[Bug rtl-optimization/30455] i386 generates unnecessary TEST instructions for arithmetic ops on memory

[ubizjak at gmail dot com]

------- Comment #2 from ubizjak at gmail dot com  2007-01-13 23:43 -------
(In reply to comment #1)

> 
> Combine pass then creates:
> 
> (insn 15 14 16 2 (parallel [
>             (set (reg:SI 58 [ temp.27 ])
>                 (plus:SI (reg/v:SI 62 [ y ])
>                     (mem:SI (reg/v/f:DI 61 [ x ]) [2 S4 A32])))
>             (clobber (reg:CC 17 flags))
>         ]) 207 {*addsi_1} (insn_list:REG_DEP_TRUE 6 (insn_list:REG_DEP_TRUE 7
> (nil)))
>     (expr_list:REG_UNUSED (reg:CC 17 flags)
>         (expr_list:REG_DEAD (reg/v:SI 62 [ y ])
>             (nil))))
> 
> (insn 16 15 40 2 (set (mem:SI (reg/v/f:DI 61 [ x ]) [2 S4 A32])
>         (reg:SI 58 [ temp.27 ])) 40 {*movsi_1} (insn_list:REG_DEP_TRUE 15
> (nil))
>     (expr_list:REG_DEAD (reg/v/f:DI 61 [ x ])
>         (nil)))
> 
> (insn 40 16 41 2 (set (reg:CCGOC 17 flags)
>         (compare:CCGOC (reg:SI 58 [ temp.27 ])
>             (const_int 0 [0x0]))) 3 {*cmpsi_ccno_1} (nil)
>     (expr_list:REG_DEAD (reg:SI 58 [ temp.27 ])
>         (nil)))

Huh, is there any reason why insn 40 does not have any insn links?? It should
link to insn 15 as it uses reg 58. This is also seen in .140r.life1 pass.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30455