Fix copy_value to have 'None' side-effects.

Copies can be moved as much as you like as long as OSSA is legal.

This fixes some instruction deletion utilities for OSSA and any other
utilities that check side effects. Copies are common.

It also finally allows pure functions to be CSE'd!

include/swift/SIL/SILNodes.def

@@ -582,8 +582,10 @@ ABSTRACT_VALUE_AND_INST(SingleValueInstruction, ValueBase, SILInstruction)
                     SingleValueInstruction, MayHaveSideEffects, DoesNotRelease)
   SINGLE_VALUE_INST(CopyBlockWithoutEscapingInst, copy_block_without_escaping,
                     SingleValueInstruction, MayHaveSideEffects, DoesNotRelease)
+  // A copy_value's retain semantics are fully encapsulated in OSSA
+  // invariants. It has no side effects relative to other OSSA values.
   SINGLE_VALUE_INST(CopyValueInst, copy_value,
-                    SingleValueInstruction, MayHaveSideEffects, DoesNotRelease)
+                    SingleValueInstruction, None, DoesNotRelease)
 #define UNCHECKED_REF_STORAGE(Name, name, ...) \
   SINGLE_VALUE_INST(StrongCopy##Name##ValueInst, strong_copy_##name##_value, \
                     SingleValueInstruction, MayHaveSideEffects, DoesNotRelease)

test/SILOptimizer/cse_apply_ossa.sil

@@ -122,11 +122,11 @@ bb0(%0 : $Int64):
   return %14 : $Int64
 }
 
-// CHECK-LABEL: sil [ossa] @dont_cse_retain_only_apply :
-// CHECK: %{{[0-9]+}} = apply
-// CHECK: %{{[0-9]+}} = apply
-// CHECK-LABEL:} // end sil function 'dont_cse_retain_only_apply'
-sil [ossa] @dont_cse_retain_only_apply : $@convention(thin) () -> () {
+// CHECK-LABEL: sil [ossa] @cse_retain_only_apply :
+// CHECK: apply
+// CHECK-NOT: apply
+// CHECK-LABEL:} // end sil function 'cse_retain_only_apply'
+sil [ossa] @cse_retain_only_apply : $@convention(thin) () -> () {
 bb0:
   %f = function_ref @retain_only : $@convention(thin) () -> @owned XX
   %a1 = apply %f() : $@convention(thin) () -> @owned XX
@@ -169,7 +169,7 @@ bb0(%0 : @guaranteed $Klass):
 
 // CHECK-LABEL: sil [ossa] @apply_nontrivial_test2 :
 // CHECK: apply
-// CHECK: apply
+// CHECK-NOT: apply
 // CHECK-LABEL:} // end sil function 'apply_nontrivial_test2'
 sil [ossa] @apply_nontrivial_test2 : $@convention(thin) (@guaranteed Klass) -> () {
 bb0(%0 : @guaranteed $Klass):

test/SILOptimizer/sil_combine_ossa.sil

@@ -772,14 +772,18 @@ sil [ossa] @unbalanced_closure : $@convention(thin) (@guaranteed B) -> ()
 // CHECK-NOT: partial_apply
 // Check that the arguments of the closure are released after its last use
 // CHECK-NEXT: destroy_value %0 : $B
-// CHECK-NEXT: unreachable
+// CHECK-NEXT: tuple
+// CHECK-NEXT: return
 // CHECK: } // end sil function 'partial_apply_unbalanced_retain_release'
 sil [ossa] @partial_apply_unbalanced_retain_release : $@convention(thin) (@owned B) -> () {
 bb0(%0 : @owned $B):
   %1 = function_ref @unbalanced_closure : $@convention(thin) (@guaranteed B) -> ()
   %2 = partial_apply %1(%0) : $@convention(thin) (@guaranteed B) -> ()
   %2a = copy_value %2 : $@callee_owned () -> ()
-  unreachable
+  destroy_value %2 : $@callee_owned () -> ()
+  destroy_value %2a  : $@callee_owned () -> ()
+  %99 = tuple ()
+  return %99 : $()
 }
 
 class C1 {}