Add support for GL_EXT_texture_shadow_lod.

reference/shaders/asm/frag/texture-shadow-lod.asm.frag

@@ -0,0 +1,14 @@
+#version 450
+#extension GL_EXT_texture_shadow_lod : require
+
+layout(binding = 0) uniform sampler2DArrayShadow uShadow2DArray;
+
+layout(location = 0) out vec4 FragColor;
+layout(location = 0) in vec4 vUV;
+layout(location = 1) in float vLod;
+
+void main()
+{
+    FragColor = vec4(textureLod(uShadow2DArray, vec4(vUV.xyz, vUV.w), vLod));
+}
+

reference/shaders/frag/texture-shadow-lod-bias.frag

@@ -0,0 +1,17 @@
+#version 450
+#extension GL_EXT_texture_shadow_lod : require
+
+layout(binding = 0) uniform sampler2DArrayShadow uShadow2DArray;
+
+layout(location = 0) in vec4 vUV;
+layout(location = 1) in float vBias;
+layout(location = 0) out vec4 FragColor;
+
+void main()
+{
+    float r = 0.0;
+    r += texture(uShadow2DArray, vec4(vUV.xyz, vUV.w), vBias);
+    r += textureOffset(uShadow2DArray, vec4(vUV.xyz, vUV.w), ivec2(1), vBias);
+    FragColor = vec4(r);
+}
+

reference/shaders/frag/texture-shadow-lod.frag

@@ -0,0 +1,19 @@
+#version 450
+#extension GL_EXT_texture_shadow_lod : require
+
+layout(binding = 0) uniform sampler2DArrayShadow uShadow2DArray;
+layout(binding = 1) uniform samplerCubeShadow uShadowCube;
+
+layout(location = 0) in vec4 vUV;
+layout(location = 1) in float vLod;
+layout(location = 0) out vec4 FragColor;
+
+void main()
+{
+    float r = 0.0;
+    r += textureLod(uShadow2DArray, vec4(vUV.xyz, vUV.w), vLod);
+    r += textureLod(uShadowCube, vec4(vUV.xyz, vUV.w), vLod);
+    r += textureLodOffset(uShadow2DArray, vec4(vUV.xyz, vUV.w), vLod, ivec2(1));
+    FragColor = vec4(r);
+}
+

shaders/asm/frag/texture-shadow-lod.asm.frag

@@ -0,0 +1,45 @@
+; SPIR-V
+; Version: 1.0
+; Generator: Khronos Glslang Reference Front End; 1
+; Bound: 50
+; Schema: 0
+               OpCapability Shader
+          %1 = OpExtInstImport "GLSL.std.450"
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint Fragment %main "main" %FragColor %vUV %vLod
+               OpExecutionMode %main OriginUpperLeft
+               OpName %main "main"
+               OpName %FragColor "FragColor"
+               OpName %uShadow2DArray "uShadow2DArray"
+               OpName %vUV "vUV"
+               OpName %vLod "vLod"
+               OpDecorate %FragColor Location 0
+               OpDecorate %uShadow2DArray DescriptorSet 0
+               OpDecorate %uShadow2DArray Binding 0
+               OpDecorate %vUV Location 0
+               OpDecorate %vLod Location 1
+       %void = OpTypeVoid
+          %3 = OpTypeFunction %void
+      %float = OpTypeFloat 32
+    %v4float = OpTypeVector %float 4
+%_ptr_Output_v4float = OpTypePointer Output %v4float
+  %FragColor = OpVariable %_ptr_Output_v4float Output
+         %10 = OpTypeImage %float 2D 1 1 0 1 Unknown
+         %11 = OpTypeSampledImage %10
+%_ptr_UniformConstant_11 = OpTypePointer UniformConstant %11
+%uShadow2DArray = OpVariable %_ptr_UniformConstant_11 UniformConstant
+%_ptr_Input_v4float = OpTypePointer Input %v4float
+        %vUV = OpVariable %_ptr_Input_v4float Input
+%_ptr_Input_float = OpTypePointer Input %float
+       %vLod = OpVariable %_ptr_Input_float Input
+       %main = OpFunction %void None %3
+          %5 = OpLabel
+         %14 = OpLoad %11 %uShadow2DArray
+         %17 = OpLoad %v4float %vUV
+         %19 = OpLoad %float %vLod
+         %20 = OpCompositeExtract %float %17 3
+         %21 = OpImageSampleDrefExplicitLod %float %14 %17 %20 Lod %19
+         %22 = OpCompositeConstruct %v4float %21 %21 %21 %21
+               OpStore %FragColor %22
+               OpReturn
+               OpFunctionEnd

