[semantic-arc] Add __swift_endBorrow support to LLVMPasses and make sure it is removed by LLVMARCContract.cpp.

Author: gottesmm

lib/LLVMPasses/LLVMARCContract.cpp

@@ -273,9 +273,10 @@ bool SwiftARCContractImpl::run() {
       case RT_UnknownReleaseN:
       case RT_BridgeReleaseN:
         llvm_unreachable("These are only created by LLVMARCContract !");
-      // Delete all fix lifetime instructions. After llvm-ir they have no use
-      // and show up as calls in the final binary.
+      // Delete all fix lifetime and end borrow instructions. After llvm-ir they
+      // have no use and show up as calls in the final binary.
       case RT_FixLifetime:
+      case RT_EndBorrow:
         Inst.eraseFromParent();
         ++NumNoopDeleted;
         continue;

lib/LLVMPasses/LLVMARCOpts.cpp

@@ -102,6 +102,7 @@ static bool canonicalizeInputFunction(Function &F, ARCEntryPointBuilder &B,
       case RT_BridgeRelease:
       case RT_AllocObject:
       case RT_FixLifetime:
+      case RT_EndBorrow:
       case RT_NoMemoryAccessed:
       case RT_RetainUnowned:
       case RT_CheckUnowned:
@@ -368,6 +369,7 @@ static bool performLocalReleaseMotion(CallInst &Release, BasicBlock &BB,
     }
 
     case RT_FixLifetime:
+    case RT_EndBorrow:
     case RT_RetainUnowned:
     case RT_CheckUnowned:
     case RT_Unknown:
@@ -441,6 +443,7 @@ static bool performLocalRetainMotion(CallInst &Retain, BasicBlock &BB,
       break;
 
     case RT_FixLifetime: // This only stops release motion. Retains can move over it.
+    case RT_EndBorrow:
       break;
 
     case RT_Retain:
@@ -588,6 +591,7 @@ static DtorKind analyzeDestructor(Value *P) {
       case RT_NoMemoryAccessed:
       case RT_AllocObject:
       case RT_FixLifetime:
+      case RT_EndBorrow:
       case RT_CheckUnowned:
         // Skip over random instructions that don't touch memory in the caller.
         continue;
@@ -717,6 +721,7 @@ static bool performStoreOnlyObjectElimination(CallInst &Allocation,
     case RT_Release:
     case RT_Retain:
     case RT_FixLifetime:
+    case RT_EndBorrow:
     case RT_CheckUnowned:
       // It is perfectly fine to eliminate various retains and releases of this
       // object: we are zapping all accesses or none.

lib/LLVMPasses/LLVMSwift.def

@@ -129,6 +129,15 @@ SWIFT_FUNC(BridgeRelease, ModRef, bridgeObjectRelease)
 /// void swift_bridgeObjectRelease_n(%swift.refcounted* %P)
 SWIFT_FUNC(BridgeReleaseN, ModRef, bridgeObjectRelease_n)
 
+/// borrow source is the value that was borrowed from. borrow_dest is the
+/// borrowed ref.
+///
+/// TODO: We may want to communicate to the optimizer that this does not have
+/// global effects.
+///
+/// void __swift_endBorrow(i8* %borrow_source, i8* %borrow_dest)
+SWIFT_INTERNAL_FUNC_NEVER_NONATOMIC(EndBorrow, ModRef, endBorrow)
+
 /// This is not a runtime function that we support.  Maybe it is not a call,
 /// or is a call to something we don't care about.
 KIND(Unknown, ModRef)

lib/LLVMPasses/LLVMSwiftRCIdentity.cpp

@@ -57,6 +57,7 @@ SwiftRCIdentity::stripReferenceForwarding(llvm::Value *Val) {
   case RT_RetainUnowned:
   case RT_CheckUnowned:
   case RT_ObjCRelease:
+  case RT_EndBorrow:
     break;
   // ObjC forwards references.
   case RT_ObjCRetain:

test/LLVMPasses/contract.ll

@@ -19,6 +19,7 @@ declare void @noread_user(%swift.refcounted*) readnone
 declare void @user(%swift.refcounted*)
 declare void @noread_user_bridged(%swift.bridge*) readnone
 declare void @user_bridged(%swift.bridge*)
+declare void @__swift_endBorrow(i8*, i8*)
 
 ; CHECK-LABEL: define{{( protected)?}} void @fixlifetime_removal(i8*) {
 ; CHECK-NOT: call void @__swift_fixLifetime
@@ -29,6 +30,14 @@ entry:
   ret void
 }
 
+; CHECK-LABEL: define{{( protected)?}} void @endBorrow_removal(i8*, i8*) {
+; CHECK-NOT: call void @__swift_endBorrow
+define void @endBorrow_removal(i8*, i8*) {
+entry:
+  call void @__swift_endBorrow(i8* %0, i8* %1)
+  ret void
+}
+
 ; CHECK-LABEL: define{{( protected)?}} %swift.refcounted* @swift_contractRetainN(%swift.refcounted* %A) {
 ; CHECK: entry:
 ; CHECK-NEXT: br i1 undef