[llvm] r315914 - [ObjCARC] Do not move a release that has the clang.imprecise_release tag

[Akira Hatanaka via llvm-commits]

Author: ahatanak
Date: Mon Oct 16 09:46:59 2017
New Revision: 315914

URL: http://llvm.org/viewvc/llvm-project?rev=315914&view=rev
Log:
[ObjCARC] Do not move a release that has the clang.imprecise_release tag
above PHI instructions.

ARC optimizer has an optimization that moves a call to an ObjC runtime
function above a phi instruction when the phi has a null operand and is
an argument passed to the function call. This optimization should not
kick in when the runtime function is an objc_release that releases an
object with precise lifetime semantics.

rdar://problem/34959669

Modified:
    llvm/trunk/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
    llvm/trunk/test/Transforms/ObjCARC/basic.ll

Modified: llvm/trunk/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ObjCARC/ObjCARCOpts.cpp?rev=315914&r1=315913&r2=315914&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/ObjCARC/ObjCARCOpts.cpp (original)
+++ llvm/trunk/lib/Transforms/ObjCARC/ObjCARCOpts.cpp Mon Oct 16 09:46:59 2017
@@ -808,9 +808,14 @@ void ObjCARCOpt::OptimizeIndividualCalls
 
     // If Arg is a PHI, and one or more incoming values to the
     // PHI are null, and the call is control-equivalent to the PHI, and there
-    // are no relevant side effects between the PHI and the call, the call
-    // could be pushed up to just those paths with non-null incoming values.
-    // For now, don't bother splitting critical edges for this.
+    // are no relevant side effects between the PHI and the call, and the call
+    // is not a release that doesn't have the clang.imprecise_release tag, the
+    // call could be pushed up to just those paths with non-null incoming
+    // values. For now, don't bother splitting critical edges for this.
+    if (Class == ARCInstKind::Release &&
+        !Inst->getMetadata(MDKindCache.get(ARCMDKindID::ImpreciseRelease)))
+      continue;
+
     SmallVector<std::pair<Instruction *, const Value *>, 4> Worklist;
     Worklist.push_back(std::make_pair(Inst, Arg));
     do {

Modified: llvm/trunk/test/Transforms/ObjCARC/basic.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/ObjCARC/basic.ll?rev=315914&r1=315913&r2=315914&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/ObjCARC/basic.ll (original)
+++ llvm/trunk/test/Transforms/ObjCARC/basic.ll Mon Oct 16 09:46:59 2017
@@ -1345,6 +1345,26 @@ B:
 C:
   %h = phi double* [ null, %A ], [ %p, %B ]
   %c = bitcast double* %h to i8*
+  call void @objc_release(i8* %c), !clang.imprecise_release !0
+  ret void
+}
+
+; Do not move an objc_release that doesn't have the clang.imprecise_release tag.
+
+; CHECK-LABEL: define void @test22_precise(
+; CHECK: %[[P0:.*]] = phi double*
+; CHECK: %[[V0:.*]] = bitcast double* %[[P0]] to i8*
+; CHECK: call void @objc_release(i8* %[[V0]])
+; CHECK: ret void
+define void @test22_precise(double* %p, i1 %a) {
+  br i1 %a, label %A, label %B
+A:
+  br label %C
+B:
+  br label %C
+C:
+  %h = phi double* [ null, %A ], [ %p, %B ]
+  %c = bitcast double* %h to i8*
   call void @objc_release(i8* %c)
   ret void
 }