Inliner: Add @_semantics("inline_late")

@_semantics(inline_late) for inlining only outside the standard library in the
late performance inliner.

It can be beneficial to run the inliner only outside the standard library when
code size has been reduced far enough that inlining can take place based on the
inliner's heuristics.

rdar://33099675
SR-5360

Author: aschwaighofer

lib/SILOptimizer/Utils/PerformanceInlinerUtils.cpp

@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "swift/SILOptimizer/Utils/PerformanceInlinerUtils.h"
+#include "swift/Strings.h"
 
 //===----------------------------------------------------------------------===//
 //                               ConstantTracker
@@ -630,20 +631,32 @@ SILFunction *swift::getEligibleFunction(FullApplySite AI,
   if (!Callee) {
     return nullptr;
   }
+  auto ModuleName = Callee->getModule().getSwiftModule()->getName().str();
+  bool IsInStdlib = (ModuleName == STDLIB_NAME || ModuleName == SWIFT_ONONE_SUPPORT);
 
   // Don't inline functions that are marked with the @_semantics or @effects
   // attribute if the inliner is asked not to inline them.
   if (Callee->hasSemanticsAttrs() || Callee->hasEffectsKind()) {
     if (WhatToInline == InlineSelection::NoSemanticsAndGlobalInit) {
       if (shouldSkipApplyDuringEarlyInlining(AI))
         return nullptr;
+      if (Callee->hasSemanticsAttr("inline_late"))
+        return nullptr;
     }
     // The "availability" semantics attribute is treated like global-init.
     if (Callee->hasSemanticsAttrs() &&
         WhatToInline != InlineSelection::Everything &&
-        Callee->hasSemanticsAttrThatStartsWith("availability")) {
+        (Callee->hasSemanticsAttrThatStartsWith("availability") ||
+         (Callee->hasSemanticsAttrThatStartsWith("inline_late")))) {
       return nullptr;
     }
+    if (Callee->hasSemanticsAttrs() &&
+        WhatToInline == InlineSelection::Everything) {
+      if (Callee->hasSemanticsAttrThatStartsWith("inline_late") && IsInStdlib) {
+        return nullptr;
+      }
+    }
+
   } else if (Callee->isGlobalInit()) {
     if (WhatToInline != InlineSelection::Everything) {
       return nullptr;

test/SILOptimizer/inline_late.sil

@@ -0,0 +1,37 @@
+// RUN: %target-sil-opt -assume-parsing-unqualified-ownership-sil -enable-sil-verify-all %s -early-inline -sil-inline-threshold=50 | %FileCheck %s
+// RUN: %target-sil-opt -assume-parsing-unqualified-ownership-sil -enable-sil-verify-all %s -late-inline -sil-inline-threshold=50 | %FileCheck %s --check-prefix=LATE
+// RUN: %target-sil-opt -assume-parsing-unqualified-ownership-sil -enable-sil-verify-all %s -late-inline -sil-inline-threshold=50 -module-name Swift | %FileCheck %s --check-prefix=STDLIBLATE
+
+sil_stage canonical
+
+import Builtin
+
+sil [_semantics "inline_late"] @inline_late_func : $@convention(thin) () -> Builtin.Int32 {
+bb0:
+  %0 = integer_literal $Builtin.Int32, 3
+  return %0 : $Builtin.Int32
+}
+
+//CHECK-LABEL: caller_func5
+//CHECK: function_ref
+//CHECK: apply
+//CHECK-NEXT: ret
+
+//STDLIBLATE-LABEL: caller_func5
+//STDLIBLATE: function_ref
+//STDLIBLATE: apply
+//STDLIBLATE-NEXT: ret
+
+
+//LATE-LABEL: caller_func5
+//LATE: integer_literal
+//LATE-NOT: function_ref
+//LATE-NOT: apply
+//LATE-NEXT: ret
+
+sil @caller_func5 : $@convention(thin) () -> Builtin.Int32 {
+bb0:
+  %0 = function_ref @inline_late_func : $@convention(thin) () -> Builtin.Int32
+  %1 = apply %0() : $@convention(thin) () -> Builtin.Int32
+  return %1 : $Builtin.Int32
+}