Re: [PATCH v3 3/3] powerpc/64: optimise LOAD_REG_IMMEDIATE_SYM()

[Nicholas Piggin]

Segher Boessenkool's on August 20, 2019 12:24 am:
> On Mon, Aug 19, 2019 at 01:58:12PM +0000, Christophe Leroy wrote:
>> -#define LOAD_REG_IMMEDIATE_SYM(reg,expr)	\
>> -	lis     reg,(expr)@highest;		\
>> -	ori     reg,reg,(expr)@higher;	\
>> -	rldicr  reg,reg,32,31;		\
>> -	oris    reg,reg,(expr)@__AS_ATHIGH;	\
>> -	ori     reg,reg,(expr)@l;
>> +#define LOAD_REG_IMMEDIATE_SYM(reg, tmp, expr)	\
>> +	lis	reg, (expr)@highest;		\
>> +	lis	tmp, (expr)@__AS_ATHIGH;	\
>> +	ori	reg, reg, (expr)@higher;	\
>> +	ori	tmp, reg, (expr)@l;		\
>> +	rldimi	reg, tmp, 32, 0
> 
> That should be
> 
> #define LOAD_REG_IMMEDIATE_SYM(reg, tmp, expr)	\
> 	lis	tmp, (expr)@highest;		\
> 	ori	tmp, tmp, (expr)@higher;	\
> 	lis	reg, (expr)@__AS_ATHIGH;	\
> 	ori	reg, reg, (expr)@l;		\
> 	rldimi	reg, tmp, 32, 0
> 
> (tmp is the high half, reg is the low half, as inputs to that rldimi).

I guess the intention was also to try to fit the independent ops into
the earliest fetch/issue cycle possible.

#define LOAD_REG_IMMEDIATE_SYM(reg, tmp, expr)	\
	lis	tmp, (expr)@highest;		\
	lis	reg, (expr)@__AS_ATHIGH;	\
	ori	tmp, tmp, (expr)@higher;	\
	ori	reg, reg, (expr)@l;		\
	rldimi	reg, tmp, 32, 0

Very cool series though.

Thanks,
Nick