[PATCH] teach emit_store_flag to use clz/ctz

[Richard Henderson]

On 05/03/2012 03:23 AM, Paolo Bonzini wrote:
> - ctzsi4 expands to bitrev + clz:SI, so it will return 32 too. ctz:SI
> will never appear at all in the RTX stream, so you can define its value
> at zero to be whatever you want.  Hence the correct valid of
> CTZ_DEFINED_VALUE_AT_ZERO is also 2.

That's for armv6.  For armv5 we don't have bitrev, so we use 31-clz,
which yields a value at 0 of -1.  Here I think it's best to mirror
the rs6000 port in that CLZ_DVAZ == 2, but CTZ_DVAZ == 1.

> Similar reasoning applies basically everywhere.

One really needs to examine these closely, one by one.


r~