Add support for SPV_KHR_multiview.

reference/shaders/vulkan/vert/multiview.nocompat.vk.vert

@@ -0,0 +1,15 @@
+#version 310 es
+#extension GL_OVR_multiview2 : require
+
+layout(binding = 0, std140) uniform MVPs
+{
+    mat4 MVP[2];
+} _19;
+
+layout(location = 0) in vec4 Position;
+
+void main()
+{
+    gl_Position = _19.MVP[gl_ViewID_OVR] * Position;
+}
+

reference/shaders/vulkan/vert/multiview.nocompat.vk.vert.vk

@@ -0,0 +1,15 @@
+#version 310 es
+#extension GL_EXT_multiview : require
+
+layout(set = 0, binding = 0, std140) uniform MVPs
+{
+    mat4 MVP[2];
+} _19;
+
+layout(location = 0) in vec4 Position;
+
+void main()
+{
+    gl_Position = _19.MVP[gl_ViewIndex] * Position;
+}
+

shaders/vulkan/vert/multiview.nocompat.vk.vert

@@ -0,0 +1,14 @@
+#version 310 es
+#extension GL_EXT_multiview : require
+
+layout(std140, binding = 0) uniform MVPs
+{
+	mat4 MVP[2];
+};
+
+layout(location = 0) in vec4 Position;
+
+void main()
+{
+	gl_Position = MVP[gl_ViewIndex] * Position;
+}

spirv_glsl.cpp

@@ -3619,6 +3619,18 @@ string CompilerGLSL::builtin_to_glsl(BuiltIn builtin, StorageClass storage)
 			SPIRV_CROSS_THROW("gl_SamplePosition not supported before GLSL 400.");
 		return "gl_SamplePosition";
 
+	case BuiltInViewIndex:
+		if (options.vulkan_semantics)
+		{
+			require_extension("GL_EXT_multiview");
+			return "gl_ViewIndex";
+		}
+		else
+		{
+			require_extension("GL_OVR_multiview2");
+			return "gl_ViewID_OVR";
+		}
+
 	default:
 		return join("gl_BuiltIn_", convert_to_string(builtin));
 	}