Other {
+    bool Tail;
+    float Furs;
+  } Bits;
+};
+
+_Static_assert(__is_scalarized_layout_compatible(Dog, Cat), "");
+
+// case 4: Arrays of structs inside arrays of structs.
+struct Pets {
+  Dog Puppers[6];
+  Cat Kitties[4];
+};
+
+struct Animals {
+  Dog Puppers[2];
+  Cat Kitties[8];
+};
+
+_Static_assert(__is_scalarized_layout_compatible(Pets, Animals), "");
+
+// Case 5: Turtles all the way down...
+
+typedef int Turtle;
+
+enum Ninja : Turtle {
+  Leonardo,
+  Donatello,
+  Michelangelo,
+  Raphael,
+};
+
+enum NotNinja : Turtle {
+  Fred,
+  Mikey,
+};
+
+enum Mammals : uint {
+  Dog,
+  Cat,
+};
+
+_Static_assert(__is_scalarized_layout_compatible(Ninja, NotNinja), "");
+_Static_assert(!__is_scalarized_layout_compatible(Ninja, Mammals), "");
+
+// Case 6: Some basic types.
+_Static_assert(__is_scalarized_layout_compatible(int, int32_t), "");
+_Static_assert(__is_scalarized_layout_compatible(uint, uint32_t), "");
+_Static_assert(!__is_scalarized_layout_compatible(int, uint), "");
+_Static_assert(!__is_scalarized_layout_compatible(int, float), "");
+
+// Even though half and float may be the same size we don't want them to be
+// layout compatible since they are different types.
+_Static_assert(!__is_scalarized_layout_compatible(half, float), "");
+
+// Case 6: Empty classes... because they're fun.
+
+struct NotEmpty { int X; };
+struct Empty {};
+struct AlsoEmpty {};
+
+struct DerivedEmpty : Empty {};
+
+struct DerivedNotEmpty : Empty { int X; };
+struct DerivedEmptyNotEmptyBase : NotEmpty {};
+
+_Static_assert(__is_scalarized_layout_compatible(Empty, AlsoEmpty), "");
+_Static_assert(__is_scalarized_layout_compatible(Empty, DerivedEmpty), "");
+
+_Static_assert(__is_scalarized_layout_compatible(NotEmpty, DerivedNotEmpty), "");
+_Static_assert(__is_scalarized_layout_compatible(NotEmpty, DerivedEmptyNotEmptyBase), "");
----------------
damyanp wrote:

test case for unions?

https://github.com/llvm/llvm-project/pull/102227