[ShrinkBorrowScope] Return modified copy_values.

So that CopyPropagation and other clients can react accordingly, pass
back a list of copy_value instructions that were rewritten by
ShrinkBorrowScope.  In CopyPropagation, add each modified copy to the
copy worklist.

Author: nate-chandler

include/swift/SILOptimizer/Utils/CanonicalizeBorrowScope.h

@@ -147,7 +147,9 @@ class CanonicalizeBorrowScope {
   bool consolidateBorrowScope();
 };
 
-bool shrinkBorrowScope(BeginBorrowInst *bbi, InstructionDeleter &deleter);
+bool shrinkBorrowScope(
+    BeginBorrowInst *bbi, InstructionDeleter &deleter,
+    SmallVectorImpl<CopyValueInst *> &modifiedCopyValueInsts);
 
 } // namespace swift
 

lib/SILOptimizer/Transforms/CopyPropagation.cpp

@@ -438,7 +438,10 @@ void CopyPropagation::run() {
   //       blocks and pushing begin_borrows as we see them and then popping them
   //       off the end will result in shrinking inner borrow scopes first.
   while (auto *bbi = beginBorrowsToShrink.pop()) {
-    changed |= shrinkBorrowScope(bbi, deleter);
+    SmallVector<CopyValueInst *, 4> modifiedCopyValueInsts;
+    changed |= shrinkBorrowScope(bbi, deleter, modifiedCopyValueInsts);
+    for (auto *cvi : modifiedCopyValueInsts)
+      defWorklist.updateForCopy(cvi);
   }
   deleter.cleanupDeadInstructions();
 

lib/SILOptimizer/Utils/ShrinkBorrowScope.cpp

@@ -47,6 +47,8 @@ class ShrinkBorrowScope {
 
   InstructionDeleter &deleter;
 
+  SmallVectorImpl<CopyValueInst *> &modifiedCopyValueInsts;
+
   SmallPtrSet<SILInstruction *, 16> users;
   llvm::SmallVector<std::pair<SILBasicBlock *, SILInstruction *>>
       barrierInstructions;
@@ -66,8 +68,10 @@ class ShrinkBorrowScope {
   llvm::SmallDenseMap<SILBasicBlock *, SILInstruction *> startingInstructions;
 
 public:
-  ShrinkBorrowScope(BeginBorrowInst *bbi, InstructionDeleter &deleter)
-      : introducer(bbi), deleter(deleter) {}
+  ShrinkBorrowScope(BeginBorrowInst *bbi, InstructionDeleter &deleter,
+                    SmallVectorImpl<CopyValueInst *> &modifiedCopyValueInsts)
+      : introducer(bbi), deleter(deleter),
+        modifiedCopyValueInsts(modifiedCopyValueInsts) {}
 
   bool run();
 
@@ -156,6 +160,7 @@ class ShrinkBorrowScope {
           auto borrowee = introducer->getOperand();
           if (auto *cvi = dyn_cast<CopyValueInst>(argument)) {
             cvi->setOperand(borrowee);
+            modifiedCopyValueInsts.push_back(cvi);
           } else {
             apply.setArgument(index, borrowee);
           }
@@ -172,6 +177,7 @@ class ShrinkBorrowScope {
         if (canReplaceValueWithBorrowedValue(cvi->getOperand())) {
           auto borrowee = introducer->getOperand();
           cvi->setOperand(borrowee);
+          modifiedCopyValueInsts.push_back(cvi);
           return true;
         }
       }
@@ -318,8 +324,9 @@ void ShrinkBorrowScope::createEndBorrow(SILInstruction *insertionPoint) {
       introducer);
 }
 
-bool swift::shrinkBorrowScope(BeginBorrowInst *bbi,
-                              InstructionDeleter &deleter) {
-  ShrinkBorrowScope borrowShrinker(bbi, deleter);
+bool swift::shrinkBorrowScope(
+    BeginBorrowInst *bbi, InstructionDeleter &deleter,
+    SmallVectorImpl<CopyValueInst *> &modifiedCopyValueInsts) {
+  ShrinkBorrowScope borrowShrinker(bbi, deleter, modifiedCopyValueInsts);
   return borrowShrinker.run();
 }