From: Paolo Bonzini <bonzini@gnu.org>
To: Andreas Krebbel <Andreas.Krebbel@de.ibm.com>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] lower-subreg: Decompose multiword shifts
Date: Thu, 02 Aug 2007 16:56:00 -0000 [thread overview]
Message-ID: <46B20CB2.7000103@gnu.org> (raw)
In-Reply-To: <20070802153434.GA24953@blc4eb430604175.ibm.com>
> Besides the fact that a shift decomposed into 2 simple move
> instructions can often be merged into other INSNs also the rest of
> lower subreg benefits since more multiword regs can be marked as
> decomposable.
Great! You could investigate changing the code so that the condition
becomes
+ if (INTVAL (shift_count) < BITS_PER_WORD
+ || GET_MODE_BITSIZE (GET_MODE (shift_operand)) != 2 * BITS_PER_WORD)
+ return 0;
(your code has != in the first branch). You can turn the code into a
move+a shift, which simplifies to two moves if INTVAL (shift_count) ==
BITS_PER_WORD, in this case.
Paolo
next prev parent reply other threads:[~2007-08-02 16:56 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-02 15:35 Andreas Krebbel
2007-08-02 16:56 ` Paolo Bonzini [this message]
2007-08-03 16:41 ` Andreas Krebbel
2007-08-03 19:02 ` Paolo Bonzini
2007-08-02 18:52 ` Rask Ingemann Lambertsen
2007-08-02 19:21 ` Andreas Krebbel
2007-08-07 1:41 ` Rask Ingemann Lambertsen
2007-08-07 8:29 ` Andreas Krebbel
2007-08-02 23:16 ` Rask Ingemann Lambertsen
2007-08-03 12:03 ` Michael Matz
2007-08-03 14:34 ` Andreas Krebbel
2007-08-03 15:37 ` Michael Matz
2007-08-07 1:08 ` Ian Lance Taylor
2007-08-07 1:27 ` Ian Lance Taylor
2007-08-07 10:47 ` Andreas Krebbel
2007-08-08 18:40 ` Andreas Tobler
2007-08-09 7:45 ` Andreas Krebbel
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