Declare specialization constants in HLSL.

reference/shaders-hlsl/frag/spec-constant.frag

@@ -0,0 +1,77 @@
+const float a = 1.0f;
+const float b = 2.0f;
+const int c = 3;
+const int d = 4;
+const uint e = 5u;
+const uint f = 6u;
+const bool g = false;
+const bool h = true;
+
+struct Foo
+{
+    float elems[(d + 2)];
+};
+
+static float4 FragColor;
+
+struct SPIRV_Cross_Output
+{
+    float4 FragColor : SV_Target0;
+};
+
+void frag_main()
+{
+    float t0 = a;
+    float t1 = b;
+    uint c0 = (uint(c) + 0u);
+    int c1 = (-c);
+    int c2 = (~c);
+    int c3 = (c + d);
+    int c4 = (c - d);
+    int c5 = (c * d);
+    int c6 = (c / d);
+    uint c7 = (e / f);
+    int c8 = (c % d);
+    uint c9 = (e % f);
+    int c10 = (c >> d);
+    uint c11 = (e >> f);
+    int c12 = (c << d);
+    int c13 = (c | d);
+    int c14 = (c ^ d);
+    int c15 = (c & d);
+    bool c16 = (g || h);
+    bool c17 = (g && h);
+    bool c18 = (!g);
+    bool c19 = (g == h);
+    bool c20 = (g != h);
+    bool c21 = (c == d);
+    bool c22 = (c != d);
+    bool c23 = (c < d);
+    bool c24 = (e < f);
+    bool c25 = (c > d);
+    bool c26 = (e > f);
+    bool c27 = (c <= d);
+    bool c28 = (e <= f);
+    bool c29 = (c >= d);
+    bool c30 = (e >= f);
+    int c31 = c8 + c3;
+    int c32 = int(e + 0u);
+    bool c33 = (c != int(0u));
+    bool c34 = (e != 0u);
+    int c35 = int(g);
+    uint c36 = uint(g);
+    float c37 = float(g);
+    float _113 = t0 + t1;
+    float vec0[(c + 3)][8];
+    float vec1[(c + 2)];
+    Foo foo;
+    FragColor = ((float4(_113, _113, _113, _113) + float4(vec0[0][0], vec0[0][0], vec0[0][0], vec0[0][0])) + float4(vec1[0], vec1[0], vec1[0], vec1[0])) + float4(foo.elems[c], foo.elems[c], foo.elems[c], foo.elems[c]);
+}
+
+SPIRV_Cross_Output main()
+{
+    frag_main();
+    SPIRV_Cross_Output stage_output;
+    stage_output.FragColor = FragColor;
+    return stage_output;
+}

shaders-hlsl/frag/spec-constant.frag

@@ -0,0 +1,77 @@
+#version 310 es
+precision mediump float;
+
+layout(location = 0) out vec4 FragColor;
+layout(constant_id = 1) const float a = 1.0;
+layout(constant_id = 2) const float b = 2.0;
+layout(constant_id = 3) const int c = 3;
+layout(constant_id = 4) const int d = 4;
+layout(constant_id = 5) const uint e = 5u;
+layout(constant_id = 6) const uint f = 6u;
+layout(constant_id = 7) const bool g = false;
+layout(constant_id = 8) const bool h = true;
+// glslang doesn't seem to support partial spec constants or composites yet, so only test the basics.
+
+struct Foo
+{
+	float elems[d + 2];
+};
+
+void main()
+{
+	float t0 = a;
+	float t1 = b;
+
+	uint c0 = uint(c); // OpIAdd with different types.
+	// FConvert, float-to-double.
+	int c1 = -c; // SNegate
+	int c2 = ~c; // OpNot
+	int c3 = c + d; // OpIAdd
+	int c4 = c - d; // OpISub
+	int c5 = c * d; // OpIMul
+	int c6 = c / d; // OpSDiv
+	uint c7 = e / f; // OpUDiv
+	int c8 = c % d; // OpSMod
+	uint c9 = e % f; // OpUMod
+	// TODO: OpSRem, any way to access this in GLSL?
+	int c10 = c >> d; // OpShiftRightArithmetic
+	uint c11 = e >> f; // OpShiftRightLogical
+	int c12 = c << d; // OpShiftLeftLogical
+	int c13 = c | d; // OpBitwiseOr
+	int c14 = c ^ d; // OpBitwiseXor
+	int c15 = c & d; // OpBitwiseAnd
+	// VectorShuffle, CompositeExtract, CompositeInsert, not testable atm.
+	bool c16 = g || h; // OpLogicalOr
+	bool c17 = g && h; // OpLogicalAnd
+	bool c18 = !g; // OpLogicalNot
+	bool c19 = g == h; // OpLogicalEqual
+	bool c20 = g != h; // OpLogicalNotEqual
+	// OpSelect not testable atm.
+	bool c21 = c == d; // OpIEqual
+	bool c22 = c != d; // OpINotEqual
+	bool c23 = c < d; // OpSLessThan
+	bool c24 = e < f; // OpULessThan
+	bool c25 = c > d; // OpSGreaterThan
+	bool c26 = e > f; // OpUGreaterThan
+	bool c27 = c <= d; // OpSLessThanEqual
+	bool c28 = e <= f; // OpULessThanEqual
+	bool c29 = c >= d; // OpSGreaterThanEqual
+	bool c30 = e >= f; // OpUGreaterThanEqual
+	// OpQuantizeToF16 not testable atm.
+
+	int c31 = c8 + c3;
+
+	int c32 = int(e); // OpIAdd with different types.
+	bool c33 = bool(c); // int -> bool
+	bool c34 = bool(e); // uint -> bool
+	int c35 = int(g); // bool -> int
+	uint c36 = uint(g); // bool -> uint
+	float c37 = float(g); // bool -> float
+
+	// Flexible sized arrays with spec constants and spec constant ops.
+	float vec0[c + 3][8];
+	float vec1[c + 2];
+
+	Foo foo;
+	FragColor = vec4(t0 + t1) + vec0[0][0] + vec1[0] + foo.elems[c];
+}

spirv_hlsl.cpp

@@ -583,10 +583,35 @@ void CompilerHLSL::emit_builtin_variables()
 	}
 }
 
+void CompilerHLSL::emit_specialization_constants()
+{
+	bool emitted = false;
+	for (auto &id : ids)
+	{
+		if (id.get_type() == TypeConstant)
+		{
+			auto &c = id.get<SPIRConstant>();
+			if (!c.specialization)
+				continue;
+
+			auto &type = get<SPIRType>(c.constant_type);
+			auto name = to_name(c.self);
+
+			statement("const ", variable_decl(type, name), " = ", constant_expression(c), ";");
+			emitted = true;
+		}
+	}
+
+	if (emitted)
+		statement("");
+}
+
 void CompilerHLSL::emit_resources()
 {
 	auto &execution = get_entry_point();
 
+	emit_specialization_constants();
+
 	// Output all basic struct types which are not Block or BufferBlock as these are declared inplace
 	// when such variables are instantiated.
 	for (auto &id : ids)

spirv_hlsl.hpp

@@ -80,6 +80,7 @@ private:
 	void emit_uniform(const SPIRVariable &var) override;
 	void emit_modern_uniform(const SPIRVariable &var);
 	void emit_legacy_uniform(const SPIRVariable &var);
+	void emit_specialization_constants();
 	std::string layout_for_member(const SPIRType &type, uint32_t index) override;
 	std::string to_interpolation_qualifiers(uint64_t flags) override;
 	std::string bitcast_glsl_op(const SPIRType &result_type, const SPIRType &argument_type) override;