Fix GLSL translation of several Texture* operations (#800)

A user found that the `Texture2D<float2>.Load(...)` operation was not being compiled to GLSL properly, such that it returned a `vec4` instead of the expected `vec2`.

The GLSL texture-related functions always return (and take) 4-component vectors, and we already have infrastructure in `emit.cpp` for recognizing a `$z` operator in the GLSL intrinsic definition to stand in for an appropriate swizzle based on teh number of components in the texture result type.

This change just adds that `$z` operator to the GLSL code for several more texture operations (including `Load()`) that are defined on a `Texture*<T>` and that return `T`.

This change doesn't try to add additional GLSL translations for texture-related operations (e.g., additional variations like `SampleCmp` that we have defined in the stdlib but not given GLSL translations for). That work still needs to be done.

2 files changed, 65 insertions, 0 deletions

diff --git a/tests/cross-compile/texture-load.slang b/tests/cross-compile/texture-load.slang
new file mode 100644
index 000000000..71f22b13a
--- /dev/null
+++ b/tests/cross-compile/texture-load.slang
@@ -0,0 +1,21 @@
+// texture-load.slang
+
+// Confirm that texture `Load` operations yield the
+// expected type when compiled to SPIR-V.
+
+//TEST:CROSS_COMPILE:-target spirv-assembly -entry main -stage compute
+
+Texture2D<float2>   inputTexture;
+RWTexture2D<float2> outputTexture;
+
+cbuffer C
+{
+	int2 pos;
+}
+
+[numthreads(16, 16, 1)]
+void main(uint2 pixelIndex : SV_DispatchThreadID)
+{
+	float2 tmp = inputTexture.Load(int3(pos,0));
+    outputTexture[pos] = tmp;
+}
diff --git a/tests/cross-compile/texture-load.slang.glsl b/tests/cross-compile/texture-load.slang.glsl
new file mode 100644
index 000000000..23646db91
--- /dev/null
+++ b/tests/cross-compile/texture-load.slang.glsl
@@ -0,0 +1,44 @@
+// texture-load.slang.glsl
+//TEST_IGNORE_FILE:
+
+#version 450
+
+layout(row_major) uniform;
+layout(row_major) buffer;
+
+#extension GL_EXT_samplerless_texture_functions : require
+
+struct SLANG_ParameterGroup_C_0
+{
+    ivec2 pos_0;
+};
+
+layout(binding = 2)
+layout(std140)
+uniform _S1
+{
+    SLANG_ParameterGroup_C_0 _data;
+} C_0;
+
+layout(binding = 0)
+uniform texture2D inputTexture_0;
+
+layout(rg32f)
+layout(binding = 1)
+uniform image2D outputTexture_0;
+
+layout(local_size_x = 16, local_size_y = 16, local_size_z = 1) in;
+void main()
+{
+    vec2 tmp_0 = texelFetch(
+    	inputTexture_0,
+    	ivec3(C_0._data.pos_0, 0).xy,
+    	ivec3(C_0._data.pos_0, 0).z).xy;
+
+    imageStore(
+    	outputTexture_0,
+    	ivec2(uvec2(C_0._data.pos_0)),
+    	vec4(tmp_0, float(0), float(0)));
+
+    return;
+}