transform/shader_io: Generate a wrapper function

This is a major reworking of this transform. The old transform code
was getting unwieldy, with part of the complication coming from the
handling of multiple return statements. By generating a wrapper
function instead, we can avoid a lot of this complexity.

The original entry point function is stripped of all shader IO
attributes (as well as `stage` and `workgroup_size`), but the body is
left unmodified. A new entry point wrapper function is introduced
which calls the original function, packing/unpacking the shader inputs
as necessary, and propagates the result to the corresponding shader
outputs.

The new code has been refactored to use a state object with the
different parts of the transform split into separate functions, which
makes it much more manageable.

Fixed: tint:1076
Bug: tint:920
Change-Id: I3490a0ea7a3509a4e198ce730e476516649d8d96
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/60521
Auto-Submit: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: James Price <jrprice@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>

test/vk-gl-cts/graphicsfuzz/disc-and-add-in-func-in-loop/0-opt.spvasm.expected.hlsl

@@ -69,9 +69,15 @@ struct tint_symbol {
   float4 x_GLF_color_1 : SV_Target0;
 };
 
-tint_symbol main() {
+main_out main_inner() {
   main_1();
-  const main_out tint_symbol_1 = {x_GLF_color};
-  const tint_symbol tint_symbol_3 = {tint_symbol_1.x_GLF_color_1};
-  return tint_symbol_3;
+  const main_out tint_symbol_2 = {x_GLF_color};
+  return tint_symbol_2;
+}
+
+tint_symbol main() {
+  const main_out inner_result = main_inner();
+  tint_symbol wrapper_result = (tint_symbol)0;
+  wrapper_result.x_GLF_color_1 = inner_result.x_GLF_color_1;
+  return wrapper_result;
 }

test/vk-gl-cts/graphicsfuzz/disc-and-add-in-func-in-loop/0-opt.spvasm.expected.msl

@@ -15,7 +15,7 @@ void x_51() {
   discard_fragment();
 }
 
-void main_1(constant buf0& x_5, thread float4* const tint_symbol_4) {
+void main_1(constant buf0& x_5, thread float4* const tint_symbol_3) {
   while (true) {
     bool x_31 = false;
     bool x_30_phi = false;
@@ -46,7 +46,7 @@ void main_1(constant buf0& x_5, thread float4* const tint_symbol_4) {
           break;
         }
         float4 const x_55 = x_55_phi;
-        *(tint_symbol_4) = x_55;
+        *(tint_symbol_3) = x_55;
         x_31_phi = true;
         break;
       }
@@ -71,11 +71,17 @@ void main_1(constant buf0& x_5, thread float4* const tint_symbol_4) {
   return;
 }
 
-fragment tint_symbol_1 tint_symbol(constant buf0& x_5 [[buffer(0)]]) {
-  thread float4 tint_symbol_5 = 0.0f;
-  main_1(x_5, &(tint_symbol_5));
-  main_out const tint_symbol_2 = {.x_GLF_color_1=tint_symbol_5};
-  tint_symbol_1 const tint_symbol_3 = {.x_GLF_color_1=tint_symbol_2.x_GLF_color_1};
-  return tint_symbol_3;
+main_out tint_symbol_inner(constant buf0& x_5, thread float4* const tint_symbol_4) {
+  main_1(x_5, tint_symbol_4);
+  main_out const tint_symbol_2 = {.x_GLF_color_1=*(tint_symbol_4)};
+  return tint_symbol_2;
+}
+
+fragment tint_symbol_1 tint_symbol(constant buf0& x_5 [[buffer(0)]]) {
+  thread float4 tint_symbol_5 = 0.0f;
+  main_out const inner_result = tint_symbol_inner(x_5, &(tint_symbol_5));
+  tint_symbol_1 wrapper_result = {};
+  wrapper_result.x_GLF_color_1 = inner_result.x_GLF_color_1;
+  return wrapper_result;
 }
 

test/vk-gl-cts/graphicsfuzz/disc-and-add-in-func-in-loop/0-opt.wgsl.expected.hlsl

@@ -69,9 +69,15 @@ struct tint_symbol {
   float4 x_GLF_color_1 : SV_Target0;
 };
 
-tint_symbol main() {
+main_out main_inner() {
   main_1();
-  const main_out tint_symbol_1 = {x_GLF_color};
-  const tint_symbol tint_symbol_3 = {tint_symbol_1.x_GLF_color_1};
-  return tint_symbol_3;
+  const main_out tint_symbol_2 = {x_GLF_color};
+  return tint_symbol_2;
+}
+
+tint_symbol main() {
+  const main_out inner_result = main_inner();
+  tint_symbol wrapper_result = (tint_symbol)0;
+  wrapper_result.x_GLF_color_1 = inner_result.x_GLF_color_1;
+  return wrapper_result;
 }

test/vk-gl-cts/graphicsfuzz/disc-and-add-in-func-in-loop/0-opt.wgsl.expected.msl

@@ -15,7 +15,7 @@ void x_51() {
   discard_fragment();
 }
 
-void main_1(constant buf0& x_5, thread float4* const tint_symbol_4) {
+void main_1(constant buf0& x_5, thread float4* const tint_symbol_3) {
   while (true) {
     bool x_31 = false;
     bool x_30_phi = false;
@@ -46,7 +46,7 @@ void main_1(constant buf0& x_5, thread float4* const tint_symbol_4) {
           break;
         }
         float4 const x_55 = x_55_phi;
-        *(tint_symbol_4) = x_55;
+        *(tint_symbol_3) = x_55;
         x_31_phi = true;
         break;
       }
@@ -71,11 +71,17 @@ void main_1(constant buf0& x_5, thread float4* const tint_symbol_4) {
   return;
 }
 
-fragment tint_symbol_1 tint_symbol(constant buf0& x_5 [[buffer(0)]]) {
-  thread float4 tint_symbol_5 = 0.0f;
-  main_1(x_5, &(tint_symbol_5));
-  main_out const tint_symbol_2 = {.x_GLF_color_1=tint_symbol_5};
-  tint_symbol_1 const tint_symbol_3 = {.x_GLF_color_1=tint_symbol_2.x_GLF_color_1};
-  return tint_symbol_3;
+main_out tint_symbol_inner(constant buf0& x_5, thread float4* const tint_symbol_4) {
+  main_1(x_5, tint_symbol_4);
+  main_out const tint_symbol_2 = {.x_GLF_color_1=*(tint_symbol_4)};
+  return tint_symbol_2;
+}
+
+fragment tint_symbol_1 tint_symbol(constant buf0& x_5 [[buffer(0)]]) {
+  thread float4 tint_symbol_5 = 0.0f;
+  main_out const inner_result = tint_symbol_inner(x_5, &(tint_symbol_5));
+  tint_symbol_1 wrapper_result = {};
+  wrapper_result.x_GLF_color_1 = inner_result.x_GLF_color_1;
+  return wrapper_result;
 }