Optimize for a dumb compiler (need to profile)

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.hlsl

 // we need to push the shading position back to avoid self-shadowing problems.
 float3 ComputeThicknessDisplacement(BSDFData bsdfData, float3 L, float NdotL)
 {
-    // Compute the thickness in world units along the normal.
-    float thicknessInMeters = bsdfData.thickness * METERS_PER_MILLIMETER;
-    float thicknessInUnits  = thicknessInMeters * _WorldScales[bsdfData.subsurfaceProfile].y;
+    float displacement = 0;
+
+    [flatten] if (bsdfData.useThickObjectMode && NdotL < 0)
+    {
+        // Compute the thickness in world units along the normal.
+        float thicknessInMeters = bsdfData.thickness * METERS_PER_MILLIMETER;
+        float thicknessInUnits  = thicknessInMeters * _WorldScales[bsdfData.subsurfaceProfile].y;
-    // Compute the thickness in world units along the light vector.
-    float unprojectedThickness = thicknessInUnits / -NdotL;
+        // Compute the thickness in world units along the light vector.
+        displacement = thicknessInUnits / -NdotL;
+    }
-    return unprojectedThickness * L;
+    return displacement * L;
 }
 
 // Currently, we only model diffuse transmission. Specular transmission is not yet supported.
     float3 L     = -lightData.forward; // Lights point backward in Unity
     float  NdotL = dot(N, L);
 
-    [flatten] if (bsdfData.useThickObjectMode && NdotL < 0)
-    {
-        posInput.positionWS += ComputeThicknessDisplacement(bsdfData, L, NdotL);
-    }
+    posInput.positionWS += ComputeThicknessDisplacement(bsdfData, L, NdotL);
 
     float3 color; float attenuation;
     EvaluateLight_Directional(lightLoopContext, posInput, lightData, bakeLightingData, N, L,
 
-    [branch] if (intensity > 0.0)
+    [branch] if (intensity > 0)
     {
         BSDF(V, L, posInput.positionWS, preLightData, bsdfData, lighting.diffuse, lighting.specular);
 
 
-    [flatten] if (bsdfData.enableTransmission)
+    [branch] if (bsdfData.enableTransmission)
     {
         // We use diffuse lighting for accumulation since it is going to be blurred during the SSS pass.
         lighting.diffuse += EvaluateTransmission(bsdfData, NdotL, preLightData.NdotV, attenuation * lightData.diffuseScale);
     float3 L       = unL * distRcp;
     float  NdotL   = dot(N, L);
 
-    [flatten] if (bsdfData.useThickObjectMode && NdotL < 0)
-    {
-        posInput.positionWS += ComputeThicknessDisplacement(bsdfData, L, NdotL);
-    }
+    posInput.positionWS += ComputeThicknessDisplacement(bsdfData, L, NdotL);
 
     float3 color; float attenuation;
     EvaluateLight_Punctual(lightLoopContext, posInput, lightData, bakeLightingData, N, L, dist, distSq,
 
-    [branch] if (intensity > 0.0)
+    [branch] if (intensity > 0)
     {
         // Simulate a sphere light with this hack.
         bsdfData.roughnessT = max(bsdfData.roughnessT, lightData.minRoughness);
         lighting.specular *= intensity * lightData.specularScale;
     }
 
-    [flatten] if (bsdfData.enableTransmission)
+    [branch] if (bsdfData.enableTransmission)
     {
         // We use diffuse lighting for accumulation since it is going to be blurred during the SSS pass.
         lighting.diffuse += EvaluateTransmission(bsdfData, NdotL, preLightData.NdotV, attenuation * lightData.diffuseScale);