[ObjCARC] Do not turn a call to @objc_autoreleaseReturnValue into a call
to @objc_autorelease if its operand is a PHI and the PHI has an
equivalent value that is used by a return instruction.
For example, ARC optimizer shouldn't replace the call in the following
example, as doing so breaks the AutoreleaseRV/RetainRV optimization:
%v1 = bitcast i32* %v0 to i8*
br label %bb3
bb2:
%v3 = bitcast i32* %v2 to i8*
br label %bb3
bb3:
%p = phi i8* [ %v1, %bb1 ], [ %v3, %bb2 ]
%retval = phi i32* [ %v0, %bb1 ], [ %v2, %bb2 ] ; equivalent to %p
%v4 = tail call i8* @objc_autoreleaseReturnValue(i8* %p)
ret i32* %retval
Also, make sure ObjCARCContract replaces @objc_autoreleaseReturnValue's
operand uses with its value so that the call gets tail-called.
rdar://problem/15894705
llvm-svn: 323009
diff --git a/llvm/lib/Transforms/ObjCARC/ObjCARC.h b/llvm/lib/Transforms/ObjCARC/ObjCARC.h
index cd9b3d9..745dac8 100644
--- a/llvm/lib/Transforms/ObjCARC/ObjCARC.h
+++ b/llvm/lib/Transforms/ObjCARC/ObjCARC.h
@@ -82,6 +82,26 @@
return dyn_cast<InvokeInst>(Opnd);
}
+/// Return the list of PHI nodes that are equivalent to PN.
+template<class PHINodeTy, class VectorTy>
+void getEquivalentPHIs(PHINodeTy &PN, VectorTy &PHIList) {
+ auto *BB = PN.getParent();
+ for (auto &P : BB->phis()) {
+ if (&P == &PN) // Do not add PN to the list.
+ continue;
+ unsigned I = 0, E = PN.getNumIncomingValues();
+ for (; I < E; ++I) {
+ auto *BB = PN.getIncomingBlock(I);
+ auto *PNOpnd = PN.getIncomingValue(I)->stripPointerCasts();
+ auto *POpnd = P.getIncomingValueForBlock(BB)->stripPointerCasts();
+ if (PNOpnd != POpnd)
+ break;
+ }
+ if (I == E)
+ PHIList.push_back(&P);
+ }
+}
+
} // end namespace objcarc
} // end namespace llvm
diff --git a/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp b/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp
index c4e6121..5deb394 100644
--- a/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp
+++ b/llvm/lib/Transforms/ObjCARC/ObjCARCContract.cpp
@@ -618,8 +618,17 @@
else if (isa<GlobalAlias>(Arg) &&
!cast<GlobalAlias>(Arg)->isInterposable())
Arg = cast<GlobalAlias>(Arg)->getAliasee();
- else
+ else {
+ // If Arg is a PHI node, get PHIs that are equivalent to it and replace
+ // their uses.
+ if (PHINode *PN = dyn_cast<PHINode>(Arg)) {
+ SmallVector<Value *, 1> PHIList;
+ getEquivalentPHIs(*PN, PHIList);
+ for (Value *PHI : PHIList)
+ ReplaceArgUses(PHI);
+ }
break;
+ }
}
// Replace bitcast users of Arg that are dominated by Inst.
diff --git a/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp b/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
index 99ed686..ecec854 100644
--- a/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
+++ b/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
@@ -652,6 +652,11 @@
SmallVector<const Value *, 2> Users;
Users.push_back(Ptr);
+
+ // Add PHIs that are equivalent to Ptr to Users.
+ if (const PHINode *PN = dyn_cast<PHINode>(Ptr))
+ getEquivalentPHIs(*PN, Users);
+
do {
Ptr = Users.pop_back_val();
for (const User *U : Ptr->users()) {
diff --git a/llvm/test/Transforms/ObjCARC/contract-replace-arg-use.ll b/llvm/test/Transforms/ObjCARC/contract-replace-arg-use.ll
index 26b0cd9..4cff9f7 100644
--- a/llvm/test/Transforms/ObjCARC/contract-replace-arg-use.ll
+++ b/llvm/test/Transforms/ObjCARC/contract-replace-arg-use.ll
@@ -6,6 +6,7 @@
; Check that ARC contraction replaces the function return with the value
; returned by @objc_autoreleaseReturnValue.
