[Port] [6000.0] Use builtin firstbitlow with DXC

svc-reach-platform-support · Evergreen · commit bac51be8f3cd · 2026-02-20T14:05:06.000Z
diff --git a/Packages/com.unity.render-pipelines.universal/ShaderLibrary/ShaderVariablesFunctions.hlsl b/Packages/com.unity.render-pipelines.universal/ShaderLibrary/ShaderVariablesFunctions.hlsl
@@ -495,7 +495,8 @@ 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
`@@ -495,7 +495,8 @@ uint Select4(uint4 v, uint i)`
`495`	`495`	`(((v.y & mask0) \| (v.x & ~mask0)) & ~mask1);`
`496`	`496`	`}`
`497`	`497`
`498`		`-#if SHADER_TARGET < 45`
	`498`	`+#if SHADER_TARGET < 45 && !defined UNITY_COMPILER_DXC`
	`499`	`+// Workaround is only technically required for GL Core <4.0 and GLES <3.1`
`499`	`500`	`uint URP_FirstBitLow(uint m)`
`500`	`501`	`{`
`501`	`502`	`// http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightFloatCast`