Screenspace shadow resolve is only done in case of cascade shadows.

com.unity.render-pipelines.lightweight/LWRP/Editor/ShaderGraph/lightweightPBRForwardPass.template

     #pragma multi_compile _ _SHADOWS_ENABLED
     #pragma multi_compile _ _LOCAL_SHADOWS_ENABLED
     #pragma multi_compile _ _SHADOWS_SOFT
+    #pragma multi_compile _ _SHADOWS_CASCADES
 
 	// -------------------------------------
     // Unity defined keywords
     }
 
 	ENDHLSL
-}
+}

com.unity.render-pipelines.lightweight/LWRP/Editor/ShaderPreprocessor.cs

         public static readonly ShaderKeyword DirectionalShadows = new ShaderKeyword(LightweightKeywordStrings.DirectionalShadows);
         public static readonly ShaderKeyword LocalShadows = new ShaderKeyword(LightweightKeywordStrings.LocalShadows);
         public static readonly ShaderKeyword SoftShadows = new ShaderKeyword(LightweightKeywordStrings.SoftShadows);
+        public static readonly ShaderKeyword CascadeShadows = new ShaderKeyword(LightweightKeywordStrings.CascadeShadows);
 
         public static readonly ShaderKeyword Lightmap = new ShaderKeyword("LIGHTMAP_ON");
         public static readonly ShaderKeyword DirectionalLightmap = new ShaderKeyword("DIRLIGHTMAP_COMBINED");
 
         bool StripInvalidVariants(ShaderCompilerData compilerData)
         {
-            bool isShadowVariant = compilerData.shaderKeywordSet.IsEnabled(LightweightKeyword.DirectionalShadows) ||
-                compilerData.shaderKeywordSet.IsEnabled(LightweightKeyword.LocalShadows);
+            bool isDirectionalShadows = compilerData.shaderKeywordSet.IsEnabled(LightweightKeyword.DirectionalShadows);
+            bool isShadowVariant = isDirectionalShadows || compilerData.shaderKeywordSet.IsEnabled(LightweightKeyword.LocalShadows);
+
+            if (!isDirectionalShadows && compilerData.shaderKeywordSet.IsEnabled(LightweightKeyword.CascadeShadows))
+                return true;
-            if (compilerData.shaderKeywordSet.IsEnabled(LightweightKeyword.SoftShadows) && !isShadowVariant)
+            if (!isShadowVariant && compilerData.shaderKeywordSet.IsEnabled(LightweightKeyword.SoftShadows))
                 return true;
 
             if (compilerData.shaderKeywordSet.IsEnabled(LightweightKeyword.VertexLights) &&

com.unity.render-pipelines.lightweight/LWRP/LightweightPipeline.cs

             bool supportsScreenSpaceShadows = SystemInfo.graphicsDeviceType != GraphicsDeviceType.OpenGLES2;
 
             shadowData.renderDirectionalShadows = pipelineAsset.supportsDirectionalShadows && hasDirectionalShadowCastingLight;
-            shadowData.requiresScreenSpaceShadowResolve = shadowData.renderDirectionalShadows && supportsScreenSpaceShadows;
+
+            // we resolve shadows in screenspace when cascades are enabled to save ALU as computing cascade index + shadowCoord on fragment is expensive
+            shadowData.requiresScreenSpaceShadowResolve = shadowData.renderDirectionalShadows && supportsScreenSpaceShadows && pipelineAsset.cascadeCount > 1;
             shadowData.directionalLightCascadeCount = (shadowData.requiresScreenSpaceShadowResolve) ? pipelineAsset.cascadeCount : 1;
             shadowData.directionalShadowAtlasWidth = pipelineAsset.directionalShadowAtlasResolution;
             shadowData.directionalShadowAtlasHeight = pipelineAsset.directionalShadowAtlasResolution;

com.unity.render-pipelines.lightweight/LWRP/Passes/DirectionalShadowsPass.cs

                 if (success)
                 {
                     shadowQuality = (shadowData.supportsSoftShadows) ? light.shadows : LightShadows.Hard;
-
-                    // In order to avoid shader variants explosion we only do hard shadows when sampling shadowmap in the lit pass.
-                    // GLES2 platform is forced to hard single cascade shadows.
-                    if (!shadowData.requiresScreenSpaceShadowResolve)
-                        shadowQuality = LightShadows.Hard;
-
                     SetupDirectionalShadowReceiverConstants(ref context, cmd, ref shadowData, shadowLight);
                 }
             }

com.unity.render-pipelines.lightweight/LWRP/Passes/ForwardLitPass.cs

             CoreUtils.SetKeyword(cmd, LightweightKeywordStrings.DirectionalShadows, directionalShadowQuality != LightShadows.None);
             CoreUtils.SetKeyword(cmd, LightweightKeywordStrings.LocalShadows, localShadowQuality != LightShadows.None);
             CoreUtils.SetKeyword(cmd, LightweightKeywordStrings.SoftShadows, hasSoftShadows);
+            CoreUtils.SetKeyword(cmd, LightweightKeywordStrings.CascadeShadows, shadowData.directionalLightCascadeCount > 1);
 
             // TODO: Remove this. legacy particles support will be removed from Unity in 2018.3. This should be a shader_feature instead with prop exposed in the Standard particles shader.
             CoreUtils.SetKeyword(cmd, "SOFTPARTICLES_ON", cameraData.requiresSoftParticles);

com.unity.render-pipelines.lightweight/LWRP/Passes/ScreenSpaceShadowResolvePass.cs

         void SetShadowCollectPassKeywords(CommandBuffer cmd, ref ShadowData shadowData)
         {
             CoreUtils.SetKeyword(cmd, LightweightKeywordStrings.SoftShadows, shadowData.renderedDirectionalShadowQuality == LightShadows.Soft);
-            CoreUtils.SetKeyword(cmd, LightweightKeywordStrings.CascadeShadows, shadowData.directionalLightCascadeCount > 1);
         }
     }
 }

com.unity.render-pipelines.lightweight/LWRP/ShaderLibrary/Shadows.hlsl

 #define MAX_SHADOW_CASCADES 4
 
 #ifndef SHADOWS_SCREEN
-#ifdef SHADER_API_GLES
+#if defined(SHADER_API_GLES) || !defined(_SHADOWS_CASCADE)
 #define SHADOWS_SCREEN 0
 #else
 #define SHADOWS_SCREEN 1

com.unity.render-pipelines.lightweight/LWRP/Shaders/LightweightScreenSpaceShadows.shader

         #include "LWRP/ShaderLibrary/Core.hlsl"
         #include "LWRP/ShaderLibrary/Shadows.hlsl"
 
+        // Note: Screenspace shadow resolve is only performed when shadow cascades are enabled
+        // Shadow cascades require cascade index and shadowCoord to be computed on pixel.
+        #define _SHADOWS_CASCADE
+
 #if defined(UNITY_STEREO_INSTANCING_ENABLED) || defined(UNITY_STEREO_MULTIVIEW_ENABLED)
         TEXTURE2D_ARRAY_FLOAT(_CameraDepthTexture);
 #else
 
             HLSLPROGRAM
             #pragma multi_compile _ _SHADOWS_SOFT
-            #pragma multi_compile _ _SHADOWS_CASCADE
 
             #pragma vertex   Vertex
             #pragma fragment Fragment

com.unity.render-pipelines.lightweight/LWRP/Shaders/LightweightStandard.shader

             #pragma multi_compile _ _SHADOWS_ENABLED
             #pragma multi_compile _ _LOCAL_SHADOWS_ENABLED
             #pragma multi_compile _ _SHADOWS_SOFT
+            #pragma multi_compile _ _SHADOWS_CASCADES
 
             // -------------------------------------
             // Unity defined keywords

com.unity.render-pipelines.lightweight/LWRP/Shaders/LightweightStandardSimpleLighting.shader

             #pragma multi_compile _ _SHADOWS_ENABLED
             #pragma multi_compile _ _LOCAL_SHADOWS_ENABLED
             #pragma multi_compile _ _SHADOWS_SOFT
+            #pragma multi_compile _ _SHADOWS_CASCADE
 
             // -------------------------------------
             // Unity defined keywords

com.unity.render-pipelines.lightweight/LWRP/Shaders/Terrain/LightweightStandardTerrain.shader

             #pragma multi_compile _ _SHADOWS_ENABLED
             #pragma multi_compile _ _LOCAL_SHADOWS_ENABLED
             #pragma multi_compile _ _SHADOWS_SOFT
+            #pragma multi_compile _ _SHADOWS_CASCADE
 
             // -------------------------------------
             // Unity defined keywords

com.unity.render-pipelines.lightweight/LWRP/Shaders/Terrain/LightweightStandardTerrainAddPass.shader

             #pragma multi_compile _ _SHADOWS_ENABLED
             #pragma multi_compile _ _LOCAL_SHADOWS_ENABLED
             #pragma multi_compile _ _SHADOWS_SOFT
+            #pragma multi_compile _ _SHADOWS_CASCADE
 
             // -------------------------------------
             // Unity defined keywords

com.unity.render-pipelines.lightweight/LWRP/Shaders/Terrain/LightweightStandardTerrainBase.shader

             #pragma multi_compile _ _SHADOWS_ENABLED
             #pragma multi_compile _ _LOCAL_SHADOWS_ENABLED
             #pragma multi_compile _ _SHADOWS_SOFT
+            #pragma multi_compile _ _SHADOWS_CASCADE
 
             // -------------------------------------
             // Unity defined keywords

com.unity.render-pipelines.lightweight/LWRP/Shaders/Terrain/LightweightWavingGrass.shader

             #pragma multi_compile _ _SHADOWS_ENABLED
             #pragma multi_compile _ _LOCAL_SHADOWS_ENABLED
             #pragma multi_compile _ _SHADOWS_SOFT
+            #pragma multi_compile _ _SHADOWS_CASCADE
 
             // -------------------------------------
             // Unity defined keywords

com.unity.render-pipelines.lightweight/LWRP/Shaders/Terrain/LightweightWavingGrassBillboard.shader

             #pragma multi_compile _ _SHADOWS_ENABLED
             #pragma multi_compile _ _LOCAL_SHADOWS_ENABLED
             #pragma multi_compile _ _SHADOWS_SOFT
+            #pragma multi_compile _ _SHADOWS_CASCADE
 
             // -------------------------------------
             // Unity defined keywords