From 83675103a1a4fefde11b314aed26f4d37860efe7 Mon Sep 17 00:00:00 2001
From: davli-nv <davli@nvidia.com>
Date: Tue, 5 Aug 2025 10:55:52 -0700
Subject: Implement SPV_EXT_fragment_invocation_density (SPV_NV_shading_rate)
 (#8037)

* Implement SPV_EXT_fragment_invocation_density

-Adds semantics SV_FragSize and SV_FragInvocationCount and implements them for SPIRV and GLSL using the appropriate target builtins from extensions.
-Adds test case checking for expected target builtins from these semantics.
-For future work, could implement SV_FragSize using pixel shader input SV_ShadingRate for HLSL, and SV_FragInvocationCount needs research.

Fixes #7974

Generated with Claude Code

* address review feedback

https://github.com/shader-slang/slang/pull/8037#pullrequestreview-3084645845

* fixup format

* review feedback

https://github.com/shader-slang/slang/pull/8037#pullrequestreview-3086442819
---
 tests/glsl/fragment-invocation-density-glsl.slang | 15 ++++++++++++++
 tests/spirv/fragment-invocation-density.slang     | 25 +++++++++++++++++++++++
 2 files changed, 40 insertions(+)
 create mode 100644 tests/glsl/fragment-invocation-density-glsl.slang
 create mode 100644 tests/spirv/fragment-invocation-density.slang

(limited to 'tests')

diff --git a/tests/glsl/fragment-invocation-density-glsl.slang b/tests/glsl/fragment-invocation-density-glsl.slang
new file mode 100644
index 000000000..7cee4620b
--- /dev/null
+++ b/tests/glsl/fragment-invocation-density-glsl.slang
@@ -0,0 +1,15 @@
+//TEST:SIMPLE(filecheck=CHECK-GLSL): -target glsl -stage fragment -entry main
+
+// Test for EXT_fragment_invocation_density support (gl_FragSizeEXT and gl_FragInvocationCountEXT )
+import glsl;
+
+layout(location = 0) out highp vec4 FragColor;
+
+void main()
+{
+    // CHECK-GLSL: #extension GL_EXT_fragment_invocation_density : require
+    // CHECK-GLSL-DAG: gl_FragSizeEXT
+    // CHECK-GLSL-DAG: gl_FragInvocationCountEXT
+
+    FragColor = vec4(gl_FragSizeEXT.x, gl_FragSizeEXT.y, gl_FragInvocationCountEXT, 1.0);
+}
\ No newline at end of file
diff --git a/tests/spirv/fragment-invocation-density.slang b/tests/spirv/fragment-invocation-density.slang
new file mode 100644
index 000000000..f26b403ec
--- /dev/null
+++ b/tests/spirv/fragment-invocation-density.slang
@@ -0,0 +1,25 @@
+//TEST:SIMPLE(filecheck=CHECK-SPIRV): -target spirv -stage fragment -entry main
+//TEST:SIMPLE(filecheck=CHECK-GLSL): -target glsl -stage fragment -entry main
+
+// Test for SPV_EXT_fragment_invocation_density support (SV_FragSize and SV_FragInvocationCount)
+
+struct FragmentInput
+{
+    int2 fragmentSize : SV_FragSize;
+    int invocationsPerPixel : SV_FragInvocationCount;
+}
+
+[shader("fragment")]
+float4 main(FragmentInput input) : SV_Target
+{
+    // CHECK-SPIRV: OpCapability FragmentDensityEXT
+    // CHECK-SPIRV: OpExtension "SPV_EXT_fragment_invocation_density"
+    // CHECK-SPIRV-DAG: OpDecorate {{.*}} BuiltIn FragSizeEXT
+    // CHECK-SPIRV-DAG: OpDecorate {{.*}} BuiltIn FragInvocationCountEXT
+
+    // CHECK-GLSL: #extension GL_EXT_fragment_invocation_density : require
+    // CHECK-GLSL-DAG: gl_FragSizeEXT
+    // CHECK-GLSL-DAG: gl_FragInvocationCountEXT
+
+    return float4(input.fragmentSize.x, input.fragmentSize.y, input.invocationsPerPixel, 1.0);
+}
\ No newline at end of file
-- 
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