Re: LOG_LINKS field not set because of gcse1 (or fwprop1) pass

[Paolo Bonzini <paolo dot bonzini at lu dot unisi dot ch>]

Rask Ingemann Lambertsen wrote:
> Today, I had a look at the code I get for __gcc_bcmp() from libgcc2.c. I saw
> a regression from
>
> 	decw	%ax
> 	je	.L2
>
> to
>
> 	movw	%ax,	%cx	; register allocation
> 	decw	%cx
> 	movw	%cx,	%ax	; register allocation
> 	andw	%cx,	%cx	; combine, decw sets condition codes
> 	je	.L2
>
> Given this RTL in a life1 dump, shouldn't there be a LOG_LINKS field in insn
> 101 pointing back to insn 96?

Very shortly speaking, the semantics of how LOG_LINKS are set up are 
very easy to mess up.

But isn't reg 32 dead, because it is only set by insn 98:

(insn 98 96 101 9 (set (reg/v:HI 32 [ size ])
        (reg:HI 43)) 33 {movhi} (insn_list:REG_DEP_TRUE 96 (nil))
    (nil))

after copyprop?

Paolo