[Port] [6000.3] Use builtin firstbitlow with DXC

svc-reach-platform-support · Evergreen · commit 570c539a62ac · 2026-02-20T09:48:06.000Z
diff --git a/Packages/com.unity.render-pipelines.universal/ShaderLibrary/ShaderVariablesFunctions.hlsl b/Packages/com.unity.render-pipelines.universal/ShaderLibrary/ShaderVariablesFunctions.hlsl
@@ -591,7 +591,8 @@ uint Select4(uint4 v, uint i)
         (((v.y & mask0) | (v.x & ~mask0)) & ~mask1);
 }
 
-#if SHADER_TARGET < 45
+#if SHADER_TARGET < 45 && !defined UNITY_COMPILER_DXC
+// Workaround is only technically required for GL Core <4.0 and GLES <3.1
 uint URP_FirstBitLow(uint m)
 {
     // http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightFloatCast

Original file line number	Diff line number	Diff line change
`@@ -591,7 +591,8 @@ uint Select4(uint4 v, uint i)`
`591`	`591`	`(((v.y & mask0) \| (v.x & ~mask0)) & ~mask1);`
`592`	`592`	`}`
`593`	`593`
`594`		`-#if SHADER_TARGET < 45`
	`594`	`+#if SHADER_TARGET < 45 && !defined UNITY_COMPILER_DXC`
	`595`	`+// Workaround is only technically required for GL Core <4.0 and GLES <3.1`
`595`	`596`	`uint URP_FirstBitLow(uint m)`
`596`	`597`	`{`
`597`	`598`	`// http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightFloatCast`