Test that only constant expressions are hoisted to initializers.

tests/in/const-exprs.wgsl

@@ -6,6 +6,7 @@ fn main() {
    swizzle_of_compose();
    index_of_compose();
    compose_three_deep();
+   non_constant_initializers();
 }
 
 // Swizzle the value of nested Compose expressions.
@@ -26,3 +27,22 @@ fn index_of_compose() {
 fn compose_three_deep() {
    out2 += vec4(vec3(vec2(6, 7), 8), 9)[0]; // should assign 6
 }
+
+// While WGSL allows local variables to be declared anywhere in the function,
+// Naga treats them all as appearing at the top of the function. To ensure that
+// WGSL initializer expressions are evaluated at the right time, in the general
+// case they need to be turned into Naga `Store` statements executed at the
+// point of the WGSL declaration.
+//
+// When a variable's initializer is a constant expression, however, it can be
+// evaluated at any time. The WGSL front end thus renders locals with
+// initializers that are constants as Naga locals with initializers. This test
+// checks that Naga local variable initializers are only used when safe.
+fn non_constant_initializers() {
+   var w = 10 + 20;
+   var x = w;
+   var y = x;
+   var z = 30 + 40;
+
+   out += vec4(w, x, y, z);
+}

tests/out/glsl/const-exprs.main.Compute.glsl

@@ -18,6 +18,24 @@ void index_of_compose() {
     return;
 }
 
+void non_constant_initializers() {
+    int w = 30;
+    int x = 0;
+    int y = 0;
+    int z = 70;
+    int _e2 = w;
+    x = _e2;
+    int _e4 = x;
+    y = _e4;
+    int _e9 = w;
+    int _e10 = x;
+    int _e11 = y;
+    int _e12 = z;
+    ivec4 _e14 = _group_0_binding_0_cs;
+    _group_0_binding_0_cs = (_e14 + ivec4(_e9, _e10, _e11, _e12));
+    return;
+}
+
 void swizzle_of_compose() {
     ivec2 a_1 = ivec2(1, 2);
     ivec2 b_1 = ivec2(3, 4);
@@ -35,6 +53,7 @@ void main() {
     swizzle_of_compose();
     index_of_compose();
     compose_three_deep();
+    non_constant_initializers();
     return;
 }
 

tests/out/hlsl/const-exprs.hlsl

@@ -10,6 +10,26 @@ void index_of_compose()
     return;
 }
 
+void non_constant_initializers()
+{
+    int w = 30;
+    int x = (int)0;
+    int y = (int)0;
+    int z = 70;
+
+    int _expr2 = w;
+    x = _expr2;
+    int _expr4 = x;
+    y = _expr4;
+    int _expr9 = w;
+    int _expr10 = x;
+    int _expr11 = y;
+    int _expr12 = z;
+    int4 _expr14 = asint(out_.Load4(0));
+    out_.Store4(0, asuint((_expr14 + int4(_expr9, _expr10, _expr11, _expr12))));
+    return;
+}
+
 void swizzle_of_compose()
 {
     int2 a_1 = int2(1, 2);
@@ -31,5 +51,6 @@ void main()
     swizzle_of_compose();
     index_of_compose();
     compose_three_deep();
+    non_constant_initializers();
     return;
 }

tests/out/msl/const-exprs.msl

@@ -15,6 +15,26 @@ void index_of_compose(
     return;
 }
 
+void non_constant_initializers(
+    device metal::int4& out
+) {
+    int w = 30;
+    int x = {};
+    int y = {};
+    int z = 70;
+    int _e2 = w;
+    x = _e2;
+    int _e4 = x;
+    y = _e4;
+    int _e9 = w;
+    int _e10 = x;
+    int _e11 = y;
+    int _e12 = z;
+    metal::int4 _e14 = out;
+    out = _e14 + metal::int4(_e9, _e10, _e11, _e12);
+    return;
+}
+
 void swizzle_of_compose(
     device metal::int4& out
 ) {
@@ -39,5 +59,6 @@ kernel void main_(
     swizzle_of_compose(out);
     index_of_compose(out2_);
     compose_three_deep(out2_);
+    non_constant_initializers(out);
     return;
 }

