MemBehavior: handle begin_access when checking for apply side-effects.

Author: eeckstein

lib/SILOptimizer/Analysis/MemoryBehavior.cpp

@@ -364,6 +364,7 @@ static bool hasEscapingUses(SILValue address, int &numChecks) {
       case SILInstructionKind::CopyAddrInst:
       case SILInstructionKind::DestroyAddrInst:
       case SILInstructionKind::DeallocStackInst:
+      case SILInstructionKind::EndAccessInst:
         // Those instructions have no result and cannot escape the address.
         break;
       case SILInstructionKind::ApplyInst:
@@ -373,6 +374,7 @@ static bool hasEscapingUses(SILValue address, int &numChecks) {
         // possible that an address, passed as an indirect parameter, escapes
         // the function in any way (which is not unsafe and undefined behavior).
         break;
+      case SILInstructionKind::BeginAccessInst:
       case SILInstructionKind::OpenExistentialAddrInst:
       case SILInstructionKind::UncheckedTakeEnumDataAddrInst:
       case SILInstructionKind::StructElementAddrInst:

test/SILOptimizer/mem-behavior.sil

@@ -269,7 +269,6 @@ bb2(%8 : $Error):
   unreachable
 }
 
-
 // CHECK-LABEL:  @beginapply_allocstack_and_copyaddr
 // CHECK:        PAIR #0.
 // CHECK-NEXT:       (%4, %5) = begin_apply %3(%0) : $@yield_once @convention(thin) (@in Int32) -> @yields Int32
@@ -324,6 +323,23 @@ bb0(%0 : $X):
   return %3 : $Int32
 }
 
+// CHECK-LABEL: @apply_and_begin_access
+// CHECK:       PAIR #0.
+// CHECK-NEXT:      %6 = apply %5(%1) : $@convention(thin) (@in Int32) -> Int32
+// CHECK-NEXT:    %0 = argument of bb0 : $*Int32
+// CHECK-NEXT:    r=0,w=0
+sil @apply_and_begin_access : $@convention(thin) (@in Int32) -> Int32 {
+bb0(%0 : $*Int32):
+  %1 = alloc_stack $Int32
+  %2 = begin_access [read] [static] %0 : $*Int32
+  copy_addr %2 to %1 : $*Int32
+  end_access %2 : $*Int32
+  %5 = function_ref @single_indirect_arg : $@convention(thin) (@in Int32) -> Int32
+  %6 = apply %5(%1) : $@convention(thin) (@in Int32) -> Int32
+  dealloc_stack %1 : $*Int32
+  return %6 : $Int32
+}
+
 sil @load_from_in : $@convention(thin) (@in X) -> () {
 bb0(%0 : $*X):
   %1 = load %0 : $*X