Disallow arrays and structs from becoming loop variables.

Fixes awkward code-gen issue.

reference/opt/shaders-hlsl/frag/array-lut-no-loop-variable.frag

@@ -0,0 +1,32 @@
+static const float _17[5] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f };
+
+static float4 FragColor;
+static float4 v0;
+
+struct SPIRV_Cross_Input
+{
+    float4 v0 : TEXCOORD0;
+};
+
+struct SPIRV_Cross_Output
+{
+    float4 FragColor : SV_Target0;
+};
+
+void frag_main()
+{
+    float lut[5] = _17;
+    int _33;
+    for (int _46 = 0; _46 < 4; _33 = _46 + 1, FragColor += lut[_33].xxxx, _46 = _33)
+    {
+    }
+}
+
+SPIRV_Cross_Output main(SPIRV_Cross_Input stage_input)
+{
+    v0 = stage_input.v0;
+    frag_main();
+    SPIRV_Cross_Output stage_output;
+    stage_output.FragColor = FragColor;
+    return stage_output;
+}

reference/opt/shaders-msl/frag/array-lut-no-loop-variable.frag

@@ -0,0 +1,39 @@
+#pragma clang diagnostic ignored "-Wmissing-prototypes"
+
+#include <metal_stdlib>
+#include <simd/simd.h>
+
+using namespace metal;
+
+constant float _17[5] = {1.0, 2.0, 3.0, 4.0, 5.0};
+
+struct main0_out
+{
+    float4 FragColor [[color(0)]];
+};
+
+// Implementation of an array copy function to cover GLSL's ability to copy an array via assignment.
+template<typename T, uint N>
+void spvArrayCopy(thread T (&dst)[N], thread const T (&src)[N])
+{
+    for (uint i = 0; i < N; dst[i] = src[i], i++);
+}
+
+// An overload for constant arrays.
+template<typename T, uint N>
+void spvArrayCopyConstant(thread T (&dst)[N], constant T (&src)[N])
+{
+    for (uint i = 0; i < N; dst[i] = src[i], i++);
+}
+
+fragment main0_out main0()
+{
+    main0_out out = {};
+    float lut[5] = {1.0, 2.0, 3.0, 4.0, 5.0};
+    int _33;
+    for (int _46 = 0; _46 < 4; _33 = _46 + 1, out.FragColor += float4(lut[_33]), _46 = _33)
+    {
+    }
+    return out;
+}
+

reference/opt/shaders/frag/array-lut-no-loop-variable.frag

@@ -0,0 +1,15 @@
+#version 310 es
+precision mediump float;
+precision highp int;
+
+layout(location = 0) out vec4 FragColor;
+
+void main()
+{
+    float lut[5] = float[](1.0, 2.0, 3.0, 4.0, 5.0);
+    mediump int _33;
+    for (int _46 = 0; _46 < 4; _33 = _46 + 1, FragColor += vec4(lut[_33]), _46 = _33)
+    {
+    }
+}
+

reference/shaders-hlsl/frag/array-lut-no-loop-variable.frag

@@ -0,0 +1,31 @@
+static const float _17[5] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f };
+
+static float4 FragColor;
+static float4 v0;
+
+struct SPIRV_Cross_Input
+{
+    float4 v0 : TEXCOORD0;
+};
+
+struct SPIRV_Cross_Output
+{
+    float4 FragColor : SV_Target0;
+};
+
+void frag_main()
+{
+    float lut[5] = _17;
+    for (int i = 0; i < 4; i++, FragColor += lut[i].xxxx)
+    {
+    }
+}
+
+SPIRV_Cross_Output main(SPIRV_Cross_Input stage_input)
+{
+    v0 = stage_input.v0;
+    frag_main();
+    SPIRV_Cross_Output stage_output;
+    stage_output.FragColor = FragColor;
+    return stage_output;
+}