tests/out/spv/const-exprs.spvasm

@@ -1,13 +1,13 @@
 ; SPIR-V
 ; Version: 1.1
 ; Generator: rspirv
-; Bound: 55
+; Bound: 78
 OpCapability Shader
 OpExtension "SPV_KHR_storage_buffer_storage_class"
 %1 = OpExtInstImport "GLSL.std.450"
 OpMemoryModel Logical GLSL450
-OpEntryPoint GLCompute %48 "main"
-OpExecutionMode %48 LocalSize 1 1 1
+OpEntryPoint GLCompute %70 "main"
+OpExecutionMode %70 LocalSize 1 1 1
 OpDecorate %7 DescriptorSet 0
 OpDecorate %7 Binding 0
 OpDecorate %8 Block
@@ -38,13 +38,18 @@ OpMemberDecorate %11 0 Offset 0
 %24 = OpConstant  %4  4
 %25 = OpConstantComposite  %5  %23 %24
 %31 = OpTypePointer StorageBuffer %3
-%33 = OpConstantComposite  %3  %24 %23 %21 %20
-%38 = OpConstant  %4  6
-%39 = OpConstant  %4  7
-%40 = OpConstantComposite  %5  %38 %39
-%41 = OpConstant  %4  8
-%42 = OpConstantComposite  %6  %38 %39 %41
-%43 = OpConstant  %4  9
+%33 = OpConstant  %4  30
+%34 = OpConstant  %4  70
+%36 = OpTypePointer Function %4
+%38 = OpConstantNull  %4
+%40 = OpConstantNull  %4
+%55 = OpConstantComposite  %3  %24 %23 %21 %20
+%60 = OpConstant  %4  6
+%61 = OpConstant  %4  7
+%62 = OpConstantComposite  %5  %60 %61
+%63 = OpConstant  %4  8
+%64 = OpConstantComposite  %6  %60 %61 %63
+%65 = OpConstant  %4  9
 %14 = OpFunction  %2  None %15
 %13 = OpLabel
 %19 = OpAccessChain  %16  %10 %17
@@ -57,30 +62,54 @@ OpReturn
 OpFunctionEnd
 %30 = OpFunction  %2  None %15
 %29 = OpLabel
+%37 = OpVariable  %36  Function %38
+%41 = OpVariable  %36  Function %34
+%35 = OpVariable  %36  Function %33
+%39 = OpVariable  %36  Function %40
 %32 = OpAccessChain  %31  %7 %17
-OpBranch %34
-%34 = OpLabel
-OpStore %32 %33
+OpBranch %42
+%42 = OpLabel
+%43 = OpLoad  %4  %35
+OpStore %37 %43
+%44 = OpLoad  %4  %37
+OpStore %39 %44
+%45 = OpLoad  %4  %35
+%46 = OpLoad  %4  %37
+%47 = OpLoad  %4  %39
+%48 = OpLoad  %4  %41
+%49 = OpCompositeConstruct  %3  %45 %46 %47 %48
+%50 = OpLoad  %3  %32
+%51 = OpIAdd  %3  %50 %49
+OpStore %32 %51
 OpReturn
 OpFunctionEnd
-%36 = OpFunction  %2  None %15
-%35 = OpLabel
-%37 = OpAccessChain  %16  %10 %17
-OpBranch %44
-%44 = OpLabel
-%45 = OpLoad  %4  %37
-%46 = OpIAdd  %4  %45 %38
-OpStore %37 %46
+%53 = OpFunction  %2  None %15
+%52 = OpLabel
+%54 = OpAccessChain  %31  %7 %17
+OpBranch %56
+%56 = OpLabel
+OpStore %54 %55
 OpReturn
 OpFunctionEnd
-%48 = OpFunction  %2  None %15
-%47 = OpLabel
-%49 = OpAccessChain  %31  %7 %17
-%50 = OpAccessChain  %16  %10 %17
-OpBranch %51
-%51 = OpLabel
-%52 = OpFunctionCall  %2  %30
-%53 = OpFunctionCall  %2  %14
-%54 = OpFunctionCall  %2  %36
+%58 = OpFunction  %2  None %15
+%57 = OpLabel
+%59 = OpAccessChain  %16  %10 %17
+OpBranch %66
+%66 = OpLabel
+%67 = OpLoad  %4  %59
+%68 = OpIAdd  %4  %67 %60
+OpStore %59 %68
+OpReturn
+OpFunctionEnd
+%70 = OpFunction  %2  None %15
+%69 = OpLabel
+%71 = OpAccessChain  %31  %7 %17
+%72 = OpAccessChain  %16  %10 %17
+OpBranch %73
+%73 = OpLabel
+%74 = OpFunctionCall  %2  %53
+%75 = OpFunctionCall  %2  %14
+%76 = OpFunctionCall  %2  %58
+%77 = OpFunctionCall  %2  %30
 OpReturn
 OpFunctionEnd

tests/out/wgsl/const-exprs.wgsl

@@ -11,6 +11,25 @@ fn index_of_compose() {
     return;
 }
 
+fn non_constant_initializers() {
+    var w: i32 = 30;
+    var x: i32;
+    var y: i32;
+    var z: i32 = 70;
+
+    let _e2 = w;
+    x = _e2;
+    let _e4 = x;
+    y = _e4;
+    let _e9 = w;
+    let _e10 = x;
+    let _e11 = y;
+    let _e12 = z;
+    let _e14 = out;
+    out = (_e14 + vec4<i32>(_e9, _e10, _e11, _e12));
+    return;
+}
+
 fn swizzle_of_compose() {
     let a_1 = vec2<i32>(1, 2);
     let b_1 = vec2<i32>(3, 4);
@@ -29,5 +48,6 @@ fn main() {
     swizzle_of_compose();
     index_of_compose();
     compose_three_deep();
+    non_constant_initializers();
     return;
 }