[spirv-writer] Don't emit abstract accessor source

When traverseing an accessor expression, stop as soon as we hit a
source object that has a constant value. This prevents us from trying
to emit expressions that have abstract types and no materialization
nodes.

Bug: chromium:1442551
Change-Id: I8296ae58e63624e647052cdf966dbff15630a4d8
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/132040
Auto-Submit: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

src/tint/writer/spirv/builder.cc

@@ -1034,6 +1034,11 @@ uint32_t Builder::GenerateAccessorExpression(const ast::AccessorExpression* expr
         } else {
             break;
         }
+
+        // Stop traversing if we've hit a constant source expression.
+        if (builder_.Sem().GetVal(source)->ConstantValue()) {
+            break;
+        }
     }
 
     AccessorInfo info;

test/tint/bug/chromium/1442551.wgsl

@@ -0,0 +1,5 @@
+fn f() {
+  const v = vec3(1, 2, 3);
+  let i = 1;
+  var b = v.rg[i];
+}

test/tint/bug/chromium/1442551.wgsl.expected.dxc.hlsl

@@ -0,0 +1,9 @@
+[numthreads(1, 1, 1)]
+void unused_entry_point() {
+  return;
+}
+
+void f() {
+  const int i = 1;
+  int b = int2(1, 2)[i];
+}

test/tint/bug/chromium/1442551.wgsl.expected.fxc.hlsl

@@ -0,0 +1,9 @@
+[numthreads(1, 1, 1)]
+void unused_entry_point() {
+  return;
+}
+
+void f() {
+  const int i = 1;
+  int b = int2(1, 2)[i];
+}

test/tint/bug/chromium/1442551.wgsl.expected.glsl

@@ -0,0 +1,11 @@
+#version 310 es
+
+layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
+void unused_entry_point() {
+  return;
+}
+void f() {
+  int i = 1;
+  int b = ivec2(1, 2)[i];
+}
+

test/tint/bug/chromium/1442551.wgsl.expected.msl

@@ -0,0 +1,8 @@
+#include <metal_stdlib>
+
+using namespace metal;
+void f() {
+  int const i = 1;
+  int b = int2(1, 2)[i];
+}
+

test/tint/bug/chromium/1442551.wgsl.expected.spvasm

@@ -0,0 +1,32 @@
+; SPIR-V
+; Version: 1.3
+; Generator: Google Tint Compiler; 0
+; Bound: 16
+; Schema: 0
+               OpCapability Shader
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint GLCompute %unused_entry_point "unused_entry_point"
+               OpExecutionMode %unused_entry_point LocalSize 1 1 1
+               OpName %unused_entry_point "unused_entry_point"
+               OpName %f "f"
+               OpName %b "b"
+       %void = OpTypeVoid
+          %1 = OpTypeFunction %void
+        %int = OpTypeInt 32 1
+      %int_1 = OpConstant %int 1
+      %v2int = OpTypeVector %int 2
+      %int_2 = OpConstant %int 2
+         %11 = OpConstantComposite %v2int %int_1 %int_2
+%_ptr_Function_int = OpTypePointer Function %int
+         %15 = OpConstantNull %int
+%unused_entry_point = OpFunction %void None %1
+          %4 = OpLabel
+               OpReturn
+               OpFunctionEnd
+          %f = OpFunction %void None %1
+          %6 = OpLabel
+          %b = OpVariable %_ptr_Function_int Function %15
+         %12 = OpVectorExtractDynamic %int %11 %int_1
+               OpStore %b %12
+               OpReturn
+               OpFunctionEnd

test/tint/bug/chromium/1442551.wgsl.expected.wgsl

@@ -0,0 +1,5 @@
+fn f() {
+  const v = vec3(1, 2, 3);
+  let i = 1;
+  var b = v.rg[i];
+}