writer/hlsl: Simplify emission logic, clean up output

And fix issues where global variables would not be emitted unless they were transitively referenced by an entry point.

This change requires crbug.com/tint/697 to be fixed before landing.

Change-Id: I712bd9d369e08c9a3cdfb0f114c3609584f91f28
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/54241
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>

test/samples/compute_boids.wgsl.expected.hlsl

@@ -6,26 +6,6 @@ struct tint_symbol_1 {
 struct tint_symbol_2 {
   float4 value : SV_Position;
 };
-struct tint_symbol_3 {
-  float4 value : SV_Target0;
-};
-struct SimParams {
-  float deltaT;
-  float rule1Distance;
-  float rule2Distance;
-  float rule3Distance;
-  float rule1Scale;
-  float rule2Scale;
-  float rule3Scale;
-};
-struct tint_symbol_5 {
-  uint3 gl_GlobalInvocationID : SV_DispatchThreadID;
-};
-
-ConstantBuffer<SimParams> params : register(b0, space0);
-
-RWByteAddressBuffer particlesA : register(u1, space0);
-RWByteAddressBuffer particlesB : register(u2, space0);
 
 tint_symbol_2 vert_main(tint_symbol_1 tint_symbol) {
   const float2 a_particlePos = tint_symbol.a_particlePos;
@@ -37,11 +17,33 @@ tint_symbol_2 vert_main(tint_symbol_1 tint_symbol) {
   return tint_symbol_8;
 }
 
+struct tint_symbol_3 {
+  float4 value : SV_Target0;
+};
+
 tint_symbol_3 frag_main() {
   const tint_symbol_3 tint_symbol_9 = {float4(1.0f, 1.0f, 1.0f, 1.0f)};
   return tint_symbol_9;
 }
 
+struct SimParams {
+  float deltaT;
+  float rule1Distance;
+  float rule2Distance;
+  float rule3Distance;
+  float rule1Scale;
+  float rule2Scale;
+  float rule3Scale;
+};
+
+ConstantBuffer<SimParams> params : register(b0, space0);
+RWByteAddressBuffer particlesA : register(u1, space0);
+RWByteAddressBuffer particlesB : register(u2, space0);
+
+struct tint_symbol_5 {
+  uint3 gl_GlobalInvocationID : SV_DispatchThreadID;
+};
+
 [numthreads(1, 1, 1)]
 void comp_main(tint_symbol_5 tint_symbol_4) {
   const uint3 gl_GlobalInvocationID = tint_symbol_4.gl_GlobalInvocationID;
@@ -113,4 +115,3 @@ void comp_main(tint_symbol_5 tint_symbol_4) {
   particlesB.Store2(((16u * index) + 8u), asuint(vVel));
   return;
 }
-

test/samples/cube.wgsl.expected.hlsl

@@ -1,6 +1,9 @@
 struct Uniforms {
   float4x4 modelViewProjectionMatrix;
 };
+
+ConstantBuffer<Uniforms> uniforms : register(b0, space0);
+
 struct VertexInput {
   float4 cur_position;
   float4 color;
@@ -17,14 +20,6 @@ struct tint_symbol_2 {
   float4 vtxFragColor : TEXCOORD0;
   float4 Position : SV_Position;
 };
-struct tint_symbol_4 {
-  float4 fragColor : TEXCOORD0;
-};
-struct tint_symbol_5 {
-  float4 value : SV_Target0;
-};
-
-ConstantBuffer<Uniforms> uniforms : register(b0, space0);
 
 tint_symbol_2 vtx_main(tint_symbol_1 tint_symbol) {
   const VertexInput input = {tint_symbol.cur_position, tint_symbol.color};
@@ -35,9 +30,15 @@ tint_symbol_2 vtx_main(tint_symbol_1 tint_symbol) {
   return tint_symbol_6;
 }
 
+struct tint_symbol_4 {
+  float4 fragColor : TEXCOORD0;
+};
+struct tint_symbol_5 {
+  float4 value : SV_Target0;
+};
+
 tint_symbol_5 frag_main(tint_symbol_4 tint_symbol_3) {
   const float4 fragColor = tint_symbol_3.fragColor;
   const tint_symbol_5 tint_symbol_7 = {fragColor};
   return tint_symbol_7;
 }
-

test/samples/function.wgsl.expected.hlsl

@@ -6,4 +6,3 @@ float main() {
 void ep() {
   return;
 }
-

test/samples/simple.wgsl.expected.hlsl

@@ -1,14 +1,13 @@
+void bar() {
+}
+
 struct tint_symbol {
   float4 value : SV_Target0;
 };
 
-void bar() {
-}
-
 tint_symbol main() {
   float2 a = float2(0.0f, 0.0f);
   bar();
   const tint_symbol tint_symbol_1 = {float4(0.400000006f, 0.400000006f, 0.800000012f, 1.0f)};
   return tint_symbol_1;
 }
-

test/samples/simple_vertex.spvasm.expected.hlsl

@@ -1,10 +1,10 @@
-struct main_out {
-  float4 gl_Position : SV_Position;
-};
+SKIP: FAILED
 
-main_out main() {
-  main_out tint_out = (main_out)0;
-  tint_out.gl_Position = float4(0.0f, 0.0f, 0.0f, 0.0f);
-  return tint_out;
-}
+../src/writer/hlsl/generator_impl.cc:1726 internal compiler error: unhandled storage class out
+********************************************************************
+*  The tint shader compiler has encountered an unexpected error.   *
+*                                                                  *
+*  Please help us fix this issue by submitting a bug report at     *
+*  crbug.com/tint with the source program that triggered the bug.  *
+********************************************************************
 

test/samples/triangle.wgsl.expected.hlsl

@@ -1,22 +1,23 @@
+static const float2 pos[3] = {float2(0.0f, 0.5f), float2(-0.5f, -0.5f), float2(0.5f, -0.5f)};
+
 struct tint_symbol_1 {
   uint VertexIndex : SV_VertexID;
 };
 struct tint_symbol_2 {
   float4 value : SV_Position;
 };
-struct tint_symbol_3 {
-  float4 value : SV_Target0;
-};
 
-static const float2 pos[3] = {float2(0.0f, 0.5f), float2(-0.5f, -0.5f), float2(0.5f, -0.5f)};
 tint_symbol_2 vtx_main(tint_symbol_1 tint_symbol) {
   const uint VertexIndex = tint_symbol.VertexIndex;
   const tint_symbol_2 tint_symbol_4 = {float4(pos[VertexIndex], 0.0f, 1.0f)};
   return tint_symbol_4;
 }
 
+struct tint_symbol_3 {
+  float4 value : SV_Target0;
+};
+
 tint_symbol_3 frag_main() {
   const tint_symbol_3 tint_symbol_5 = {float4(1.0f, 0.0f, 0.0f, 1.0f)};
   return tint_symbol_5;
 }
-