[sil-inliner] Respect the @inline(__always) and @_transparent even if inlining of generics is disabled

If some functions are explicitly annotated by developers as @inline(__always) or @_transparent, they should always be a subject for the inlining of generics, even if this kind of inlining is not enabled currently for all functions.

Author: swiftix

lib/SILOptimizer/Transforms/PerformanceInliner.cpp

@@ -365,15 +365,6 @@ static Optional<bool> shouldInlineGeneric(FullApplySite AI) {
   assert(!AI.getSubstitutions().empty() &&
          "Expected a generic apply");
 
-  if (!EnableSILInliningOfGenerics)
-    return false;
-
-  // If all substitutions are concrete, then there is no need to perform the
-  // generic inlining. Let the generic specializer create a specialized
-  // function and then decide if it is beneficial to inline it.
-  if (!hasArchetypes(AI.getSubstitutions()))
-    return false;
-
   SILFunction *Callee = AI.getReferencedFunction();
 
   // Do not inline @_semantics functions when compiling the stdlib,
@@ -393,6 +384,17 @@ static Optional<bool> shouldInlineGeneric(FullApplySite AI) {
   if (Callee->getInlineStrategy() == AlwaysInline || Callee->isTransparent())
     return true;
 
+  // All other generic functions should not be inlined if this kind of inlining
+  // is disabled.
+  if (!EnableSILInliningOfGenerics)
+    return false;
+
+  // If all substitutions are concrete, then there is no need to perform the
+  // generic inlining. Let the generic specializer create a specialized
+  // function and then decide if it is beneficial to inline it.
+  if (!hasArchetypes(AI.getSubstitutions()))
+    return false;
+
   // It is not clear yet if this function should be decided or not.
   return None;
 }

lib/SILOptimizer/Utils/PerformanceInlinerUtils.cpp

@@ -678,8 +678,10 @@ SILFunction *swift::getEligibleFunction(FullApplySite AI,
   }
 
   if (!EnableSILInliningOfGenerics && AI.hasSubstitutions()) {
-    // Inlining of generics is not allowed.
-    return nullptr;
+    // Inlining of generics is not allowed unless it is an @inline(__always)
+    // or transparent function.
+    if (Callee->getInlineStrategy() != AlwaysInline && !Callee->isTransparent())
+      return nullptr;
   }
 
   // IRGen cannot handle partial_applies containing opened_existentials