Merge pull request #2367 from KhronosGroup/spec-constant-switch

Handle SpecConstantOp used as switch case.

reference/shaders-no-opt/frag/switch-spec-constant-op.frag

@@ -0,0 +1,32 @@
+#version 450
+
+#ifndef SPIRV_CROSS_CONSTANT_ID_0
+#define SPIRV_CROSS_CONSTANT_ID_0 4
+#endif
+const int FOO = SPIRV_CROSS_CONSTANT_ID_0;
+const int _9 = (FOO + 4);
+
+layout(location = 0) out vec4 FragColor;
+
+void main()
+{
+    switch (_9)
+    {
+        case 4:
+        {
+            FragColor = vec4(10.0);
+            break;
+        }
+        case 6:
+        {
+            FragColor = vec4(20.0);
+            break;
+        }
+        default:
+        {
+            FragColor = vec4(0.0);
+            break;
+        }
+    }
+}
+

shaders-no-opt/frag/switch-spec-constant-op.frag

@@ -0,0 +1,23 @@
+#version 450
+
+layout(location = 0) out vec4 FragColor;
+layout(location = 0) in vec4 Attr;
+layout(constant_id = 0) const int FOO = 4;
+
+void main()
+{
+	switch (FOO + 4)
+	{
+		case 4:
+			FragColor = vec4(10.0);
+			break;
+
+		case 6:
+			FragColor = vec4(20.0);
+			break;
+
+		default:
+			FragColor = vec4(0.0);
+			break;
+	}
+}

spirv_cross.cpp

@@ -1850,6 +1850,11 @@ const SmallVector<SPIRBlock::Case> &Compiler::get_case_list(const SPIRBlock &blo
 		const auto &type = get<SPIRType>(constant->constant_type);
 		width = type.width;
 	}
+	else if (const auto *op = maybe_get<SPIRConstantOp>(block.condition))
+	{
+		const auto &type = get<SPIRType>(op->basetype);
+		width = type.width;
+	}
 	else if (const auto *var = maybe_get<SPIRVariable>(block.condition))
 	{
 		const auto &type = get<SPIRType>(var->basetype);