Re: [PATCH 1/2] powerpc: rewrite LOAD_REG_IMMEDIATE() as an intelligent macro

[Paul Mackerras]

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.

Paul.