Re: [PATCH v4 1/3] powerpc: rewrite LOAD_REG_IMMEDIATE() as an intelligent macro
From: Michael Ellerman
Date: Wed Aug 28 2019 - 00:24:58 EST
On Tue, 2019-08-20 at 14:34:12 UTC, Christophe Leroy wrote:
> Today LOAD_REG_IMMEDIATE() is a basic #define which loads all
> parts on a value into a register, including the parts that are NUL.
> This means always 2 instructions on PPC32 and always 5 instructions
> on PPC64. And those instructions cannot run in parallele as they are
> updating the same register.
> Ex: LOAD_REG_IMMEDIATE(r1,THREAD_SIZE) in head_64.S results in:
> 3c 20 00 00 lis r1,0
> 60 21 00 00 ori r1,r1,0
> 78 21 07 c6 rldicr r1,r1,32,31
> 64 21 00 00 oris r1,r1,0
> 60 21 40 00 ori r1,r1,16384
> Rewrite LOAD_REG_IMMEDIATE() with GAS macro in order to skip
> the parts that are NUL.
> Rename existing LOAD_REG_IMMEDIATE() as LOAD_REG_IMMEDIATE_SYM()
> and use that one for loading value of symbols which are not known
> at compile time.
> Now LOAD_REG_IMMEDIATE(r1,THREAD_SIZE) in head_64.S results in:
> 38 20 40 00 li r1,16384
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
Series applied to powerpc next, thanks.