From: Ian Lance Taylor <iant@google.com>
To: He Xiao <xiheasas@gmail.com>
Cc: gcc-help@gcc.gnu.org
Subject: Re: A very odd phenomenon when does -O1
Date: Fri, 05 Mar 2010 15:54:00 -0000 [thread overview]
Message-ID: <mcrpr3ig3xs.fsf@dhcp-172-17-9-151.mtv.corp.google.com> (raw)
In-Reply-To: <910910031003040619uc54c06fua0f6936ae99420a7@mail.gmail.com> (He Xiao's message of "Thu\, 4 Mar 2010 22\:19\:34 +0800")
He Xiao <xiheasas@gmail.com> writes:
> after GREG, the insn becomes
>
> (insn 91 40 45 5 (set (reg:SI 27 r27 [orig:54+-2 ] [54])
> (high:SI (const_int 24930 [0x6162]))) 4 {arch_movsi} (nil)
> (nil)
>
> which matches "arch_movsi" pattern, and thus 0x6162 is not qualified
> for arch_move_operand, the final output is as follow:
Why does this match arch_movsi? arch_movsi does not have HIGH in the
pattern. Does your arch_move_operand predicate accept HIGH? If so,
why?
Note that there are a number of examples of backends with similar
restrictions. E.g., mips. They usually do not use HIGH with
CONST_INT; they use HIGH with SYMBOL_REF. For CONST_INT they split up
the value in the movsi define_expand, and then use predicates to
prevent the real insns from matching anything which the architecture
does not support.
Ian
prev parent reply other threads:[~2010-03-05 15:54 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-04 14:19 He Xiao
2010-03-05 15:54 ` Ian Lance Taylor [this message]
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