+; CHECK-LABEL: define i32* @autoreleaseRVTailCall(
; CHECK: %[[V0:[0-9]+]] = tail call i8* @objc_autoreleaseReturnValue(
; CHECK: %[[V1:[0-9]+]] = bitcast i8* %[[V0]] to i32*
; CHECK: ret i32* %[[V1]]
@@ -16,3 +17,30 @@
%3 = tail call i8* @objc_autoreleaseReturnValue(i8* %1)
ret i32* %2
}
+
+declare i32* @foo2(i32);
+
+; CHECK-LABEL: define i32* @autoreleaseRVTailCallPhi(
+; CHECK: %[[PHIVAL:.*]] = phi i8* [ %{{.*}}, %bb1 ], [ %{{.*}}, %bb2 ]
+; CHECK: %[[RETVAL:.*]] = phi i32* [ %{{.*}}, %bb1 ], [ %{{.*}}, %bb2 ]
+; CHECK: %[[V4:.*]] = tail call i8* @objc_autoreleaseReturnValue(i8* %[[PHIVAL]])
+; CHECK: %[[V0:.*]] = bitcast i8* %[[V4]] to i32*
+; CHECK: ret i32* %[[V0]]
+
+define i32* @autoreleaseRVTailCallPhi(i1 %cond) {
+entry:
+ br i1 %cond, label %bb1, label %bb2
+bb1:
+ %v0 = call i32* @foo2(i32 1)
+ %v1 = bitcast i32* %v0 to i8*
+ br label %bb3
+bb2:
+ %v2 = call i32* @foo2(i32 2)
+ %v3 = bitcast i32* %v2 to i8*
+ br label %bb3
+bb3:
+ %phival = phi i8* [ %v1, %bb1 ], [ %v3, %bb2 ]
+ %retval = phi i32* [ %v0, %bb1 ], [ %v2, %bb2 ]
+ %v4 = tail call i8* @objc_autoreleaseReturnValue(i8* %phival)
+ ret i32* %retval
+}
diff --git a/llvm/test/Transforms/ObjCARC/rv.ll b/llvm/test/Transforms/ObjCARC/rv.ll
index d84a875..425f86c 100644
--- a/llvm/test/Transforms/ObjCARC/rv.ll
+++ b/llvm/test/Transforms/ObjCARC/rv.ll
@@ -333,6 +333,37 @@
ret i8* %v2
}
+declare i32* @func27(i32);
+
+; Check that ObjCARCOpt::OptimizeAutoreleaseRVCall doesn't turn a call to
+; @objc_autoreleaseReturnValue into a call to @objc_autorelease when a return
+; instruction uses a value equivalent to @objc_autoreleaseReturnValue's operand.
+; In the code below, %phival and %retval are considered equivalent.
+
+; CHECK-LABEL: define i32* @test27(
+; CHECK: %[[PHIVAL:.*]] = phi i8* [ %{{.*}}, %bb1 ], [ %{{.*}}, %bb2 ]
+; CHECK: %[[RETVAL:.*]] = phi i32* [ %{{.*}}, %bb1 ], [ %{{.*}}, %bb2 ]
+; CHECK: tail call i8* @objc_autoreleaseReturnValue(i8* %[[PHIVAL]])
+; CHECK: ret i32* %[[RETVAL]]
+
+define i32* @test27(i1 %cond) {
+entry:
+ br i1 %cond, label %bb1, label %bb2
+bb1:
+ %v0 = call i32* @func27(i32 1)
+ %v1 = bitcast i32* %v0 to i8*
+ br label %bb3
+bb2:
+ %v2 = call i32* @func27(i32 2)
+ %v3 = bitcast i32* %v2 to i8*
+ br label %bb3
+bb3:
+ %phival = phi i8* [ %v1, %bb1 ], [ %v3, %bb2 ]
+ %retval = phi i32* [ %v0, %bb1 ], [ %v2, %bb2 ]
+ %v4 = tail call i8* @objc_autoreleaseReturnValue(i8* %phival)
+ ret i32* %retval
+}
+
!0 = !{}
; CHECK: attributes [[NUW]] = { nounwind }