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Re: does the instruction combiner regards (foo & 0xff) as a special case?

From: Ian Lance Taylor <ian at airs dot com>
To: ibanez at sunplus dot com
Cc: gcc at gcc dot gnu dot org
Date: 31 Jul 2005 19:56:53 -0700
Subject: Re: does the instruction combiner regards (foo & 0xff) as a special case?
References: <OFB47F2AC8.B497872A-ON48257050.000F5FED-48257050.000F6001@sunplus.com>

ibanez@sunplus.com writes:

> Does the instruction combiner regards (foo & 0xff) as a special case?
> 
> I have two patterns which I expect to match all the
> 
> if(foo & $(constant)) patterns. They are
> 
>   [(set (reg:CC_Z CC_REGNUM)
>         (compare:CC_Z
>               (and:SI (match_operand:SI 0 "register_operand" "")
>                     (match_operand:SI 1 "" ""))
>               (const_int 0)))]
> 
>    [(set (reg:CC_Z CC_REGNUM)
>       (compare:CC_Z (zero_extract:SI
>                     (match_operand:SI 0 "register_operand" "")
>                     (const_int 1)
>                     (match_operand:SI 1 "" ""))
>                    (const_int 0)))]
> 
> But I found they fails to match
> 
> if(foo & 0xff) and if(foo & 0xffff)

Look at the debugging dump before the combine pass to see what you
need to match.

Ian

References:
- does the instruction combiner regards (foo & 0xff) as a special case?
  - From: ibanez

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