[sil-combine] Update fix_lifetime opts for ownership

The one opt we perform here is that we promote fix_lifetime on loadable
alloc_stack addresses to fix_lifetimes on objects by loading the underlying
value and putting the fix lifetime upon it.

Author: gottesmm

lib/SILOptimizer/SILCombiner/SILCombinerMiscVisitors.cpp

@@ -1849,17 +1849,17 @@ SILInstruction *SILCombiner::visitTupleExtractInst(TupleExtractInst *TEI) {
   return nullptr;
 }
 
-SILInstruction *SILCombiner::visitFixLifetimeInst(FixLifetimeInst *FLI) {
-  if (FLI->getFunction()->hasOwnership())
-    return nullptr;
-
+SILInstruction *SILCombiner::visitFixLifetimeInst(FixLifetimeInst *fli) {
   // fix_lifetime(alloc_stack) -> fix_lifetime(load(alloc_stack))
-  Builder.setCurrentDebugScope(FLI->getDebugScope());
-  if (auto *AI = dyn_cast<AllocStackInst>(FLI->getOperand())) {
-    if (FLI->getOperand()->getType().isLoadable(*FLI->getFunction())) {
-      auto Load = Builder.createLoad(FLI->getLoc(), AI,
-                                     LoadOwnershipQualifier::Unqualified);
-      return Builder.createFixLifetime(FLI->getLoc(), Load);
+  Builder.setCurrentDebugScope(fli->getDebugScope());
+  if (auto *ai = dyn_cast<AllocStackInst>(fli->getOperand())) {
+    if (fli->getOperand()->getType().isLoadable(*fli->getFunction())) {
+      // load when ossa is disabled
+      auto load = Builder.emitLoadBorrowOperation(fli->getLoc(), ai);
+      Builder.createFixLifetime(fli->getLoc(), load);
+      // no-op when ossa is disabled
+      Builder.emitEndBorrowOperation(fli->getLoc(), load);
+      return eraseInstFromFunction(*fli);
     }
   }
   return nullptr;

test/SILOptimizer/sil_combine_misc_visitor_opts_ossa.sil

@@ -0,0 +1,50 @@
+// RUN: %target-sil-opt -enable-objc-interop -enforce-exclusivity=none -enable-sil-verify-all %s -sil-combine -sil-combine-disable-alloc-stack-opts | %FileCheck %s
+
+sil_stage canonical
+
+import Builtin
+
+class Klass {}
+
+// We test both the ossa and non-ossa variants.
+//
+// CHECK-LABEL: sil [ossa] @fix_lifetime_promotion_ossa : $@convention(thin) (@owned Klass) -> () {
+// CHECK: bb0([[ARG:%.*]] :
+// CHECK:   [[STACK:%.*]] = alloc_stack $Klass
+// CHECK:   store [[ARG]] to [init] [[STACK]]
+// CHECK:   [[BORROW:%.*]] = load_borrow [[STACK]]
+// CHECK:   fix_lifetime [[BORROW]]
+// CHECK:   end_borrow [[BORROW]]
+// CHECK:   destroy_addr [[STACK]]
+// CHECK:   dealloc_stack [[STACK]]
+// CHECK: } // end sil function 'fix_lifetime_promotion_ossa'
+sil [ossa] @fix_lifetime_promotion_ossa : $@convention(thin) (@owned Klass) -> () {
+bb0(%0 : @owned $Klass):
+  %1 = alloc_stack $Klass
+  store %0 to [init] %1 : $*Klass
+  fix_lifetime %1 : $*Klass
+  destroy_addr %1 : $*Klass
+  dealloc_stack %1 : $*Klass
+  %9999 = tuple()
+  return %9999 : $()
+}
+
+// CHECK-LABEL: sil @fix_lifetime_promotion : $@convention(thin) (@owned Klass) -> () {
+// CHECK: bb0([[ARG:%.*]] :
+// CHECK:   [[STACK:%.*]] = alloc_stack $Klass
+// CHECK:   store [[ARG]] to [[STACK]]
+// CHECK:   [[BORROW:%.*]] = load [[STACK]]
+// CHECK:   fix_lifetime [[BORROW]]
+// CHECK:   destroy_addr [[STACK]]
+// CHECK:   dealloc_stack [[STACK]]
+// CHECK: } // end sil function 'fix_lifetime_promotion'
+sil @fix_lifetime_promotion : $@convention(thin) (@owned Klass) -> () {
+bb0(%0 : $Klass):
+  %1 = alloc_stack $Klass
+  store %0 to %1 : $*Klass
+  fix_lifetime %1 : $*Klass
+  destroy_addr %1 : $*Klass
+  dealloc_stack %1 : $*Klass
+  %9999 = tuple()
+  return %9999 : $()
+}