Merge pull request #40458 from nate-chandler/loop-rotate/dont-reborrow-when-ownership-forwarded

[LoopRotate] Don't phi forwarded guaranteed value.

Author: nate-chandler

lib/SILOptimizer/LoopTransforms/LoopRotate.cpp

@@ -69,6 +69,7 @@ canDuplicateOrMoveToPreheader(SILLoop *loop, SILBasicBlock *preheader,
   llvm::DenseSet<SILInstruction *> invariants;
   int cost = 0;
   for (auto &instRef : *bb) {
+    OwnershipForwardingMixin *ofm = nullptr;
     auto *inst = &instRef;
     if (auto *MI = dyn_cast<MethodInst>(inst)) {
       if (MI->getMember().isForeign)
@@ -95,6 +96,9 @@ canDuplicateOrMoveToPreheader(SILLoop *loop, SILBasicBlock *preheader,
     } else if (isa<IntegerLiteralInst>(inst)) {
       moves.push_back(inst);
       invariants.insert(inst);
+    } else if ((ofm = OwnershipForwardingMixin::get(inst)) &&
+               ofm->getForwardingOwnershipKind() == OwnershipKind::Guaranteed) {
+      return false;
     } else if (!inst->mayHaveSideEffects() && !inst->mayReadFromMemory()
                && !isa<TermInst>(inst) && !isa<AllocationInst>(inst)
                && /* not marked mayhavesideffects */

test/SILOptimizer/looprotate_nontrivial_ossa.sil

@@ -8,6 +8,10 @@ class Klass {
 
 }
 
+struct BoxStruct {
+    var guts: Klass
+}
+
 sil [ossa] @useKlass : $@convention(thin) (@guaranteed Klass) -> ()
 
 sil [ossa] @klassIdentity : $@convention(thin) (@owned Klass) -> @owned Klass
@@ -195,3 +199,52 @@ exit:
   %retval = tuple ()
   return %retval : $()
 }
+
+// A guaranteed value whose ownership has been forwarded must not be reborrowed. 
+//
+// CHECK-LABEL: sil [ossa] @forwarded_borrow_cant_be_reborrowed : $@convention(thin) (@owned BoxStruct) -> () {
+// CHECK-NOT:   {{bb[0-9]+}}({{%[^,]+}} : @guaranteed $BoxStruct, {{%[^,]+}} : @guaranteed $Klass):
+// CHECK-LABEL: } // end sil function 'forwarded_borrow_cant_be_reborrowed'
+sil [ossa] @forwarded_borrow_cant_be_reborrowed : $@convention(thin) (@owned BoxStruct) -> () {
+bb0(%0 : @owned $BoxStruct):
+  br bb1
+
+bb1:
+  %2 = integer_literal $Builtin.Int1, 0
+  cond_br %2, bb2, bb3
+
+bb2:
+  br bb10
+
+bb3:
+  %5 = begin_borrow %0 : $BoxStruct
+  %6 = struct_extract %5 : $BoxStruct, #BoxStruct.guts
+  %7 = integer_literal $Builtin.Int1, 0
+  cond_br %7, bb4, bb5
+
+bb4:
+  unreachable
+
+bb5:
+  %10 = begin_borrow %6 : $Klass
+  end_borrow %10 : $Klass
+  end_borrow %5 : $BoxStruct
+  br bb6
+
+bb6:
+  br bb7
+
+
+bb7:
+  %16 = integer_literal $Builtin.Int1, -1
+  cond_br %16, bb8, bb9
+
+bb8:
+  br bb10
+
+bb9:
+  br bb1
+
+bb10:
+  unreachable
+}