shaders/frag/texture-shadow-lod-bias.frag

@@ -0,0 +1,16 @@
+#version 450
+#extension GL_EXT_texture_shadow_lod : require
+
+layout(binding = 0) uniform sampler2DArrayShadow uShadow2DArray;
+
+layout(location = 0) in vec4 vUV;
+layout(location = 1) in float vBias;
+layout(location = 0) out vec4 FragColor;
+
+void main()
+{
+    float r = 0.0;
+    r += texture(uShadow2DArray, vUV, vBias);
+    r += textureOffset(uShadow2DArray, vUV, ivec2(1, 1), vBias);
+    FragColor = vec4(r);
+}

shaders/frag/texture-shadow-lod.frag

@@ -0,0 +1,18 @@
+#version 450
+#extension GL_EXT_texture_shadow_lod : require
+
+layout(binding = 0) uniform sampler2DArrayShadow uShadow2DArray;
+layout(binding = 1) uniform samplerCubeShadow uShadowCube;
+
+layout(location = 0) in vec4 vUV;
+layout(location = 1) in float vLod;
+layout(location = 0) out vec4 FragColor;
+
+void main()
+{
+    float r = 0.0;
+    r += textureLod(uShadow2DArray, vUV, vLod);
+    r += textureLod(uShadowCube, vUV, vLod);
+    r += textureLodOffset(uShadow2DArray, vUV, vLod, ivec2(1, 1));
+    FragColor = vec4(r);
+}

spirv_glsl.cpp

@@ -8236,6 +8236,17 @@ std::string CompilerGLSL::to_texture_op(const Instruction &i, bool sparse, bool
 	base_args.is_proj = proj != 0;
 
 	string expr;
+
+	// texture() with bias on sampler2DArrayShadow or samplerCubeArrayShadow requires GL_EXT_texture_shadow_lod.
+	// textureOffset() with bias on sampler2DArrayShadow also requires it.
+	if (bias != 0 && dref != 0 && !fetch && !gather &&
+	    ((imgtype.image.arrayed && imgtype.image.dim == Dim2D) ||
+	     (imgtype.image.arrayed && imgtype.image.dim == DimCube)) &&
+	    is_depth_image(imgtype, img))
+	{
+		require_extension_internal("GL_EXT_texture_shadow_lod");
+	}
+
 	TextureFunctionNameArguments name_args = {};
 
 	name_args.base = base_args;
@@ -8372,10 +8383,12 @@ string CompilerGLSL::to_function_name(const TextureFunctionNameArguments &args)
 	{
 		if (!expression_is_constant_null(args.lod))
 		{
-			SPIRV_CROSS_THROW("textureLod on sampler2DArrayShadow is not constant 0.0. This cannot be "
-			                  "expressed in GLSL.");
+			require_extension_internal("GL_EXT_texture_shadow_lod");
+		}
+		else
+		{
+			workaround_lod_array_shadow_as_grad = true;
 		}
-		workaround_lod_array_shadow_as_grad = true;
 	}
 
 	if (args.is_sparse_feedback)
@@ -8510,9 +8523,11 @@ string CompilerGLSL::to_function_args(const TextureFunctionArguments &args, bool
 	// To emulate this, we will have to use textureGrad with a constant gradient of 0.
 	// The workaround will assert that the LOD is in fact constant 0, or we cannot emit correct code.
 	// This happens for HLSL SampleCmpLevelZero on Texture2DArray and TextureCube.
+	// If GL_EXT_texture_shadow_lod is in use, textureLod is available directly with arbitrary LOD.
 	bool workaround_lod_array_shadow_as_grad =
 	    ((imgtype.image.arrayed && imgtype.image.dim == Dim2D) || imgtype.image.dim == DimCube) &&
-	    is_depth_image(imgtype, img) && args.lod != 0 && !args.base.is_fetch;
+	    is_depth_image(imgtype, img) && args.lod != 0 && !args.base.is_fetch &&
+	    !has_extension("GL_EXT_texture_shadow_lod");
 
 	if (args.dref)
 	{