FunctionSignatureTransforms: add a semantics attribute to prevent the owned-to-guarantee transformation.

If a function is annotated with @_semantics("optimize.sil.specialize.owned2guarantee.never") its arguments will not be converted from owned to guaranteed.

Author: eeckstein

include/swift/AST/SemanticAttrs.def

@@ -67,6 +67,8 @@ SEMANTICS_ATTR(OPTIMIZE_SIL_SPECIALIZE_GENERIC_PARTIAL_NEVER,
           "optimize.sil.specialize.generic.partial.never")
 SEMANTICS_ATTR(OPTIMIZE_SIL_SPECIALIZE_GENERIC_SIZE_NEVER,
           "optimize.sil.specialize.generic.size.never")
+SEMANTICS_ATTR(OPTIMIZE_SIL_SPECIALIZE_OWNED2GUARANTEE_NEVER,
+          "optimize.sil.specialize.owned2guarantee.never")
 
 SEMANTICS_ATTR(OSLOG_MESSAGE_INIT_INTERPOLATION, "oslog.message.init_interpolation")
 SEMANTICS_ATTR(OSLOG_MESSAGE_INIT_STRING_LITERAL, "oslog.message.init_stringliteral")

lib/SILOptimizer/FunctionSignatureTransforms/OwnedToGuaranteedTransform.cpp

@@ -13,6 +13,7 @@
 #define DEBUG_TYPE "fso-owned-to-guaranteed-transform"
 #include "FunctionSignatureOpts.h"
 #include "swift/SIL/DebugUtils.h"
+#include "swift/AST/SemanticAttrs.h"
 #include "llvm/Support/CommandLine.h"
 
 using namespace swift;
@@ -258,6 +259,9 @@ void FunctionSignatureTransform::OwnedToGuaranteedAddResultRelease(
 bool FunctionSignatureTransform::OwnedToGuaranteedAnalyze() {
   if (FSODisableOwnedToGuaranteed)
     return false;
+  SILFunction *F = TransformDescriptor.OriginalFunction;
+  if (F->hasSemanticsAttr(semantics::OPTIMIZE_SIL_SPECIALIZE_OWNED2GUARANTEE_NEVER))
+    return false;
 
   const bool Result = OwnedToGuaranteedAnalyzeResults();
   const bool Params = OwnedToGuaranteedAnalyzeParameters();