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Re: [Qemu-devel] [5592] target-ppc: optimize popcntb
From: |
Laurent Desnogues |
Subject: |
Re: [Qemu-devel] [5592] target-ppc: optimize popcntb |
Date: |
Sat, 1 Nov 2008 13:29:06 +0100 |
On Sat, Nov 1, 2008 at 1:54 AM, Aurelien Jarno <address@hidden> wrote:
> Revision: 5592
> http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=5592
[...]
> Modified: trunk/target-ppc/op_helper.c
> ===================================================================
> --- trunk/target-ppc/op_helper.c 2008-11-01 00:54:23 UTC (rev 5591)
> +++ trunk/target-ppc/op_helper.c 2008-11-01 00:54:33 UTC (rev 5592)
> @@ -222,25 +222,19 @@
>
> target_ulong helper_popcntb (target_ulong val)
> {
> - uint32_t ret;
> - int i;
> -
> - ret = 0;
> - for (i = 0; i < 32; i += 8)
> - ret |= ctpop8((val >> i) & 0xFF) << i;
> - return ret;
> + val = (val & 0x55555555) + ((val >> 1) & 0x55555555);
> + val = (val & 0x33333333) + ((val >> 2) & 0x33333333);
> + val = (val & 0x0f0f0f0f) + ((val >> 4) & 0x0f0f0f0f);
> + return val;
> }
>
> #if defined(TARGET_PPC64)
> target_ulong helper_popcntb_64 (target_ulong val)
> {
> - uint64_t ret;
> - int i;
> -
> - ret = 0;
> - for (i = 0; i < 64; i += 8)
> - ret |= ctpop8((val >> i) & 0xFF) << i;
> - return ret;
> + val = (val & 0x5555555555555555ULL) + ((val >> 1) &
> 0x5555555555555555ULL);
> + val = (val & 0x3333333333333333ULL) + ((val >> 2) &
> 0x3333333333333333ULL);
> + val = (val & 0x0f0f0f0f0f0f0f0fULL) + ((val >> 4) &
> 0x0f0f0f0f0f0f0f0fULL);
> + return val;
> }
> #endif
Wouldn't it make sense to use builtin's as is done in host-utils.h?
Laurent
- Re: [Qemu-devel] [5592] target-ppc: optimize popcntb,
Laurent Desnogues <=