Add basic reflection query for checking if entry point is "sample-rate"

- This really just checks two basic things:
  1. Was there any global variable declared with `in` and `sample`?
  2. Did any code encountered during lowering referenece `gl_SampleIndex`?

- This doesn't cover what HLSL could need, nor what we would need for cross-compilation. Consider it GLSL-specific for now.

- In order to generate the information with even a reasonable chance of being accurate (not giving a ton of false positives) I tried to integrate the checks into the lowering process (so they only see code that is referenced, one hopes).
  - For this to work with my testing setup, I needed to make sure that lowering is always performed, prior to emitting reflection info
  - This change broke several reflection tests, because they had been using code that wouldn't actually pass the downstream compiler. I checked in fixes for those.

1 files changed, 55 insertions, 0 deletions

diff --git a/tests/reflection/sample-rate-input.glsl.expected b/tests/reflection/sample-rate-input.glsl.expected
new file mode 100644
index 000000000..5800a3630
--- /dev/null
+++ b/tests/reflection/sample-rate-input.glsl.expected
@@ -0,0 +1,55 @@
+result code = 0
+standard error = {
+}
+standard output = {
+{
+    "parameters": [
+        {
+            "name": "t",
+            "binding": {"kind": "descriptorTableSlot", "index": 0},
+            "type": {
+                "kind": "resource",
+                "baseShape": "texture2D"
+            }
+        },
+        {
+            "name": "s",
+            "binding": {"kind": "descriptorTableSlot", "index": 1},
+            "type": {
+                "kind": "samplerState"
+            }
+        },
+        {
+            "name": "uv",
+            "binding": {"kind": "vertexInput", "index": 0},
+            "type": {
+                "kind": "vector",
+                "elementCount": 2,
+                "elementType": {
+                    "kind": "scalar",
+                    "scalarType": "float32"
+                }
+            }
+        },
+        {
+            "name": "c",
+            "binding": {"kind": "fragmentOutput", "index": 0},
+            "type": {
+                "kind": "vector",
+                "elementCount": 4,
+                "elementType": {
+                    "kind": "scalar",
+                    "scalarType": "float32"
+                }
+            }
+        }
+    ],
+    "entryPoints": [
+        {
+            "name": "main",
+            "stage:": "fragment",
+            "usesAnySampleRateInput": true
+        }
+    ]
+}
+}