reference/shaders-msl/frag/array-lut-no-loop-variable.frag

@@ -0,0 +1,38 @@
+#pragma clang diagnostic ignored "-Wmissing-prototypes"
+
+#include <metal_stdlib>
+#include <simd/simd.h>
+
+using namespace metal;
+
+constant float _17[5] = {1.0, 2.0, 3.0, 4.0, 5.0};
+
+struct main0_out
+{
+    float4 FragColor [[color(0)]];
+};
+
+// Implementation of an array copy function to cover GLSL's ability to copy an array via assignment.
+template<typename T, uint N>
+void spvArrayCopy(thread T (&dst)[N], thread const T (&src)[N])
+{
+    for (uint i = 0; i < N; dst[i] = src[i], i++);
+}
+
+// An overload for constant arrays.
+template<typename T, uint N>
+void spvArrayCopyConstant(thread T (&dst)[N], constant T (&src)[N])
+{
+    for (uint i = 0; i < N; dst[i] = src[i], i++);
+}
+
+fragment main0_out main0()
+{
+    main0_out out = {};
+    float lut[5] = {1.0, 2.0, 3.0, 4.0, 5.0};
+    for (int i = 0; i < 4; i++, out.FragColor += float4(lut[i]))
+    {
+    }
+    return out;
+}
+

reference/shaders/frag/array-lut-no-loop-variable.frag

@@ -0,0 +1,14 @@
+#version 310 es
+precision mediump float;
+precision highp int;
+
+layout(location = 0) out vec4 FragColor;
+
+void main()
+{
+    float lut[5] = float[](1.0, 2.0, 3.0, 4.0, 5.0);
+    for (mediump int i = 0; i < 4; i++, FragColor += vec4(lut[i]))
+    {
+    }
+}
+

shaders-hlsl/frag/array-lut-no-loop-variable.frag

@@ -0,0 +1,13 @@
+#version 310 es
+precision mediump float;
+
+layout(location = 0) out vec4 FragColor;
+layout(location = 0) in vec4 v0;
+
+void main()
+{
+	float lut[5] = float[](1.0, 2.0, 3.0, 4.0, 5.0);
+	for (int i = 0; i < 4; i++, FragColor += lut[i])
+	{
+	}
+}

shaders-msl/frag/array-lut-no-loop-variable.frag

@@ -0,0 +1,13 @@
+#version 310 es
+precision mediump float;
+
+layout(location = 0) out vec4 FragColor;
+layout(location = 0) in vec4 v0;
+
+void main()
+{
+	float lut[5] = float[](1.0, 2.0, 3.0, 4.0, 5.0);
+	for (int i = 0; i < 4; i++, FragColor += lut[i])
+	{
+	}
+}

shaders/frag/array-lut-no-loop-variable.frag

@@ -0,0 +1,13 @@
+#version 310 es
+precision mediump float;
+
+layout(location = 0) out vec4 FragColor;
+layout(location = 0) in vec4 v0;
+
+void main()
+{
+	float lut[5] = float[](1.0, 2.0, 3.0, 4.0, 5.0);
+	for (int i = 0; i < 4; i++, FragColor += lut[i])
+	{
+	}
+}

spirv_cross.cpp

@@ -3679,7 +3679,8 @@ void Compiler::analyze_variable_scope(SPIRFunction &entry)
 				// so we will have to lift the dominator up to the relevant loop header instead.
 				builder.add_block(this->continue_block_to_loop_header[block]);
 
-				if (type.vecsize == 1 && type.columns == 1)
+				// Arrays or structs cannot be loop variables.
+				if (type.vecsize == 1 && type.columns == 1 && type.basetype != SPIRType::Struct && type.array.empty())
 				{
 					// The variable is used in multiple continue blocks, this is not a loop
 					// candidate, signal that by setting block to -1u.

spirv_glsl.cpp

@@ -8573,7 +8573,7 @@ string CompilerGLSL::emit_for_loop_initializers(const SPIRBlock &block)
 				if (expr.empty())
 				{
 					// For loop initializers are of the form <type id = value, id = value, id = value, etc ...
-					auto &var = get<SPIRVariable>(block.loop_variables.front());
+					auto &var = get<SPIRVariable>(loop_var);
 					auto &type = get<SPIRType>(var.basetype);
 					expr = join(to_qualifiers_glsl(var.self), type_to_glsl(type), " ");
 				}