Add a compile-time loop construct to Slang

The basic syntax is:

    $for(i in Range(0,99))
    {
       /* stuff goes here */
    }

Note that the exact form is very restrictive. All that you are allowed to change is `i`, `0`, `99` or `/* stuff goes here */`.

As a tiny bit of syntax sugar, the following should work:

    $for(i in Range(99))
    {
       /* stuff goes here */
    }

Note that the range given is half-open (C++ iterator `[begin,end)` style).
Both the beginning and end of the range must be compile-time constant expressions that Slang knows how to constant-fold.

The implementation will basically generate code for `/* stuff goes here */` N times, once for each value in the half-open range.
Each time, the variable `i` will be replaced with a different compile-time-constant expression.

While I was working on a test case for this, I also found that our build of glslang had an issue with resource limits, so I fixed that.
Clients will need to build a new glslang to use the fix.

2 files changed, 47 insertions, 0 deletions

diff --git a/tests/cross-compile/compile-time-loop.slang b/tests/cross-compile/compile-time-loop.slang
new file mode 100644
index 000000000..aae35f09e
--- /dev/null
+++ b/tests/cross-compile/compile-time-loop.slang
@@ -0,0 +1,14 @@
+//TEST:CROSS_COMPILE: -profile ps_5_0 -entry main -target spirv-assembly
+
+Texture2D t;
+SamplerState s;
+
+float4 main(float2 uv) : SV_Target
+{
+	float4 result = 0;
+	$for(i in Range(0,5))
+	{
+		result += t.Sample(s, uv, int2(i - 2, 0));
+	}
+	return result;
+}
diff --git a/tests/cross-compile/compile-time-loop.slang.glsl b/tests/cross-compile/compile-time-loop.slang.glsl
new file mode 100644
index 000000000..a1f87be65
--- /dev/null
+++ b/tests/cross-compile/compile-time-loop.slang.glsl
@@ -0,0 +1,33 @@
+//TEST_IGNORE_FILE:
+
+layout(binding = 0)
+uniform texture2D t;
+
+layout(binding = 1)
+uniform sampler s;
+
+vec4 main_(vec2 uv)
+{
+	vec4 result = vec4(0);
+
+	result += textureOffset(sampler2D(t,s), uv, ivec2(0 - 2, 0));
+	result += textureOffset(sampler2D(t,s), uv, ivec2(1 - 2, 0));
+	result += textureOffset(sampler2D(t,s), uv, ivec2(2 - 2, 0));
+	result += textureOffset(sampler2D(t,s), uv, ivec2(3 - 2, 0));
+	result += textureOffset(sampler2D(t,s), uv, ivec2(4 - 2, 0));
+
+	return result;
+}
+
+layout(location = 0)
+in vec2 SLANG_in_uv;
+
+layout(location = 0)
+out vec4 SLANG_out_main_result;
+
+void main()
+{
+	vec2 uv = SLANG_in_uv;
+	vec4 main_result = main_(uv);
+	SLANG_out_main_result = main_result;
+}
\ No newline at end of file