[SemanticARCOpts] Remove unnecessary borrow scope for @guaranteed function arg when used as a phi operand

Author: meg-gupta

lib/SILOptimizer/SemanticARC/OwnedToGuaranteedPhiOpt.cpp

@@ -251,13 +251,6 @@ bool swift::semanticarc::tryConvertOwnedPhisToGuaranteedPhis(Context &ctx) {
     while (!incomingValueOperandList.empty()) {
       auto incomingValueOperand = incomingValueOperandList.pop_back_val();
       SILValue originalValue = originalIncomingValues.pop_back_val();
-      if (incomingValueOperand.isGuaranteedConsuming() &&
-          isa<SILFunctionArgument>(originalValue) &&
-          originalValue->getOwnershipKind() == OwnershipKind::Guaranteed) {
-        auto loc = RegularLocation::getAutoGeneratedLocation();
-        SILBuilderWithScope builder(incomingValueOperand.getInst());
-        originalValue = builder.createBeginBorrow(loc, originalValue);
-      }
       incomingValueOperand.getOperand()->set(originalValue);
     }
 

lib/SILOptimizer/SemanticARC/OwnershipLiveRange.cpp

@@ -310,16 +310,7 @@ void OwnershipLiveRange::convertJoinedLiveRangePhiToGuaranteed(
     InstModCallbacks callbacks) && {
 
   // First convert the phi value itself to be guaranteed.
-  SILValue phiValue = convertIntroducerToGuaranteed(introducer);
-
-  // Then insert end_borrows at each of our destroys if we are consuming. We
-  // have to convert the phi to guaranteed first since otherwise, the ownership
-  // check when we create the end_borrows will trigger.
-  if (auto *phi = dyn_cast<SILPhiArgument>(phiValue)) {
-    if (!isGuaranteedForwardingPhi(phi)) {
-      insertEndBorrowsAtDestroys(phiValue, deadEndBlocks, scratch);
-    }
-  }
+  convertIntroducerToGuaranteed(introducer);
 
   // Then eliminate all of the destroys...
   while (!destroyingUses.empty()) {