Revert "Add new pattern in SILCombine to optimize redundant thick to objc metatype conversions (#31595)"

This reverts commit 488333c.

It looks like this might have caused a heap-use-after free on an asan
bot.

rdar://63135437

Author: aschwaighofer

lib/SILOptimizer/SILCombiner/SILCombinerCastVisitors.cpp

@@ -452,10 +452,6 @@ SILCombiner::visitThickToObjCMetatypeInst(ThickToObjCMetatypeInst *TTOCMI) {
   if (CastOpt.optimizeMetatypeConversion(TTOCMI, MetatypeRepresentation::Thick))
     MadeChange = true;
 
-  if (auto *OCTTMI = dyn_cast<ObjCToThickMetatypeInst>(TTOCMI->getOperand())) {
-    TTOCMI->replaceAllUsesWith(OCTTMI->getOperand());
-    return eraseInstFromFunction(*TTOCMI);
-  }
   return nullptr;
 }
 
@@ -476,10 +472,6 @@ SILCombiner::visitObjCToThickMetatypeInst(ObjCToThickMetatypeInst *OCTTMI) {
   if (CastOpt.optimizeMetatypeConversion(OCTTMI, MetatypeRepresentation::ObjC))
     MadeChange = true;
 
-  if (auto *TTOCMI = dyn_cast<ThickToObjCMetatypeInst>(OCTTMI->getOperand())) {
-    OCTTMI->replaceAllUsesWith(TTOCMI->getOperand());
-    return eraseInstFromFunction(*OCTTMI);
-  }
   return nullptr;
 }
 

test/SILOptimizer/peephole_thick_to_objc_metatype.sil

@@ -8,8 +8,6 @@ import Builtin
 import Swift
 import SwiftShims
 
-import Foundation
-
 @objc(XX) protocol X {
 }
 
@@ -117,48 +115,3 @@ bb0(%0 : $T):
   strong_release %0 : $T
   return %3 : $@thick T.Type
 }
-
-// CHECK-LABEL: sil @$test_peephole_objc_to_thick_to_objc :
-// CHECK: [[T:%.*]] = apply
-// CHECK-NOT: objc_to_thick_metatype
-// CHECK-NOT: thick_to_objc_metatype
-// CHECK: enum $Optional<@objc_metatype AnyObject.Type>, #Optional.some!enumelt, [[T]] : $@objc_metatype AnyObject.Type
-// CHECK: } // end sil function '$test_peephole_objc_to_thick_to_objc'
-
-sil @$test_peephole_objc_to_thick_to_objc : $@convention(thin) (@guaranteed NSObject) -> Optional<UnsafeMutablePointer<OpaquePointer>> {
-// %0 "obj"                                       // users: %3, %2, %1
-bb0(%0 : $NSObject):
-  debug_value %0 : $NSObject, let, name "obj", argno 1 // id: %1
-  %2 = objc_method %0 : $NSObject, #NSObject.classForCoder!getter.foreign : (NSObject) -> () -> AnyObject.Type, $@convention(objc_method) (NSObject) -> @objc_metatype AnyObject.Type // user: %3
-  %3 = apply %2(%0) : $@convention(objc_method) (NSObject) -> @objc_metatype AnyObject.Type // user: %4
-  %4 = objc_to_thick_metatype %3 : $@objc_metatype AnyObject.Type to $@thick AnyObject.Type // users: %6, %5
-  debug_value %4 : $@thick AnyObject.Type, let, name "c" // id: %5
-  %6 = thick_to_objc_metatype %4 : $@thick AnyObject.Type to $@objc_metatype AnyObject.Type // user: %7
-  %7 = enum $Optional<@objc_metatype AnyObject.Type>, #Optional.some!enumelt, %6 : $@objc_metatype AnyObject.Type // user: %10
-  %8 = enum $Optional<UnsafeMutablePointer<UInt32>>, #Optional.none!enumelt // user: %10
-  // function_ref class_copyMethodList
-  %9 = function_ref @class_copyMethodList : $@convention(c) (Optional<@objc_metatype AnyObject.Type>, Optional<UnsafeMutablePointer<UInt32>>) -> Optional<UnsafeMutablePointer<OpaquePointer>> // user: %10
-  %10 = apply %9(%7, %8) : $@convention(c) (Optional<@objc_metatype AnyObject.Type>, Optional<UnsafeMutablePointer<UInt32>>) -> Optional<UnsafeMutablePointer<OpaquePointer>> // users: %12, %11
-  debug_value %10 : $Optional<UnsafeMutablePointer<OpaquePointer>>, let, name "l" // id: %11
-  return %10 : $Optional<UnsafeMutablePointer<OpaquePointer>> // id: %12
-}
-
-// CHECK-LABEL: sil @$test_peephole_thick_to_objc_to_thick :
-// CHECK: [[T:%.*]] = apply
-// CHECK-NOT: thick_to_objc_metatype
-// CHECK-NOT: objc_to_thick_metatype
-// CHECK: return [[T]]
-// CHECK: } // end sil function '$test_peephole_thick_to_objc_to_thick'
-
-sil @$test_peephole_thick_to_objc_to_thick : $@convention(thin) (@guaranteed AnyObject) -> @thick AnyObject.Type {
-bb0(%0 : $AnyObject):
-  %func = function_ref @foo : $@convention(thin) (@guaranteed AnyObject) -> @thick AnyObject.Type
-  %res = apply %func(%0) : $@convention(thin) (@guaranteed AnyObject) -> @thick AnyObject.Type
-  %objctype = thick_to_objc_metatype %res : $@thick AnyObject.Type to $@objc_metatype AnyObject.Type
-  %thicktype = objc_to_thick_metatype %objctype : $@objc_metatype AnyObject.Type to $@thick AnyObject.Type
-  return %thicktype :  $@thick AnyObject.Type
-}
-
-// class_copyMethodList
-sil [serializable] [clang class_copyMethodList] @class_copyMethodList : $@convention(c) (Optional<@objc_metatype AnyObject.Type>, Optional<UnsafeMutablePointer<UInt32>>) -> Optional<UnsafeMutablePointer<OpaquePointer>>
-sil [serializable] @foo : $@convention(thin) (@guaranteed AnyObject) -> @thick AnyObject.Type