Don't emitting an imported declaration unless it is used.

This helps avoid the problem where we emit a function that does a `discard` and thus get a GLSL compilation failure in a vertex shader (that doesn't even call the function).

2 files changed, 178 insertions, 0 deletions

diff --git a/tests/render/unused-discard.hlsl b/tests/render/unused-discard.hlsl
new file mode 100644
index 000000000..dad2f78e3
--- /dev/null
+++ b/tests/render/unused-discard.hlsl
@@ -0,0 +1,151 @@
+//TEST(smoke,render):COMPARE_HLSL_GLSL_RENDER:
+
+// This is a basic test case for cross-compilation behavior.
+//
+// We will define distinct HLSL and GLSL entry points,
+// but the two will share a dependency on a file of
+// pure Spire code that provides the actual shading logic.
+
+
+// Pull in Spire code depdendency using extended syntax:
+__import unused_discard;
+
+#if defined(__HLSL__)
+
+cbuffer Uniforms
+{
+	float4x4 modelViewProjection;
+};
+
+struct AssembledVertex
+{
+	float3	position;
+	float3	color;
+};
+
+struct CoarseVertex
+{
+	float3	color;
+};
+
+struct Fragment
+{
+	float4 color;
+};
+
+// Vertex  Shader
+
+struct VertexStageInput
+{
+	AssembledVertex assembledVertex	: A;
+};
+
+struct VertexStageOutput
+{
+	CoarseVertex	coarseVertex	: CoarseVertex;
+	float4			sv_position		: SV_Position;
+};
+
+VertexStageOutput vertexMain(VertexStageInput input)
+{
+	VertexStageOutput output;
+
+	float3 position = input.assembledVertex.position;
+	float3 color	= input.assembledVertex.color;
+
+	output.coarseVertex.color = color;
+	output.sv_position = mul(modelViewProjection, float4(position, 1.0));
+
+	return output;
+	
+}
+
+// Fragment Shader
+
+struct FragmentStageInput
+{
+	CoarseVertex	coarseVertex	: CoarseVertex;
+};
+
+struct FragmentStageOutput
+{
+	Fragment fragment	: SV_Target;
+};
+
+FragmentStageOutput fragmentMain(FragmentStageInput input)
+{
+	FragmentStageOutput output;
+
+	float3 color = input.coarseVertex.color;
+
+	color = transformColor(color);
+
+	doConditionalDiscard(color);
+
+	output.fragment.color = float4(color, 1.0);
+
+	return output;
+}
+
+#elif defined(__GLSL__)
+
+#version 420
+
+uniform Uniforms
+{
+	mat4x4 modelViewProjection;
+};
+
+#define ASSEMBLED_VERTEX(QUAL)		\
+	/* */
+
+#define V2F(QUAL)									\
+	layout(location = 0) QUAL vec3 coarse_color;	\
+	/* */
+
+// Vertex  Shader
+
+#ifdef __GLSL_VERTEX__
+
+layout(location = 0)
+in vec3 assembled_position;
+
+layout(location = 1)
+in vec3 assembled_color;
+
+V2F(out)
+
+void main()
+{
+	vec3 position = assembled_position;
+	vec3 color	= assembled_color;
+
+	coarse_color = color;
+//	gl_Position = modelViewProjection * vec4(position, 1.0);
+	gl_Position = vec4(position, 1.0) * modelViewProjection;
+}
+
+#endif
+
+#ifdef __GLSL_FRAGMENT__
+
+V2F(in)
+
+layout(location = 0)
+out vec4 fragment_color;
+
+void main()
+{
+	vec3 color = coarse_color;
+
+	color = transformColor(color);
+
+	doConditionalDiscard(color);
+
+	fragment_color = vec4(color, 1.0);
+}
+
+
+#endif
+
+#endif
diff --git a/tests/render/unused-discard.slang b/tests/render/unused-discard.slang
new file mode 100644
index 000000000..034735840
--- /dev/null
+++ b/tests/render/unused-discard.slang
@@ -0,0 +1,27 @@
+//TEST_IGNORE_FILE:
+
+// This file implements the "library" code
+// that both the HLSL and GLSL shaders share.
+//
+// This code is written in Slang (more or less
+// just HLSL), and will be translated as needed
+// for each of the targets.
+
+float3 transformColor(float3 color)
+{
+	float3 result;
+
+	result.x = sin(20.0 * (color.x + color.y));
+	result.y = saturate(cos(color.z * 30.0));
+	result.z = sin(color.x * color.y * color.z * 100.0);
+
+	result = 0.5 * (result + 1);
+
+	return result;
+}
+
+void doConditionalDiscard(float3 color)
+{
+	if(color.x < 0.5)
+		discard;
+}