Merge pull request swiftlang#71942 from jckarter/reenable-borrow-to-destructure-transform

Reenable BorrowToDestructureTransform during the MoveOnlyAddressChecker.

Author: jckarter

lib/SILOptimizer/Mandatory/MoveOnlyAddressCheckerUtils.cpp

@@ -2194,25 +2194,23 @@ bool GatherUsesVisitor::visitUse(Operand *op) {
     unsigned numDiagnostics =
       moveChecker.diagnosticEmitter.getDiagnosticCount();
 
-    // Before we do anything, run the borrow to destructure transform in case
-    // we have a switch_enum user.
-    if (!getASTContext().LangOpts.hasFeature(Feature::BorrowingSwitch)) {
-      BorrowToDestructureTransform borrowToDestructure(
-          moveChecker.allocator, markedValue, li, moveChecker.diagnosticEmitter,
-          moveChecker.poa);
-      if (!borrowToDestructure.transform()) {
-        assert(moveChecker.diagnosticEmitter
-                   .didEmitCheckerDoesntUnderstandDiagnostic());
-        LLVM_DEBUG(llvm::dbgs()
-                   << "Failed to perform borrow to destructure transform!\n");
-        return false;
-      }
-      // If we emitted an error diagnostic, do not transform further and instead
-      // mark that we emitted an early diagnostic and return true.
-      if (numDiagnostics != moveChecker.diagnosticEmitter.getDiagnosticCount()) {
-        LLVM_DEBUG(llvm::dbgs() << "Emitting borrow to destructure error!\n");
-        return true;
-      }
+    // Before we do anything, run the borrow to destructure transform to reduce
+    // copies through borrows.
+    BorrowToDestructureTransform borrowToDestructure(
+        moveChecker.allocator, markedValue, li, moveChecker.diagnosticEmitter,
+        moveChecker.poa);
+    if (!borrowToDestructure.transform()) {
+      assert(moveChecker.diagnosticEmitter
+                 .didEmitCheckerDoesntUnderstandDiagnostic());
+      LLVM_DEBUG(llvm::dbgs()
+                 << "Failed to perform borrow to destructure transform!\n");
+      return false;
+    }
+    // If we emitted an error diagnostic, do not transform further and instead
+    // mark that we emitted an early diagnostic and return true.
+    if (numDiagnostics != moveChecker.diagnosticEmitter.getDiagnosticCount()) {
+      LLVM_DEBUG(llvm::dbgs() << "Emitting borrow to destructure error!\n");
+      return true;
     }
 
     // Now, validate that what we will transform into a take isn't a take that

test/SILOptimizer/moveonly_borrowing_switch_mode_with_partial_consume.swift

@@ -0,0 +1,18 @@
+// RUN: %target-swift-frontend -emit-sil -verify -enable-experimental-feature BorrowingSwitch -enable-experimental-feature MoveOnlyPartialConsumption -parse-as-library %s
+
+func foo() {
+    let node = Node()
+    bar(node.next)
+}
+
+struct Node: ~Copyable {
+    var next: Link
+
+    init() { fatalError() }
+}
+
+struct Link: ~Copyable {}
+
+func bar(_: consuming Link) {}
+
+