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Re: combine corrupts insns + dumps with insn cost problems

From: Uros Bizjak <ubizjak at gmail dot com>
To: GCC <gcc at gcc dot gnu dot org>
Cc: Rask Ingemann Lambertsen <rask at sygehus dot dk>
Date: Wed, 27 Jun 2007 19:47:33 +0200
Subject: Re: combine corrupts insns + dumps with insn cost problems

Hello!

The clobber of the scratch register has disappeared!

A possible clue as to what sets up the failure is that the second
replacement insn (to replace insn 7)

(set (reg:HI 24)
    (eq:HI (reg:CCZ_C 13 cc)
        (const_int 0 [0x0])))

needs to have a clobber added. It really looks like this:

(set (reg:HI 24)
    (eq:HI (reg:CCZ_C 13 cc)
        (const_int 0 [0x0])))
(clobber (reg:CC 13 cc))

Combine knows how to add clobbers to make insns recognizable. I'm guessing
it accidentally clobbers the original insn in doing so. Where would I look?

Try by tracing through recog_for_combine(), combine.c.

Uros.

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