Remove borrow scope adjustment for @guaranteed phi args

Author: meg-gupta

include/swift/SILOptimizer/Utils/BasicBlockOptUtils.h

@@ -284,7 +284,7 @@ class BasicBlockCloner : public SILCloner<BasicBlockCloner> {
   /// WARNING: If client converts terminator results to phis (e.g. replaces a
   /// switch_enum with a branch), then it must call this before performing that
   /// transformation, or fix the OSSA representation of that value itself.
-  void updateOSSAAfterCloning();
+  void updateSSAAfterCloning();
 
   /// Get the newly cloned block corresponding to `origBB`.
   SILBasicBlock *getNewBB() {
@@ -294,13 +294,6 @@ class BasicBlockCloner : public SILCloner<BasicBlockCloner> {
   bool wasCloned() { return isBlockCloned(origBB); }
 
 protected:
-  /// Helper function to perform SSA updates used by updateOSSAAfterCloning.
-  void updateSSAAfterCloning(SmallVectorImpl<SILPhiArgument *> &newPhis);
-
-  /// Given a terminator result, either from the original or the cloned block,
-  /// update OSSA for any phis created for the result during edge splitting.
-  void updateOSSATerminatorResult(SILPhiArgument *termResult);
-
   // MARK: CRTP overrides.
 
   /// Override getMappedValue to allow values defined outside the block to be

lib/SILOptimizer/Transforms/SimplifyCFG.cpp

@@ -245,7 +245,7 @@ bool SimplifyCFG::threadEdge(const ThreadInfo &ti) {
           dyn_cast<BranchInst>(ThreadedSuccessorBlock->getTerminator())) {
     simplifyBranchBlock(branchInst);
   }
-  Cloner.updateOSSAAfterCloning();
+  Cloner.updateSSAAfterCloning();
   return true;
 }
 
@@ -1030,7 +1030,7 @@ bool SimplifyCFG::tryJumpThreading(BranchInst *BI) {
   // Duplicate the destination block into this one, rewriting uses of the BBArgs
   // to use the branch arguments as we go.
   Cloner.cloneBranchTarget(BI);
-  Cloner.updateOSSAAfterCloning();
+  Cloner.updateSSAAfterCloning();
 
   // Once all the instructions are copied, we can nuke BI itself.  We also add
   // the threaded and edge block to the worklist now that they (likely) can be
@@ -2856,7 +2856,7 @@ bool SimplifyCFG::tailDuplicateObjCMethodCallSuccessorBlocks() {
       continue;
 
     Cloner.cloneBranchTarget(Branch);
-    Cloner.updateOSSAAfterCloning();
+    Cloner.updateSSAAfterCloning();
 
     Changed = true;
     // Simplify the cloned block and continue tail duplicating through its new

lib/SILOptimizer/Utils/BasicBlockOptUtils.cpp

@@ -147,67 +147,8 @@ bool swift::canCloneTerminator(TermInst *termInst) {
   return true;
 }
 
