Merge pull request #41522 from apple/revert-41518-revert-41497-lexical_lifetimes/lexical_destroy_addr_hoisting/split-copy_addr

Revert "Revert "[SSADestroyHoisting] Split destroy from copy.""

Author: nate-chandler

lib/SILOptimizer/Transforms/SSADestroyHoisting.cpp

@@ -754,6 +754,7 @@ void SSADestroyHoisting::run() {
   llvm::SmallVector<AllocStackInst *, 4> asis;
   llvm::SmallVector<BeginAccessInst *, 4> bais;
   llvm::SmallVector<StoreInst *, 4> sis;
+  llvm::SmallVector<CopyAddrInst *, 4> cais;
 
   // Collect the instructions that we'll be transforming.
   for (auto &block : *getFunction()) {
@@ -768,6 +769,10 @@ void SSADestroyHoisting::run() {
         if (si->getOwnershipQualifier() == StoreOwnershipQualifier::Assign) {
           sis.push_back(si);
         }
+      } else if (auto *cai = dyn_cast<CopyAddrInst>(&inst)) {
+        if (cai->isInitializationOfDest() == IsNotInitialization) {
+          cais.push_back(cai);
+        }
       }
     }
   }
@@ -804,6 +809,32 @@ void SSADestroyHoisting::run() {
     remainingDestroyAddrs.insert(dai);
     ++splitDestroys;
   }
+  // Similarly, also expand each
+  //
+  //     copy_addr to
+  //
+  // instruction into
+  //
+  //     destroy_addr
+  //     copy_addr to [initialization]
+  //
+  // sequences to create still more destroy_addrs to hoist.
+  //
+  // As above, record the newly created destroy_addrs and copy_addrs off of
+  // which they were split.  After hoisting, we'll merge them back together when
+  // possible.
+  llvm::SmallVector<std::pair<DestroyAddrInst *, CopyAddrInst *>, 8>
+      splitDestroysAndCopies;
+  for (auto *cai : cais) {
+    auto builder = SILBuilderWithScope(cai);
+    auto *dai = builder.createDestroyAddr(
+        RegularLocation::getAutoGeneratedLocation(cai->getLoc()),
+        cai->getOperand(1));
+    cai->setIsInitializationOfDest(IsInitialization);
+    splitDestroysAndCopies.push_back({dai, cai});
+    remainingDestroyAddrs.insert(dai);
+    ++splitDestroys;
+  }
 
   // We assume that the function is in reverse post order so visiting the
   // blocks and pushing begin_access as we see them and then popping them off
@@ -840,17 +871,29 @@ void SSADestroyHoisting::run() {
     if (!remainingDestroyAddrs.contains(dai))
       continue;
     auto *si = pair.second;
-    if (dai->getNextInstruction() == si) {
-      // No stores should have been rewritten during hoisting.  Their ownership
-      // qualifiers were set to [init] when splitting off the destroy_addrs.
-      assert(si->getOwnershipQualifier() == StoreOwnershipQualifier::Init);
-      // If a newly created destroy_addr has not been hoisted from its previous
-      // location, combine it back together with the store [init] which it was
-      // split off from.
-      deleter.forceDelete(dai);
-      si->setOwnershipQualifier(StoreOwnershipQualifier::Assign);
-      --splitDestroys;
-    }
+    if (dai->getNextInstruction() != si)
+      continue;
+    // No stores should have been rewritten during hoisting.  Their ownership
+    // qualifiers were set to [init] when splitting off the destroy_addrs.
+    assert(si->getOwnershipQualifier() == StoreOwnershipQualifier::Init);
+    // If a newly created destroy_addr has not been hoisted from its previous
+    // location, combine it back together with the store [init] which it was
+    // split off from.
+    deleter.forceDelete(dai);
+    si->setOwnershipQualifier(StoreOwnershipQualifier::Assign);
+    --splitDestroys;
+  }
+  for (auto pair : splitDestroysAndCopies) {
+    auto *dai = pair.first;
+    if (!remainingDestroyAddrs.contains(dai))
+      continue;
+    auto *cai = pair.second;
+    if (dai->getNextInstruction() != cai)
+      continue;
+    assert(cai->isInitializationOfDest() == IsInitialization);
+    deleter.forceDelete(dai);
+    cai->setIsInitializationOfDest(IsNotInitialization);
+    --splitDestroys;
   }
   // If there were any destroy_addrs split off of stores and not recombined
   // with them, then the function has changed.