[PATCH] D56235: Teach ObjCARC optimizer about equivalent PHIs when eliminating autoreleaseRV/retainRV pairs

[Pete Cooper via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
pete marked an inline comment as done.
Closed by commit rL350284: Teach ObjCARC optimizer about equivalent PHIs when eliminating… (authored by pete, committed by ).

Changed prior to commit:
  https://reviews.llvm.org/D56235?vs=179971&id=179987#toc

Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D56235/new/

https://reviews.llvm.org/D56235

Files:
  llvm/trunk/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
  llvm/trunk/test/Transforms/ObjCARC/rv.ll


Index: llvm/trunk/test/Transforms/ObjCARC/rv.ll
===================================================================
--- llvm/trunk/test/Transforms/ObjCARC/rv.ll
+++ llvm/trunk/test/Transforms/ObjCARC/rv.ll
@@ -239,6 +239,24 @@
   ret i8* %p
 }
 
+; Delete autoreleaseRV+retainRV pairs when they have equivalent PHIs as inputs
+
+; CHECK: define i8* @test19phi(i8* %p) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br label %test19bb
+; CHECK: test19bb:
+; CHECK-NEXT: ret i8* %p
+define i8* @test19phi(i8* %p) {
+entry:
+  br label %test19bb
+test19bb:
+  %phi1 = phi i8* [ %p, %entry ]
+  %phi2 = phi i8* [ %p, %entry ]
+  call i8* @llvm.objc.autoreleaseReturnValue(i8* %phi1)
+  call i8* @llvm.objc.retainAutoreleasedReturnValue(i8* %phi2)
+  ret i8* %p
+}
+
 ; Like test19 but with plain autorelease.
 
 ; CHECK: define i8* @test20(i8* %p) {
Index: llvm/trunk/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
===================================================================
--- llvm/trunk/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
+++ llvm/trunk/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
@@ -600,6 +600,17 @@
     }
   }
 
+  // Track PHIs which are equivalent to our Arg.
+  SmallDenseSet<const Value*, 2> EquivalentArgs;
+  EquivalentArgs.insert(Arg);
+
+  // Add PHIs that are equivalent to Arg to ArgUsers.
+  if (const PHINode *PN = dyn_cast<PHINode>(Arg)) {
+    SmallVector<const Value *, 2> ArgUsers;
+    getEquivalentPHIs(*PN, ArgUsers);
+    EquivalentArgs.insert(ArgUsers.begin(), ArgUsers.end());
+  }
+
   // Check for being preceded by an objc_autoreleaseReturnValue on the same
   // pointer. In this case, we can delete the pair.
   BasicBlock::iterator I = RetainRV->getIterator(),
@@ -609,7 +620,7 @@
       --I;
     while (I != Begin && IsNoopInstruction(&*I));
     if (GetBasicARCInstKind(&*I) == ARCInstKind::AutoreleaseRV &&
-        GetArgRCIdentityRoot(&*I) == Arg) {
+        EquivalentArgs.count(GetArgRCIdentityRoot(&*I))) {
       Changed = true;
       ++NumPeeps;
 


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