From 86dfac12c887ae8622f7370b4f9958250d8f2965 Mon Sep 17 00:00:00 2001
From: Bill Hollings <bill.hollings@brenwill.com>
Date: Sat, 18 Sep 2021 18:55:12 -0400
Subject: [PATCH] MSL: Fix location and component variable matching between
 shader stages.

Consolidate derivation of Metal 'user(locnL_C)' output/input location
and component attribute qualifier, to establish SVOT across stages.
---
 spirv_msl.cpp | 55 ++++++++++++++++++++++++++-------------------------
 spirv_msl.hpp |  1 +
 2 files changed, 29 insertions(+), 27 deletions(-)

diff --git a/spirv_msl.cpp b/spirv_msl.cpp
index acd71ace..28b5c2d6 100644
--- a/spirv_msl.cpp
+++ b/spirv_msl.cpp
@@ -10666,15 +10666,9 @@ string CompilerMSL::member_attribute_qualifier(const SPIRType &type, uint32_t in
 				return "";
 			}
 		}
-		uint32_t comp;
-		uint32_t locn = get_member_location(type.self, index, &comp);
-		if (locn != k_unknown_location)
-		{
-			if (comp != k_unknown_component)
-				return string(" [[user(locn") + convert_to_string(locn) + "_" + convert_to_string(comp) + ")]]";
-			else
-				return string(" [[user(locn") + convert_to_string(locn) + ")]]";
-		}
+		string loc_qual = member_location_attribute_qualifier(type, index);
+		if (!loc_qual.empty())
+			return join(" [[", loc_qual, "]]");
 	}
 
 	// Tessellation control function inputs
@@ -10788,24 +10782,7 @@ string CompilerMSL::member_attribute_qualifier(const SPIRType &type, uint32_t in
 			}
 		}
 		else
-		{
-			uint32_t comp;
-			uint32_t locn = get_member_location(type.self, index, &comp);
-			if (locn != k_unknown_location)
-			{
-				// For user-defined attributes, this is fine. From Vulkan spec:
-				// A user-defined output variable is considered to match an input variable in the subsequent stage if
-				// the two variables are declared with the same Location and Component decoration and match in type
-				// and decoration, except that interpolation decorations are not required to match. For the purposes
-				// of interface matching, variables declared without a Component decoration are considered to have a
-				// Component decoration of zero.
-
-				if (comp != k_unknown_component && comp != 0)
-					quals = string("user(locn") + convert_to_string(locn) + "_" + convert_to_string(comp) + ")";
-				else
-					quals = string("user(locn") + convert_to_string(locn) + ")";
-			}
-		}
+			quals = member_location_attribute_qualifier(type, index);
 
 		if (builtin == BuiltInBaryCoordNV || builtin == BuiltInBaryCoordNoPerspNV)
 		{
@@ -10937,6 +10914,30 @@ string CompilerMSL::member_attribute_qualifier(const SPIRType &type, uint32_t in
 	return "";
 }
 
+// A user-defined output variable is considered to match an input variable in the subsequent
+// stage if the two variables are declared with the same Location and Component decoration and
+// match in type and decoration, except that interpolation decorations are not required to match.
+// For the purposes of interface matching, variables declared without a Component decoration are
+// considered to have a Component decoration of zero.
+string CompilerMSL::member_location_attribute_qualifier(const SPIRType &type, uint32_t index)
+{
+	string quals;
+	uint32_t comp;
+	uint32_t locn = get_member_location(type.self, index, &comp);
+	if (locn != k_unknown_location)
+	{
+		quals += "user(locn";
+		quals += convert_to_string(locn);
+		if (comp != k_unknown_component && comp != 0)
+		{
+			quals += "_";
+			quals += convert_to_string(comp);
+		}
+		quals += ")";
+	}
+	return quals;
+}
+
 // Returns the location decoration of the member with the specified index in the specified type.
 // If the location of the member has been explicitly set, that location is used. If not, this
 // function assumes the members are ordered in their location order, and simply returns the
diff --git a/spirv_msl.hpp b/spirv_msl.hpp
index a34ae32e..9dc1a1a0 100644
--- a/spirv_msl.hpp
+++ b/spirv_msl.hpp
@@ -867,6 +867,7 @@ protected:
 	std::string builtin_type_decl(spv::BuiltIn builtin, uint32_t id = 0);
 	std::string built_in_func_arg(spv::BuiltIn builtin, bool prefix_comma);
 	std::string member_attribute_qualifier(const SPIRType &type, uint32_t index);
+	std::string member_location_attribute_qualifier(const SPIRType &type, uint32_t index);
 	std::string argument_decl(const SPIRFunction::Parameter &arg);
 	std::string round_fp_tex_coords(std::string tex_coords, bool coord_is_fp);
 	uint32_t get_metal_resource_index(SPIRVariable &var, SPIRType::BaseType basetype, uint32_t plane = 0);