Rename _DECALS_3RT to DECALS_3RT and lower variant count

com.unity.render-pipelines.high-definition/HDRP/Editor/Material/BaseShaderPreprocessor.cs

             m_TileLighting = new ShaderKeyword("USE_FPTL_LIGHTLIST");
             m_ClusterLighting = new ShaderKeyword("USE_CLUSTERED_LIGHTLIST");
             m_LodFadeCrossFade = new ShaderKeyword("LOD_FADE_CROSSFADE");
-            m_Decals3RT = new ShaderKeyword("_DECALS_3RT");
-            m_Decals4RT = new ShaderKeyword("_DECALS_4RT");
+            m_Decals3RT = new ShaderKeyword("DECALS_3RT");
+            m_Decals4RT = new ShaderKeyword("DECALS_4RT");
         }
 
         public virtual void AddStripperFuncs(Dictionary<string, VariantStrippingFunc> stripperFuncs) {}

com.unity.render-pipelines.high-definition/HDRP/Material/LayeredLit/LayeredLit.shader

     // enable dithering LOD crossfade
     #pragma multi_compile _ LOD_FADE_CROSSFADE
 
-	// decal 3RT or 4RT toggle
-	#pragma multi_compile _ _DECALS_3RT _DECALS_4RT
-
     //enable GPU instancing support
     #pragma multi_compile_instancing
 
             #pragma multi_compile _ DIRLIGHTMAP_COMBINED
             #pragma multi_compile _ DYNAMICLIGHTMAP_ON
             #pragma multi_compile _ SHADOWS_SHADOWMASK
+            #pragma multi_compile _ DECALS_3RT DECALS_4RT
 
         #ifdef _ALPHATEST_ON
             // When we have alpha test, we will force a depth prepass so we always bypass the clip instruction in the GBuffer
             #pragma multi_compile _ DIRLIGHTMAP_COMBINED
             #pragma multi_compile _ DYNAMICLIGHTMAP_ON
             #pragma multi_compile _ SHADOWS_SHADOWMASK
+            #pragma multi_compile _ DECALS_3RT DECALS_4RT
+
             // #include "../../Lighting/Forward.hlsl"
             //#pragma multi_compile LIGHTLOOP_SINGLE_PASS LIGHTLOOP_TILE_PASS
             #define LIGHTLOOP_TILE_PASS

com.unity.render-pipelines.high-definition/HDRP/Material/LayeredLit/LayeredLitTessellation.shader

     // enable dithering LOD crossfade
     #pragma multi_compile _ LOD_FADE_CROSSFADE
 
-	// decal 3RT or 4RT toggle
-	#pragma multi_compile _ _DECALS_3RT _DECALS_4RT
-
     // enable GPU instancing
     #pragma multi_compile_instancing
 
             #pragma multi_compile _ DIRLIGHTMAP_COMBINED
             #pragma multi_compile _ DYNAMICLIGHTMAP_ON
             #pragma multi_compile _ SHADOWS_SHADOWMASK
+            #pragma multi_compile _ DECALS_3RT DECALS_4RT
 
         #ifdef _ALPHATEST_ON
             // When we have alpha test, we will force a depth prepass so we always bypass the clip instruction in the GBuffer
             #pragma multi_compile _ DIRLIGHTMAP_COMBINED
             #pragma multi_compile _ DYNAMICLIGHTMAP_ON
             #pragma multi_compile _ SHADOWS_SHADOWMASK
+            #pragma multi_compile _ DECALS_3RT DECALS_4RT
+
             // #include "../../Lighting/Forward.hlsl"
             //#pragma multi_compile LIGHTLOOP_SINGLE_PASS LIGHTLOOP_TILE_PASS
             #define LIGHTLOOP_TILE_PASS

com.unity.render-pipelines.high-definition/HDRP/Material/Lit/Lit.shader

     // enable dithering LOD crossfade
     #pragma multi_compile _ LOD_FADE_CROSSFADE
 
-	// decal 3RT or 4RT toggle
-	#pragma multi_compile _ _DECALS_3RT _DECALS_4RT
-
     //enable GPU instancing support
     #pragma multi_compile_instancing
 
             #pragma multi_compile _ DIRLIGHTMAP_COMBINED
             #pragma multi_compile _ DYNAMICLIGHTMAP_ON
             #pragma multi_compile _ SHADOWS_SHADOWMASK
+            #pragma multi_compile _ DECALS_3RT DECALS_4RT
 
         #ifdef _ALPHATEST_ON
             // When we have alpha test, we will force a depth prepass so we always bypass the clip instruction in the GBuffer
             #pragma multi_compile _ DIRLIGHTMAP_COMBINED
             #pragma multi_compile _ DYNAMICLIGHTMAP_ON
             #pragma multi_compile _ SHADOWS_SHADOWMASK
+            #pragma multi_compile _ DECALS_3RT DECALS_4RT
+
             // #include "../../Lighting/Forward.hlsl"
             //#pragma multi_compile LIGHTLOOP_SINGLE_PASS LIGHTLOOP_TILE_PASS
             #define LIGHTLOOP_TILE_PASS
             #pragma multi_compile _ DIRLIGHTMAP_COMBINED
             #pragma multi_compile _ DYNAMICLIGHTMAP_ON
             #pragma multi_compile _ SHADOWS_SHADOWMASK
+            #pragma multi_compile _ DECALS_3RT DECALS_4RT
+
             // #include "../../Lighting/Forward.hlsl"
             //#pragma multi_compile LIGHTLOOP_SINGLE_PASS LIGHTLOOP_TILE_PASS
             #define LIGHTLOOP_TILE_PASS

com.unity.render-pipelines.high-definition/HDRP/Material/Lit/LitTessellation.shader

