From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Paul Mackerras <paulus@ozlabs.org>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] powerpc: rewrite LOAD_REG_IMMEDIATE() as an intelligent macro
Date: Wed, 14 Aug 2019 11:46:41 +0200 [thread overview]
Message-ID: <3d4e757f-84cd-7a48-0b5a-d39c44ea33ea@c-s.fr> (raw)
In-Reply-To: <20190814020803.it7i7mjxyruu4vy3@oak.ozlabs.ibm.com>
Le 14/08/2019 à 04:08, Paul Mackerras a écrit :
> On Tue, Aug 13, 2019 at 09:59:35AM +0000, Christophe Leroy wrote:
>
> [snip]
>
>> +.macro __LOAD_REG_IMMEDIATE r, x
>> + .if \x & ~0xffffffff != 0
>> + __LOAD_REG_IMMEDIATE_32 \r, (\x) >> 32
>> + rldicr \r, \r, 32, 31
>> + .if (\x) & 0xffff0000 != 0
>> + oris \r, \r, (\x)@__AS_ATHIGH
>> + .endif
>> + .if (\x) & 0xffff != 0
>> + oris \r, \r, (\x)@l
>> + .endif
>> + .else
>> + __LOAD_REG_IMMEDIATE_32 \r, \x
>> + .endif
>> +.endm
>
> Doesn't this force all negative constants, even small ones, to use
> the long sequence? For example, __LOAD_REG_IMMEDIATE r3, -1 will
> generate (as far as I can see):
>
> li r3, -1
> rldicr r3, r3, 32, 31
> oris r3, r3, 0xffff
> ori r3, r3, 0xffff
>
> which seems suboptimal.
Ah yes, thanks. And it is also buggy when \x is over 0x80000000 because
lis is a signed ops
I'll send v2
Christophe
next prev parent reply other threads:[~2019-08-14 9:48 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-13 9:59 [PATCH 1/2] powerpc: rewrite LOAD_REG_IMMEDIATE() as an intelligent macro Christophe Leroy
2019-08-13 9:59 ` [PATCH 2/2] powerpc/32: replace LOAD_MSR_KERNEL() by LOAD_REG_IMMEDIATE() Christophe Leroy
2019-08-14 2:08 ` [PATCH 1/2] powerpc: rewrite LOAD_REG_IMMEDIATE() as an intelligent macro Paul Mackerras
2019-08-14 9:46 ` Christophe Leroy [this message]
2019-08-14 20:10 ` Segher Boessenkool
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