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Re: Paradoxical subreg reload issue
- From: Ian Lance Taylor <iant at google dot com>
- To: Aurelien Buhrig <aurelien dot buhrig dot gcc at gmail dot com>
- Cc: gcc at gcc dot gnu dot org
- Date: Wed, 02 May 2012 07:41:42 -0700
- Subject: Re: Paradoxical subreg reload issue
- References: <4FA12D2A.8080806@gmail.com>
Aurelien Buhrig <aurelien.buhrig.gcc@gmail.com> writes:
> I have an issue (gcc 4.6.3, private bacakend) when reloading operands of
> this insn:
> (set (subreg:SI (reg:QI 21 [ iftmp.1 ]) 0)
> (lshiftrt:SI (reg/v:SI 24 [ w ]) (const_int 31 [0x1f]))
>
> The register 21 is reloaded into
> (reg:QI 0 r0 [orig:21 iftmp.1 ] [21]), which is a HI-wide hw register.
> Since it is a BIG_ENDIAN target, the SI subreg regno is then -1.
>
> Note that word_mode is SImode, whereas the class r0 belongs to is
> HI-wide. I don't know if this matters when reloading.
>
> I have no idea how to debug this, if it is a backend or a reload bug.
> Any idea?
Where did that insn come from? It looks like it really wants to be
(set (reg:QI 21)
(truncate:QI (lshiftrt:SI (reg:SI 24) (const_int 31))))
Ian