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, 2 insertions, 2 deletions

diff --git a/tests/reflection/multi-file-extra.hlsl b/tests/reflection/multi-file-extra.hlsl
index 569ec2ce9..a5da70635 100644
--- a/tests/reflection/multi-file-extra.hlsl
+++ b/tests/reflection/multi-file-extra.hlsl
@@ -18,7 +18,7 @@ float4 use(float  val) { return val; };
 float4 use(float2 val) { return float4(val,0.0,0.0); };
 float4 use(float3 val) { return float4(val,0.0); };
 float4 use(float4 val) { return val; };
-float4 use(Texture2D t, SamplerState s) { return t.Sample(s, 0.0); }
+float4 use(Texture2D t, SamplerState s) { return t.SampleLevel(s, 0.0, 0.0); }
 
 // Start with some parameters that will appear in both shaders
 Texture2D sharedT;
@@ -51,7 +51,7 @@ Texture2D sharedTV;
 Texture2D sharedTF;
 
 
-float4 main() : SV_Target
+float4 mainVS() : SV_Position
 {
 	// Go ahead and use everything here, just to make sure things got placed correctly
 	return use(sharedT, sharedS)