Add sample-rate-input detection for HLSL. (#312)

* Add sample-rate-input detection for HLSL.

In the HLSL case, it is possible to do this detection entirely based on declared signatures (it doesn't have a dependency on code generation like the GLSL case does). I've added test cases for the two main ways that a shader can become sample rate:

1. Qualify a fragment input with `sample`
2. Accept an input with the `SV_SampleIndex` semantic

In each case I nested the input inside a `struct` to try to match common HLSL idiom, and to make sure that we handle the nested case.

This code is *not* robust against shaders that declare such an input and then never use it, but that is to be expected given the goals for Slang.

* Fixup: add missing test output files

1 files changed, 52 insertions, 0 deletions

diff --git a/tests/reflection/sample-index-input.hlsl.expected b/tests/reflection/sample-index-input.hlsl.expected
new file mode 100644
index 000000000..5bf5f297e
--- /dev/null
+++ b/tests/reflection/sample-index-input.hlsl.expected
@@ -0,0 +1,52 @@
+result code = 0
+standard error = {
+}
+standard output = {
+{
+    "parameters": [
+
+    ],
+    "entryPoints": [
+        {
+            "name": "main",
+            "stage:": "fragment",
+            "parameters": [
+                {
+                    "name": "input",
+                    "stage": "fragment",
+                    "binding": {"kind": "varyingInput", "index": 0},
+                    "type": {
+                        "kind": "struct",
+                        "name": "PSInput",
+                        "fields": [
+                            {
+                                "name": "color",
+                                "type": {
+                                    "kind": "vector",
+                                    "elementCount": 4,
+                                    "elementType": {
+                                        "kind": "scalar",
+                                        "scalarType": "float32"
+                                    }
+                                },
+                                "stage": "fragment",
+                                "binding": {"kind": "varyingInput", "index": 0},
+                                "semanticName": "COLOR"
+                            },
+                            {
+                                "name": "sampleIndex",
+                                "type": {
+                                    "kind": "scalar",
+                                    "scalarType": "uint32"
+                                },
+                                "semanticName": "SV_SAMPLEINDEX"
+                            }
+                        ]
+                    }
+                }
+            ],
+            "usesAnySampleRateInput": true
+        }
+    ]
+}
+}