     // enable dithering LOD crossfade
     #pragma multi_compile _ LOD_FADE_CROSSFADE
 
-	// decal 3RT or 4RT toggle
-	#pragma multi_compile _ _DECALS_3RT _DECALS_4RT
-
     //enable GPU instancing support
     #pragma multi_compile_instancing
 
             #pragma multi_compile _ DIRLIGHTMAP_COMBINED
             #pragma multi_compile _ DYNAMICLIGHTMAP_ON
             #pragma multi_compile _ SHADOWS_SHADOWMASK
+            #pragma multi_compile _ DECALS_3RT DECALS_4RT
 
         #ifdef _ALPHATEST_ON
             // When we have alpha test, we will force a depth prepass so we always bypass the clip instruction in the GBuffer
             #pragma multi_compile _ DIRLIGHTMAP_COMBINED
             #pragma multi_compile _ DYNAMICLIGHTMAP_ON
             #pragma multi_compile _ SHADOWS_SHADOWMASK
+            #pragma multi_compile _ DECALS_3RT DECALS_4RT
+
             // #include "../../Lighting/Forward.hlsl"
             //#pragma multi_compile LIGHTLOOP_SINGLE_PASS LIGHTLOOP_TILE_PASS
             #define LIGHTLOOP_TILE_PASS
             #pragma multi_compile _ DIRLIGHTMAP_COMBINED
             #pragma multi_compile _ DYNAMICLIGHTMAP_ON
             #pragma multi_compile _ SHADOWS_SHADOWMASK
+            #pragma multi_compile _ DECALS_3RT DECALS_4RT
+
             // #include "../../Lighting/Forward.hlsl"
             //#pragma multi_compile LIGHTLOOP_SINGLE_PASS LIGHTLOOP_TILE_PASS
             #define LIGHTLOOP_TILE_PASS

com.unity.render-pipelines.high-definition/HDRP/Material/Material.hlsl

 // - _ENABLE_FOG_ON_TRANSPARENT if fog is enable on transparent surface
 // - _DISABLE_DECALS if the material don't support decals
 
-#define HAVE_DECALS ( (defined(_DECALS_3RT) || defined(_DECALS_4RT)) && !defined(_DISABLE_DECALS) )
+#define HAVE_DECALS ( (defined(DECALS_3RT) || defined(DECALS_4RT)) && !defined(_DISABLE_DECALS) )
 
 //-----------------------------------------------------------------------------
 // ApplyBlendMode function

com.unity.render-pipelines.high-definition/HDRP/Material/StackLit/StackLit.shader

 
     #pragma shader_feature _STACKLIT_DEBUG
 
-	// decal 3RT or 4RT toggle
-	#pragma multi_compile _ _DECALS_3RT _DECALS_4RT
-
     //enable GPU instancing support
     #pragma multi_compile_instancing
 
             #pragma multi_compile _ DIRLIGHTMAP_COMBINED
             #pragma multi_compile _ DYNAMICLIGHTMAP_ON
             #pragma multi_compile _ SHADOWS_SHADOWMASK
+            #pragma multi_compile _ DECALS_3RT DECALS_4RT
 
             // #include "../../Lighting/Forward.hlsl" : nothing left in there.
             //#pragma multi_compile LIGHTLOOP_SINGLE_PASS LIGHTLOOP_TILE_PASS

com.unity.render-pipelines.high-definition/HDRP/RenderPipeline/HDRenderPipeline.cs

         {
             if (m_Asset.renderPipelineSettings.supportDecals)
             {
-                CoreUtils.SetKeyword(cmd, "_DECALS_3RT", !m_Asset.GetRenderPipelineSettings().decalSettings.perChannelMask);
-                CoreUtils.SetKeyword(cmd, "_DECALS_4RT", m_Asset.GetRenderPipelineSettings().decalSettings.perChannelMask);
+                CoreUtils.SetKeyword(cmd, "DECALS_3RT", !m_Asset.GetRenderPipelineSettings().decalSettings.perChannelMask);
+                CoreUtils.SetKeyword(cmd, "DECALS_4RT", m_Asset.GetRenderPipelineSettings().decalSettings.perChannelMask);
-                CoreUtils.SetKeyword(cmd, "_DECALS_3RT", false);
-                CoreUtils.SetKeyword(cmd, "_DECALS_4RT", false);
+                CoreUtils.SetKeyword(cmd, "DECALS_3RT", false);
+                CoreUtils.SetKeyword(cmd, "DECALS_4RT", false);
             }
         }