wgsl: Fix field semantics even if input struct doesn't need flattening (#5642)

* wgsl: Fix field semantics even if input struct doesn't need flattening

Helps to address issue #5633.

* Add test for multiple stage IO locations

This verifies part of issue #5633.

1 files changed, 2 insertions, 3 deletions

diff --git a/source/slang/slang-ir-wgsl-legalize.cpp b/source/slang/slang-ir-wgsl-legalize.cpp
index 4d617a169..8eb820b4d 100644
--- a/source/slang/slang-ir-wgsl-legalize.cpp
+++ b/source/slang/slang-ir-wgsl-legalize.cpp
@@ -145,11 +145,10 @@ struct LegalizeWGSLEntryPointContext
                     structType,
                     mapOldFieldToNewField,
                     semanticInfoToRemove);
+                // Validate/rearange all semantics which overlap in our flat struct.
+                fixFieldSemanticsOfFlatStruct(flattenedStruct);
                 if (flattenedStruct != structType)
                 {
-                    // Validate/rearange all semantics which overlap in our flat struct
-                    fixFieldSemanticsOfFlatStruct(flattenedStruct);
-
                     // Replace the 'old IRParam type' with a 'new IRParam type'
                     param->setFullType(flattenedStruct);