-/// Given a terminator result, either from the original or the cloned block,
-/// update OSSA for any phis created for the result during edge splitting.
-void BasicBlockCloner::updateOSSATerminatorResult(SILPhiArgument *termResult) {
-  assert(termResult->isTerminatorResult() && "precondition");
-
-  // If the terminator result is used by a phi, then it is invalid OSSA
-  // which was created by edge splitting.
-  for (Operand *termUse : termResult->getUses()) {
-    if (auto phiOper = PhiOperand(termUse)) {
-      createBorrowScopeForPhiOperands(phiOper.getValue());
-    }
-  }
-}
-
-// Cloning does not invalidate ownership lifetime. When it clones values, it
-// also either clones the consumes, or creates the necessary phis that consume
-// the new values on all paths.  However, cloning may create new phis of
-// inner guaranteed values. Since phis are reborrows, they are only allowed to
-// use BorrowedValues. Therefore, we must create nested borrow scopes for any
-// new phis whose arguments aren't BorrowedValues. Note that other newly created
-// phis are themselves BorrowedValues, so only one level of nested borrow is
-// needed per value, per new phi that the value reaches.
-void BasicBlockCloner::updateOSSAAfterCloning() {
+void BasicBlockCloner::updateSSAAfterCloning() {
   SmallVector<SILPhiArgument *, 4> updateSSAPhis;
-  if (!origBB->getParent()->hasOwnership()) {
-    updateSSAAfterCloning(updateSSAPhis);
-    return;
-  }
-
-  // If the original basic block has terminator results, then all phis in the
-  // exit blocks are new phis that used to be terminator results.
-  //
-  // Create nested borrow scopes for terminator results that were converted to
-  // phis during edge splitting. This is simpler to check before SSA update.
-  //
-  // This assumes that the phis introduced by update-SSA below cannot be users
-  // of the phis that were created in exitBBs during block cloning. Otherwise
-  // borrowPhiArguments would handle them twice.
-  auto *termInst = origBB->getTerminator();
-  // FIXME: cond_br args should not exist in OSSA
-  if (!isa<BranchInst>(termInst) && !isa<CondBranchInst>(termInst)) {
-    // Update all of the terminator results.
-    for (auto *succBB : origBB->getSuccessorBlocks()) {
-      for (SILArgument *termResult : succBB->getArguments()) {
-        updateOSSATerminatorResult(cast<SILPhiArgument>(termResult));
-      }
-    }
-  }
-
-  // Update SSA form before calling OSSA update utilities to maintain a layering
-  // of SIL invariants.
-  updateSSAAfterCloning(updateSSAPhis);
-
-  // Create nested borrow scopes for phis created during SSA update.
-  for (auto *phi : updateSSAPhis) {
-    createBorrowScopeForPhiOperands(phi);
-  }
-}
-
-void BasicBlockCloner::updateSSAAfterCloning(
-    SmallVectorImpl<SILPhiArgument *> &newPhis) {
   // All instructions should have been checked by canCloneInstruction. But we
   // still need to check the arguments.
   for (auto arg : origBB->getArguments()) {
@@ -218,7 +159,7 @@ void BasicBlockCloner::updateSSAAfterCloning(
   if (!needsSSAUpdate)
     return;
 
-  SILSSAUpdater ssaUpdater(&newPhis);
+  SILSSAUpdater ssaUpdater(&updateSSAPhis);
   for (auto availValPair : availVals) {
     auto inst = availValPair.first;
     if (inst->use_empty())

lib/SILOptimizer/Utils/CheckedCastBrJumpThreading.cpp

@@ -321,7 +321,7 @@ void CheckedCastBrJumpThreading::Edit::modifyCFGForFailurePreds(
     replaceBranchTarget(TI, CCBBlock, TargetFailureBB,
     /*PreserveArgs=*/true);
   }
-  Cloner.updateOSSAAfterCloning();
+  Cloner.updateSSAAfterCloning();
 }
 
 /// Create a copy of the BB or reuse BB as a landing basic block for all
@@ -383,7 +383,7 @@ void CheckedCastBrJumpThreading::Edit::modifyCFGForSuccessPreds(
     SILBuilderWithScope Builder(clonedCCBI);
     Builder.createBranch(clonedCCBI->getLoc(), successBB, {SuccessArg});
     clonedCCBI->eraseFromParent();
-    Cloner.updateOSSAAfterCloning();
+    Cloner.updateSSAAfterCloning();
     return;
   }
   // Remove all uses from the failure path so RAUW can erase the
@@ -395,7 +395,7 @@ void CheckedCastBrJumpThreading::Edit::modifyCFGForSuccessPreds(
   // Create nested borrow scopes for new phis either created for the
   // checked_cast's results or during SSA update. This puts the SIL in
   // valid OSSA form before calling OwnershipRAUWHelper.
-  Cloner.updateOSSAAfterCloning();
+  Cloner.updateSSAAfterCloning();
 
   auto *clonedSuccessArg = successBB->getArgument(0);
   OwnershipRAUWHelper rauwUtil(rauwContext, clonedSuccessArg, SuccessArg);
@@ -786,7 +786,7 @@ void CheckedCastBrJumpThreading::optimizeFunction() {
     edit->modifyCFGForSuccessPreds(Cloner, rauwContext);
 
     if (Cloner.wasCloned()) {
-      Cloner.updateOSSAAfterCloning();
+      Cloner.updateSSAAfterCloning();
 
       if (!Cloner.getNewBB()->pred_empty())
         BlocksForWorklist.push_back(Cloner.getNewBB());