swift234

IRGen: Reenable retain/release optimization of enums with all-refcounted payloads.

r12934 solved the memory corruption issues applying this optimization for String, so now we get a nice branchless implementation of its release operation:

__TwxxOVSs16ContiguousString5Owner:
00000000000828f0        pushq   %rbp
00000000000828f1        movq    %rsp, %rbp
00000000000828f4        movabsq $0x9fffffffffffffff, %rax
00000000000828fe        andq    (%rdi), %rax
0000000000082901        movq    %rax, %rdi
0000000000082904        popq    %rbp
0000000000082905        jmpq    0x881d0

Swift SVN r12937