spirv-reader: switch to HLSL-style pipeline IO

- When storing to sample_mask output, write to the 0th element
- Only make a return struct if it has members
- Adjust type signedness coercion when loading special builtins.
- Adapt tests

- Update expectations for end-to-end tests

- Handle sample_mask with stride
  Input variables normally don't have layout. But they can have it
  up through SPIR-V 1.4.
  Handle this case in the SPIR-V reader, by seeing through the
  intermediate alias type created for the strided array type.

Bug: tint:508
Change-Id: I0f19dc1305d3f250dbbc0698a602288c34245274
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/54743
Auto-Submit: David Neto <dneto@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: James Price <jrprice@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>

test/ptr_ref/copy/ptr_copy.spvasm.expected.hlsl

@@ -1,5 +1,10 @@
-[numthreads(1, 1, 1)]
-void main() {
+void main_1() {
   uint x_10 = 0u;
   return;
 }
+
+[numthreads(1, 1, 1)]
+void main() {
+  main_1();
+  return;
+}

test/ptr_ref/copy/ptr_copy.spvasm.expected.msl

@@ -1,10 +1,15 @@
 #include <metal_stdlib>
 
 using namespace metal;
-kernel void tint_symbol() {
+void main_1() {
   uint x_10 = 0u;
   thread uint* const x_1 = &(x_10);
   thread uint* const x_2 = x_1;
   return;
 }
 
+kernel void tint_symbol() {
+  main_1();
+  return;
+}
+

test/ptr_ref/copy/ptr_copy.spvasm.expected.spvasm

@@ -1,21 +1,27 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 9
+; Bound: 12
 ; Schema: 0
                OpCapability Shader
                OpMemoryModel Logical GLSL450
                OpEntryPoint GLCompute %main "main"
                OpExecutionMode %main LocalSize 1 1 1
-               OpName %main "main"
+               OpName %main_1 "main_1"
                OpName %x_10 "x_10"
+               OpName %main "main"
        %void = OpTypeVoid
           %1 = OpTypeFunction %void
        %uint = OpTypeInt 32 0
 %_ptr_Function_uint = OpTypePointer Function %uint
           %8 = OpConstantNull %uint
-       %main = OpFunction %void None %1
+     %main_1 = OpFunction %void None %1
           %4 = OpLabel
        %x_10 = OpVariable %_ptr_Function_uint Function %8
                OpReturn
                OpFunctionEnd
+       %main = OpFunction %void None %1
+         %10 = OpLabel
+         %11 = OpFunctionCall %void %main_1
+               OpReturn
+               OpFunctionEnd

test/ptr_ref/copy/ptr_copy.spvasm.expected.wgsl

@@ -1,7 +1,11 @@
-[[stage(compute)]]
-fn main() {
+fn main_1() {
   var x_10 : u32;
   let x_1 : ptr<function, u32> = &(x_10);
   let x_2 : ptr<function, u32> = x_1;
   return;
 }
+
+[[stage(compute)]]
+fn main() {
+  main_1();
+}