Re: [PATCH v4 1/3] powerpc: rewrite LOAD_REG_IMMEDIATE() as an intelligent macro

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 <redacted>

Series applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/c691b4b83b6a348f7b9d13c36916e73c2e1d85e4

cheers