[naga] fix the way we adjust constant initializers when processing overrides

This fixes 2 issues:
- we used to index `adjusted_global_expressions` with the handle index of the constant instead of its initializer
- we used to adjust the initializer multiple times if the arena contained multiple `Expression::Constant`s pointing to the same constant

Author: teoxoy

naga/src/back/pipeline_constants.rs

@@ -129,8 +129,10 @@ pub fn process_overrides<'a>(
                 Expression::Constant(c_h)
             }
             Expression::Constant(c_h) => {
-                adjusted_constant_initializers.insert(c_h);
-                module.constants[c_h].init = adjusted_global_expressions[c_h.index()];
+                if adjusted_constant_initializers.insert(c_h) {
+                    let init = &mut module.constants[c_h].init;
+                    *init = adjusted_global_expressions[init.index()];
+                }
                 expr
             }
             expr => expr,

naga/tests/in/spv/spec-constants-issue-5598.spv

@@ -0,0 +1,96 @@
+; SPIR-V
+; Version: 1.5
+; Generator: Google rspirv; 0
+; Bound: 68
+; Schema: 0
+               OpCapability Shader
+               OpCapability VulkanMemoryModel
+               OpMemoryModel Logical Vulkan
+               OpEntryPoint Fragment %1 "fragment" %gl_FragCoord %3
+               OpEntryPoint Vertex %4 "vertex" %gl_VertexIndex %gl_Position
+               OpExecutionMode %1 OriginUpperLeft
+               OpDecorate %gl_FragCoord BuiltIn FragCoord
+               OpDecorate %10 SpecId 100
+               OpDecorate %3 Location 0
+               OpDecorate %_arr_v4float_uint_6 ArrayStride 16
+               OpDecorate %gl_VertexIndex BuiltIn VertexIndex
+               OpDecorate %gl_Position BuiltIn Position
+               OpDecorate %gl_Position Invariant
+      %float = OpTypeFloat 32
+    %v4float = OpTypeVector %float 4
+%_ptr_Input_v4float = OpTypePointer Input %v4float
+%_ptr_Output_v4float = OpTypePointer Output %v4float
+       %void = OpTypeVoid
+         %17 = OpTypeFunction %void
+%gl_FragCoord = OpVariable %_ptr_Input_v4float Input
+       %bool = OpTypeBool
+       %uint = OpTypeInt 32 0
+         %10 = OpSpecConstant %uint 2
+     %uint_1 = OpConstant %uint 1
+    %v2float = OpTypeVector %float 2
+%_ptr_Output_float = OpTypePointer Output %float
+          %3 = OpVariable %_ptr_Output_v4float Output
+     %uint_0 = OpConstant %uint 0
+%_ptr_Input_uint = OpTypePointer Input %uint
+     %uint_6 = OpConstant %uint 6
+%_arr_v4float_uint_6 = OpTypeArray %v4float %uint_6
+%_ptr_Function__arr_v4float_uint_6 = OpTypePointer Function %_arr_v4float_uint_6
+%gl_VertexIndex = OpVariable %_ptr_Input_uint Input
+   %float_n1 = OpConstant %float -1
+    %float_0 = OpConstant %float 0
+    %float_1 = OpConstant %float 1
+         %32 = OpConstantComposite %v4float %float_n1 %float_n1 %float_0 %float_1
+         %33 = OpConstantComposite %v4float %float_1 %float_n1 %float_0 %float_1
+         %34 = OpConstantComposite %v4float %float_1 %float_1 %float_0 %float_1
+         %35 = OpConstantComposite %v4float %float_n1 %float_1 %float_0 %float_1
+         %36 = OpConstantComposite %_arr_v4float_uint_6 %32 %33 %34 %34 %35 %32
+%_ptr_Function_v4float = OpTypePointer Function %v4float
+%gl_Position = OpVariable %_ptr_Output_v4float Output
+ %float_0_25 = OpConstant %float 0.25
+  %float_0_5 = OpConstant %float 0.5
+          %1 = OpFunction %void None %17
+         %38 = OpLabel
+         %39 = OpLoad %v4float %gl_FragCoord
+         %40 = OpCompositeExtract %float %39 0
+         %41 = OpCompositeExtract %float %39 1
+         %42 = OpIEqual %bool %10 %uint_1
+               OpSelectionMerge %43 None
+               OpBranchConditional %42 %44 %45
+         %44 = OpLabel
+         %46 = OpFMul %float %40 %float_0_5
+         %47 = OpFMul %float %41 %float_0_5
+         %48 = OpCompositeConstruct %v2float %46 %47
+               OpBranch %43
+         %45 = OpLabel
+         %49 = OpFMul %float %40 %float_0_25
+         %50 = OpFMul %float %41 %float_0_25
+         %51 = OpCompositeConstruct %v2float %49 %50
+               OpBranch %43
+         %43 = OpLabel
+         %52 = OpPhi %v2float %48 %44 %51 %45
+         %53 = OpCompositeExtract %float %52 0
+         %54 = OpAccessChain %_ptr_Output_float %3 %uint_0
+               OpStore %54 %53
+         %55 = OpCompositeExtract %float %52 1
+         %56 = OpAccessChain %_ptr_Output_float %3 %uint_1
+               OpStore %56 %55
+               OpReturn
+               OpFunctionEnd
+          %4 = OpFunction %void None %17
+         %57 = OpLabel
+         %58 = OpVariable %_ptr_Function__arr_v4float_uint_6 Function
+         %59 = OpLoad %uint %gl_VertexIndex
+               OpStore %58 %36
+         %60 = OpULessThan %bool %59 %uint_6
+               OpSelectionMerge %61 None
+               OpBranchConditional %60 %62 %63
+         %62 = OpLabel
+         %64 = OpInBoundsAccessChain %_ptr_Function_v4float %58 %59
+         %65 = OpLoad %v4float %64
+               OpStore %gl_Position %65
+               OpBranch %61
+         %63 = OpLabel
+               OpBranch %61
+         %61 = OpLabel
+               OpReturn
+               OpFunctionEnd

