[SILInliner] Borrow guaranteed yields.

When inlining a begin_apply, if one of the values is yielded by
guaranteed convention, if the yielded value is itself owned, borrow it
during inlining.

Doing so is necessary because users of the yielded value are expecting a
value with guaranteed ownership.  For example, it's valid to
store_borrow such a value but not an owned value.

Author: nate-chandler

lib/SILOptimizer/Utils/SILInliner.cpp

@@ -162,8 +162,20 @@ class BeginApplySite {
       auto calleeYields = yield->getYieldedValues();
       auto callerYields = BeginApply->getYieldedValues();
       assert(calleeYields.size() == callerYields.size());
+      SmallVector<BeginBorrowInst *, 2> guaranteedYields;
       for (auto i : indices(calleeYields)) {
         auto remappedYield = getMappedValue(calleeYields[i]);
+        // When owned values are yielded @guaranteed, the mapped value must be
+        // borrowed and the result be substituted in place of the originally
+        // yielded value.  Otherwise, there could be uses of the original value
+        // which require an @guaranteed operand into which we'd be attempting to
+        // substitute an @owned operand.
+        if (calleeYields[i]->getOwnershipKind() == OwnershipKind::Owned &&
+            !yield->getOperandRef(i).isConsuming()) {
+          auto *bbi = Builder->createBeginBorrow(Loc, remappedYield);
+          guaranteedYields.push_back(bbi);
+          remappedYield = bbi;
+        }
         callerYields[i]->replaceAllUsesWith(remappedYield);
       }
       Builder->createBranch(Loc, returnToBB);
@@ -172,11 +184,17 @@ class BeginApplySite {
       if (EndApply) {
         SavedInsertionPointRAII savedIP(*Builder, EndApplyBB);
         auto resumeBB = remapBlock(yield->getResumeBB());
+        for (auto *bbi : guaranteedYields) {
+          Builder->createEndBorrow(EndApply->getLoc(), bbi);
+        }
         Builder->createBranch(EndApply->getLoc(), resumeBB);
       }
       if (AbortApply) {
         SavedInsertionPointRAII savedIP(*Builder, AbortApplyBB);
         auto unwindBB = remapBlock(yield->getUnwindBB());
+        for (auto *bbi : guaranteedYields) {
+          Builder->createEndBorrow(EndApply->getLoc(), bbi);
+        }
         Builder->createBranch(AbortApply->getLoc(), unwindBB);
       }
       return true;

test/SILOptimizer/inline_begin_apply.sil

@@ -44,6 +44,23 @@ unwind:
   unwind
 }
 
+sil [ossa] @getSomeClass : $@convention(thin) () -> @owned SomeClass
+
+sil [transparent] [ossa] @yield_owned_as_guaranteed : $@yield_once @convention(thin) () -> @yields @guaranteed SomeClass {
+  %getSomeClass = function_ref @getSomeClass : $@convention(thin) () -> @owned SomeClass
+  %SomeClass = apply %getSomeClass() : $@convention(thin) () -> @owned SomeClass
+  yield %SomeClass : $SomeClass, resume bb1, unwind bb2
+
+bb1:
+  destroy_value %SomeClass : $SomeClass
+  %retval = tuple ()
+  return %retval : $()
+
+bb2:
+  destroy_value %SomeClass : $SomeClass
+  unwind
+}
+
 sil [transparent] [ossa] @test_unreachable : $@yield_once <C: SomeClass> () -> (@yields @in Indirect<C>) {
 entry:
   unreachable 
@@ -555,3 +572,48 @@ bb2:
   return %ret : $()
 }
 
+
+// CHECK-LABEL: sil [ossa] @test_store_borrow_owned_as_guaranteed_yield : {{.*}} {
+// CHECK:       {{bb[0-9]+}}:
+// CHECK:         [[ADDR:%[^,]+]] = alloc_stack $SomeClass
+// CHECK:         [[INSTANCE:%[^,]+]] = apply
+// CHECK:         [[LIFETIME:%[^,]+]] = begin_borrow [[INSTANCE]]
+// CHECK:         [[BORROW:%[^,]+]] = store_borrow [[LIFETIME]] to [[ADDR]]
+// CHECK:         yield [[BORROW]] {{.*}}, resume [[BB_RESUME:bb[0-9]+]], unwind [[BB_UNWIND:bb[0-9]+]]
+// CHECK:       [[BB_RESUME]]:
+// CHECK:         end_borrow [[BORROW]]
+// CHECK:         dealloc_stack [[ADDR]]
+// CHECK:         end_borrow [[LIFETIME]]
+// CHECK:         destroy_value [[INSTANCE]]
+// CHECK:         tuple ()
+// CHECK:         [[RETVAL:%[^,]+]] = tuple ()
+// CHECK:         return [[RETVAL]]
+// CHECK:       [[BB_UNWIND]]:
+// CHECK:         end_borrow [[BORROW]]
+// CHECK:         dealloc_stack [[ADDR]]
+// CHECK:         end_borrow [[LIFETIME]]
+// CHECK:         destroy_value [[INSTANCE]]
+// CHECK:         unwind
+// CHECK-LABEL: } // end sil function 'test_store_borrow_owned_as_guaranteed_yield'
+sil [ossa] @test_store_borrow_owned_as_guaranteed_yield : $@yield_once @convention(thin) @substituted <T> () -> @yields @in_guaranteed T for <SomeClass> {
+entry:
+  %addr = alloc_stack $SomeClass
+  %callee = function_ref @yield_owned_as_guaranteed : $@yield_once @convention(thin) () -> @yields @guaranteed SomeClass
+  (%instance, %token) = begin_apply %callee() : $@yield_once @convention(thin) () -> @yields @guaranteed SomeClass
+  %borrow = store_borrow %instance to %addr : $*SomeClass
+  yield %borrow : $*SomeClass, resume bb_resume, unwind bb_unwind
+
+bb_resume:
+  end_borrow %borrow : $*SomeClass
+  dealloc_stack %addr : $*SomeClass
+  end_apply %token
+  %retval = tuple ()
+  return %retval : $()
+
+bb_unwind:
+  end_borrow %borrow : $*SomeClass
+  dealloc_stack %addr : $*SomeClass
+  abort_apply %token
+  unwind
+
+}