Updates to MemAccessUtils to handle borrowed address returns

Author: meg-gupta

include/swift/SIL/MemAccessUtils.h

@@ -164,6 +164,14 @@ inline SILValue stripAccessMarkers(SILValue v) {
   return v;
 }
 
+inline bool isGuaranteedAddressReturn(SILValue value) {
+  auto *defInst = dyn_cast_or_null<ApplyInst>(value->getDefiningInstruction());
+  if (!defInst) {
+    return false;
+  }
+  return defInst->getSubstCalleeConv().hasGuaranteedAddressResults();
+}
+
 /// Return the source address after stripping as many access projections as
 /// possible without losing the address type.
 ///
@@ -1802,6 +1810,12 @@ Result AccessUseDefChainVisitor<Impl, Result>::visit(SILValue sourceAddr) {
     if (isExternalGlobalAddressor(cast<ApplyInst>(sourceAddr)))
       return asImpl().visitUnidentified(sourceAddr);
 
+    if (isGuaranteedAddressReturn(sourceAddr)) {
+      return asImpl().visitAccessProjection(
+          cast<ApplyInst>(sourceAddr),
+          &cast<ApplyInst>(sourceAddr)->getSelfArgumentOperand());
+    }
+
     // Don't currently allow any other calls to return an accessed address.
     return asImpl().visitNonAccess(sourceAddr);
   }

lib/SIL/Utils/MemAccessUtils.cpp

@@ -1416,7 +1416,8 @@ class AccessPathVisitor : public FindAccessVisitorImpl<AccessPathVisitor> {
              // copyable_to_moveonlywrapper_addr, we just look through it when
              // we see it
              || isa<MoveOnlyWrapperToCopyableAddrInst>(projectedAddr) ||
-             isa<CopyableToMoveOnlyWrapperAddrInst>(projectedAddr));
+             isa<CopyableToMoveOnlyWrapperAddrInst>(projectedAddr) ||
+             isGuaranteedAddressReturn(projectedAddr));
     }
     return sourceAddr->get();
   }
@@ -2029,6 +2030,9 @@ bool AccessPathDefUseTraversal::visitUser(DFSEntry dfs) {
         && visitSingleValueUser(svi, dfs) == IgnoredUse) {
       return true;
     }
+    if (isGuaranteedAddressReturn(svi)) {
+      pushUsers(svi, dfs);
+    }
   }
   if (auto *sbi = dyn_cast<StoreBorrowInst>(use->getUser())) {
     if (use->get() == sbi->getDest()) {
@@ -2038,6 +2042,7 @@ bool AccessPathDefUseTraversal::visitUser(DFSEntry dfs) {
   if (isa<EndBorrowInst>(use->getUser())) {
     return true;
   }
+
   // We weren't able to "see through" any more address conversions; so
   // record this as a use.