Metal remove void field (#6725)

* Reapply "Eliminate empty struct on metal target (#6603)" (#6711)

This reverts commit bc9dc6557fc0cc3a4c0c2ff27e636940e361cf5d.

* Remove argument in make_struct call corresponding to void field

This is a follow-up of #6543, where we leave the VoidType field as it in
make_struct call during legalization pass.

So during cleaning_void IR pass, when we remove "VoidType" from struct,
we will have to also clean up the argument corresponding to the
"VoidType" field.

1 files changed, 5 insertions, 1 deletions

diff --git a/source/slang/slang-legalize-types.cpp b/source/slang/slang-legalize-types.cpp
index e26475522..cc2c12d42 100644
--- a/source/slang/slang-legalize-types.cpp
+++ b/source/slang/slang-legalize-types.cpp
@@ -1211,11 +1211,15 @@ LegalType legalizeTypeImpl(TypeLegalizationContext* context, IRType* type)
         LegalType legalElementType;
 
         if (isMetalTarget(context->targetProgram->getTargetReq()) &&
-            as<IRParameterBlockType>(uniformBufferType))
+            as<IRParameterBlockType>(uniformBufferType) &&
+            !context->shouldLegalizeParameterBlockElementType())
         {
             // On Metal, we do not need to legalize the element type of
             // a parameter block because we can translate it directly into
             // an argument buffer.
+            //
+            // But we do need empty type legalized for Metal, because Metal doesn't
+            // allow empty struct in argument buffer.
             legalElementType = LegalType::simple(originalElementType);
         }
         else