naga/tests/in/spv/spec-constants-issue-5598.spvasm

@@ -0,0 +1,34 @@
+#version 310 es
+
+precision highp float;
+precision highp int;
+
+vec4 global = vec4(0.0);
+
+vec4 global_1 = vec4(0.0);
+
+layout(location = 0) out vec4 _fs2p_location0;
+
+void function() {
+    vec2 phi_52_ = vec2(0.0);
+    vec4 _e7 = global;
+    if (false) {
+        phi_52_ = vec2((_e7.x * 0.5), (_e7.y * 0.5));
+    } else {
+        phi_52_ = vec2((_e7.x * 0.25), (_e7.y * 0.25));
+    }
+    vec2 _e20 = phi_52_;
+    global_1[0u] = _e20.x;
+    global_1[1u] = _e20.y;
+    return;
+}
+
+void main() {
+    vec4 param = gl_FragCoord;
+    global = param;
+    function();
+    vec4 _e3 = global_1;
+    _fs2p_location0 = _e3;
+    return;
+}
+

naga/tests/out/glsl/spec-constants-issue-5598.fragment.Fragment.glsl

@@ -0,0 +1,34 @@
+#version 310 es
+
+precision highp float;
+precision highp int;
+
+uint global_2 = 0u;
+
+vec4 global_3 = vec4(0.0, 0.0, 0.0, 1.0);
+
+invariant gl_Position;
+
+void function_1() {
+    vec4 local[6] = vec4[6](vec4(0.0), vec4(0.0), vec4(0.0), vec4(0.0), vec4(0.0), vec4(0.0));
+    uint _e5 = global_2;
+    local = vec4[6](vec4(-1.0, -1.0, 0.0, 1.0), vec4(1.0, -1.0, 0.0, 1.0), vec4(1.0, 1.0, 0.0, 1.0), vec4(1.0, 1.0, 0.0, 1.0), vec4(-1.0, 1.0, 0.0, 1.0), vec4(-1.0, -1.0, 0.0, 1.0));
+    if ((_e5 < 6u)) {
+        vec4 _e8 = local[_e5];
+        global_3 = _e8;
+    }
+    return;
+}
+
+void main() {
+    uint param_1 = uint(gl_VertexID);
+    global_2 = param_1;
+    function_1();
+    float _e4 = global_3.y;
+    global_3.y = -(_e4);
+    vec4 _e6 = global_3;
+    gl_Position = _e6;
+    gl_Position.yz = vec2(-gl_Position.y, gl_Position.z * 2.0 - gl_Position.w);
+    return;
+}
+

naga/tests/out/glsl/spec-constants-issue-5598.vertex.Vertex.glsl

@@ -973,6 +973,7 @@ fn convert_spv_all() {
     );
     convert_spv("builtin-accessed-outside-entrypoint", true, Targets::WGSL);
     convert_spv("spec-constants", true, Targets::IR);
+    convert_spv("spec-constants-issue-5598", true, Targets::GLSL);
     convert_spv(
         "subgroup-operations-s",
         false,