Swift Optimizer: make some SILCombine optimizations available for the "Simplification" pass

* begin_cow_mutation
* global_value
* strong_retain and strong_release

So far, those simplifications did only run in SILCombine. Now they are also considered in the swift Simplification pass.

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/InstructionSimplification/SimplifyBeginCOWMutation.swift

@@ -12,7 +12,7 @@
 
 import SIL
 
-extension BeginCOWMutationInst : SILCombineSimplifyable {
+extension BeginCOWMutationInst : Simplifyable, SILCombineSimplifyable {
   func simplify(_ context: SimplifyContext) {
 
     /// The buffer of an empty Array/Set/Dictionary singleton is known to be not

SwiftCompilerSources/Sources/Optimizer/InstructionSimplification/SimplifyGlobalValue.swift

@@ -18,7 +18,7 @@ import SIL
 // Note that `simplifyStrongRetainPass` and `simplifyStrongReleasePass` can
 // even remove "unbalanced" retains/releases of a `global_value`, but this
 // requires a minimum deployment target.
-extension GlobalValueInst : SILCombineSimplifyable {
+extension GlobalValueInst : Simplifyable, SILCombineSimplifyable {
   func simplify(_ context: SimplifyContext) {
     var users = Stack<Instruction>(context)
     defer { users.deinitialize() }

SwiftCompilerSources/Sources/Optimizer/InstructionSimplification/SimplifyStrongRetainRelease.swift

@@ -12,7 +12,7 @@
 
 import SIL
 
-extension StrongRetainInst : SILCombineSimplifyable {
+extension StrongRetainInst : Simplifyable, SILCombineSimplifyable {
   func simplify(_ context: SimplifyContext) {
     if isNotReferenceCounted(value: operand) {
       context.erase(instruction: self)
@@ -44,7 +44,7 @@ extension StrongRetainInst : SILCombineSimplifyable {
   }
 }
 
-extension StrongReleaseInst : SILCombineSimplifyable {
+extension StrongReleaseInst : Simplifyable, SILCombineSimplifyable {
   func simplify(_ context: SimplifyContext) {
     let op = operand
     if isNotReferenceCounted(value: op) {