Revert "Update ConditionForwarding for @guaranteed forwarding phi support"

This reverts commit 4acfd4d.

Author: meg-gupta

lib/SILOptimizer/Transforms/ConditionForwarding.cpp

@@ -202,14 +202,6 @@ bool ConditionForwarding::tryOptimize(SwitchEnumInst *SEI) {
     if (!EI)
       return false;
 
-    if (getFunction()->hasOwnership() && EI->hasOperand()) {
-      auto some = EI->getOperand();
-      if (some->getOwnershipKind() == OwnershipKind::Guaranteed &&
-          isa<SILFunctionArgument>(some)) {
-        return false;
-      }
-    }
-
     if (CommonBranchBlock && PredPred != CommonBranchBlock)
       return false;
     CommonBranchBlock = PredPred;

test/SILOptimizer/conditionforwarding_nontrivial_ossa.sil

@@ -71,8 +71,7 @@ bb6:
   return %r : $()
 }
 
-// Currently, this is not optimized away because enum has @guaranteed function
-// argument, which  will need a borrow scope before being forwarded.
+// Currently, this is not optimized away because memory behavior of begin_borrow is conservative
 // CHECK-LABEL: sil [ossa] @simple_forwarding2 :
 // CHECK: switch_enum
 // CHECK-LABEL: } // end sil function 'simple_forwarding2'
@@ -82,11 +81,13 @@ bb0(%0 : $Builtin.Int1, %1 : @guaranteed $Klass):
 
 bb1:
   %2 = enum $E, #E.A!enumelt, %1 : $Klass
-  br bb3(%2 : $E)
+  %borrow2 = begin_borrow %2 : $E
+  br bb3(%borrow2 : $E)
 
 bb2:
   %3 = enum $E, #E.B!enumelt, %1 : $Klass
-  br bb3(%3 : $E)
+  %borrow3 = begin_borrow %3 : $E
+  br bb3(%borrow3 : $E)
 
 bb3(%14 : @guaranteed $E):
   %15 = function_ref @callee : $@convention(thin) () -> ()
@@ -100,6 +101,7 @@ bb5(%18 : @guaranteed $Klass):
   br bb6
 
 bb6:
+  end_borrow %14 : $E
   %r = tuple ()
   return %r : $()
 }
@@ -185,19 +187,22 @@ bb6:
 
 // CHECK-LABEL: sil [ossa] @simple_switch_enum_forwarding2 : 
 // CHECK: switch_enum
+// CHECK: switch_enum
 // CHECK-LABEL: } // end sil function 'simple_switch_enum_forwarding2'
 sil [ossa] @simple_switch_enum_forwarding2 : $@convention(thin) (@guaranteed E3) -> () {
 bb0(%0 : @guaranteed $E3):
   switch_enum %0 : $E3, case #E3.A!enumelt: bb1, default bb2
 
 bb1(%1 : @guaranteed $Klass):
   %2 = enum $E, #E.A!enumelt, %1 : $Klass
-  br bb3(%2 : $E)
+  %borrow2 = begin_borrow %2 : $E
+  br bb3(%borrow2 : $E)
 
 bb2(%defaultenum : @guaranteed $E3):
   %defaultklass = unchecked_enum_data %defaultenum : $E3, #E3.B!enumelt
   %3 = enum $E, #E.B!enumelt, %defaultklass : $Klass
-  br bb3(%3 : $E)
+  %borrow3 = begin_borrow %3 : $E
+  br bb3(%borrow3 : $E)
 
 bb3(%14 : @guaranteed $E):
   %15 = function_ref @callee : $@convention(thin) () -> ()
@@ -211,6 +216,7 @@ bb5(%5 : @guaranteed $Klass):
   br bb6
 
 bb6:
+  end_borrow %14 : $E
   %r = tuple ()
   return %r : $()
 }