swift234

Enhance the swift_retainAndReturnThree optimizer to be able to handle the case
when swift_retainAndReturnThree is inlined from a previously optimized function.

The upshot of this is that we compile:

var a : String
func f() -> String {
  return a
}

into:

__T1t3fooFT_NSs6String:
	pushq	%rax
	movq	__T1t1xNSs6String+16(%rip), %rcx
	movq	__T1t1xNSs6String+8(%rip), %rdx
	movq	__T1t1xNSs6String(%rip), %rsi
	movq	%rcx, %rdi
	callq	_swift_retainAndReturnThree
	popq	%rsi
	ret

instead of:

__T1t3fooFT_NSs6String:
	pushq	%r14
	pushq	%rbx
	pushq	%rax
	movq	__T1t1aNSs6String+8(%rip), %r14
	movq	__T1t1aNSs6String(%rip), %rbx
	movq	__T1t1aNSs6String+16(%rip), %rdi
	callq	_swift_retain
	movq	%rax, %rcx
	movq	%rbx, %rax
	movq	%r14, %rdx
	addq	$8, %rsp
	popq	%rbx
	popq	%r14
	ret



Swift SVN r2102