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From: "olegendo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/53987] [SH] Unnecessary zero-extensions
Date: Tue, 27 Jan 2015 23:08:00 -0000 [thread overview]
Message-ID: <bug-53987-4-Bg3P1bvsRT@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-53987-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53987
--- Comment #11 from Oleg Endo <olegendo at gcc dot gnu.org> ---
(In reply to Oleg Endo from comment #9)
> Another related issue is this example function:
>
> unsigned char h (unsigned char a, int b)
> {
> return (unsigned char)(a + b);
> }
>
> It seems that the fwprop1 pass causes this.
I've tried disabling fwprop and matching of combined insns with hard regs in
sh_legitimate_combined_insn. But it doesn't help in this case. The problem is
that
(insn 8 7 13 2 (set (reg:SI 169)
(plus:SI (reg/v:SI 165 [ a ])
^^^^^^^^
(subreg:SI (reg:QI 168 [ b ]) 0))) sh_tmp.cpp:14 63
{*addsi3_compact}
the reg:SI 165 is zero_extended beforehand and then of course also the
subreg:SI (reg:QI 168) doesn't help it anymore.
If -mrenesas is not specified the example compiles to
mov r5,r0
add r4,r0
rts
extu.b r0,r0 // zero extension of return value mandated by gnu abi
which doesn't have the problem. It's initially expanded with two zero_extend
(one on the function arg + one for the return value) and then combine figures
that the first zero_extend can be eliminated.
next prev parent reply other threads:[~2015-01-27 23:08 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-16 23:50 [Bug target/53987] New: [SH] Unnecessary zero-extension before cmp/eq olegendo at gcc dot gnu.org
2012-08-31 18:14 ` [Bug target/53987] " olegendo at gcc dot gnu.org
2013-10-29 21:58 ` olegendo at gcc dot gnu.org
2013-12-16 19:07 ` olegendo at gcc dot gnu.org
2014-12-17 21:09 ` olegendo at gcc dot gnu.org
2014-12-21 16:54 ` [Bug target/53987] [SH] Unnecessary zero-extensions olegendo at gcc dot gnu.org
2014-12-22 22:27 ` olegendo at gcc dot gnu.org
2014-12-25 1:11 ` olegendo at gcc dot gnu.org
2014-12-30 17:26 ` olegendo at gcc dot gnu.org
2015-01-15 1:37 ` olegendo at gcc dot gnu.org
2015-01-24 13:06 ` olegendo at gcc dot gnu.org
2015-01-27 23:08 ` olegendo at gcc dot gnu.org [this message]
2015-08-01 9:57 ` olegendo at gcc dot gnu.org
2015-09-09 12:15 ` olegendo at gcc dot gnu.org
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