Transfer offset decorations when legalizing laid-out structs (#5525)

* Transfer offset decorations when legalizing laid-out structs

Struct legalization removing fields not representable in memory should transfer all
decorations in case the struct has already had offsets calculated.

Closes #5264.

* format code

---------

Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>
Co-authored-by: Yong He <yonghe@outlook.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/source/slang/slang-legalize-types.cpp b/source/slang/slang-legalize-types.cpp
index 9c79e3167..6d827a412 100644
--- a/source/slang/slang-legalize-types.cpp
+++ b/source/slang/slang-legalize-types.cpp
@@ -487,8 +487,13 @@ struct TupleTypeBuilder
                     fieldType = context->getBuilder()->getVoidType();
 
                 // TODO: shallow clone of modifiers, etc.
-
-                builder->createStructField(ordinaryStructType, ee.fieldKey, fieldType);
+                IRStructField* originalField = findStructField(originalStructType, ee.fieldKey);
+                IRStructField* newField =
+                    builder->createStructField(ordinaryStructType, ee.fieldKey, fieldType);
+                // In case the original struct had offset decorations attached, transfer those as
+                // well. The original offsets should still be valid, since we only skip fields of
+                // types that aren't representable in memory.
+                originalField->transferDecorationsTo(newField);
             }
 
             ordinaryType = LegalType::simple((IRType*)ordinaryStructType);