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Date: Thu, 2 Nov 2023 08:27:37 -0700
From: Tyler Retzlaff <roretzla@linux.microsoft.com>
To: Morten =?iso-8859-1?Q?Br=F8rup?= <mb@smartsharesystems.com>
Cc: dev@dpdk.org, Bruce Richardson <bruce.richardson@intel.com>,
 Cristian Dumitrescu <cristian.dumitrescu@intel.com>,
 David Hunt <david.hunt@intel.com>,
 Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>,
 Ruifeng Wang <ruifeng.wang@arm.com>,
 Sameh Gobriel <sameh.gobriel@intel.com>,
 Vladimir Medvedkin <vladimir.medvedkin@intel.com>,
 Yipeng Wang <yipeng1.wang@intel.com>
Subject: Re: [PATCH 0/5] use abstracted bit count functions
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On Thu, Nov 02, 2023 at 08:39:04AM +0100, Morten Brørup wrote:
> > From: Tyler Retzlaff [mailto:roretzla@linux.microsoft.com]
> > Sent: Thursday, 2 November 2023 02.05
> > 
> > The first set of conversions missed the long 'l' versions of the
> > builtins that were being used. This series completes the conversion
> > of remaining libraries from __builtin_ctzl and __builtin_clzl.
> 
> NAK to blind search/replace of __builtin_clzl()/clzl().
> 
> Although the size of long is 64 bit on 64 bit architectures, it only 32 bit on 32 bit architectures.
> 
> You need to look at the types these builtins operate on:
> - E.g. in the hash library (patch 3/5) prim_hitmask[i]/sec_hitmask[i] are uint32_t, so rte_ctz32() would be the correct replacement. (I am now asking myself why they were using __builtin_ctzl() instead of __builtin_ctz() here... Probably by mistake.)
> - And if the type is "long", you need conditional compiling (or a wrapper macro) to choose between the 32 bit or 64 bit variants.
> 
> NB: You can blindly replace __builtin_ctzll()/clzll(), if any, by 64 bit functions.

they haven't been blindly replaced. but i would like you to validate my
thinking.

in the case of counting trailing 0s it seems fine if the type is
promoted to 64-bits, in the case of leading i checked the type to make
sure it was already operating on a 64-bit type.

too naive?