lkml.org 
[lkml]   [2019]   [Aug]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 1/2] powerpc: rewrite LOAD_REG_IMMEDIATE() as an intelligent macro
From
Date


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

\
 
 \ /
  Last update: 2019-08-14 11:47    [W:0.035 / U:1.812 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site