[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
5 files changed