MemBehavior: handle guaranteed arguments in non-OSSA mode.

In non-OSSA, this is the only case for which we know that if an instruction is within a "borrow-scope".

Author: eeckstein

lib/SILOptimizer/Analysis/MemoryBehavior.cpp

@@ -566,6 +566,17 @@ static SILValue getBeginScopeInst(SILValue V) {
   if (BorrowedValue borrowedObj = getSingleBorrowIntroducingValue(object)) {
     return borrowedObj.value;
   }
+  if (!object->getFunction()->hasOwnership()) {
+    // In non-OSSA, do a quick check if the object is a guaranteed function
+    // argument.
+    // Note that in OSSA, getSingleBorrowIntroducingValue will detect a
+    // guaranteed argument.
+    SILValue root = findOwnershipReferenceAggregate(object);
+    if (auto *funcArg = dyn_cast<SILFunctionArgument>(root)) {
+      if (funcArg->getArgumentConvention().isGuaranteedConvention())
+        return funcArg;
+    }
+  }
   return SILValue();
 }
 

test/SILOptimizer/mem-behavior.sil

@@ -618,6 +618,19 @@ bb0(%0 : @guaranteed $X):
   return %3 : $Int32
 }
 
+// CHECK-LABEL: @testNonOSSAImmutableRefWithGuaranteedParam
+// CHECK:      PAIR #1.
+// CHECK-NEXT:     %4 = apply %3() : $@convention(thin) () -> ()
+// CHECK-NEXT:     %1 = ref_element_addr [immutable] %0 : $X, #X.a
+// CHECK-NEXT:   r=1,w=0
+sil @testNonOSSAImmutableRefWithGuaranteedParam : $@convention(thin) (@guaranteed X) -> Int32 {
+bb0(%0 : $X):
+  %1 = ref_element_addr [immutable] %0 : $X, #X.a
+  %3 = load %1 : $*Int32
+  %5 = function_ref @nouser_func : $@convention(thin) () -> ()
+  %6 = apply %5() : $@convention(thin) () -> ()
+  return %3 : $Int32
+}
 // CHECK-LABEL: @testImmutableRefWithBorrow
 // CHECK:      PAIR #1.
 // CHECK-NEXT:     %5 = apply %4() : $@convention(thin) () -> ()