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Re: Proposal: immediate strings

From: Paul Eggert
Subject: Re: Proposal: immediate strings
Date: Thu, 31 May 2012 09:34:53 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1

On 05/31/2012 02:28 AM, Dmitry Antipov wrote:
> IIUC this is the only possible layout which: 1) uses bitfields 2) not requires
> __attribute__((packed)) and 3) provides 16-bytes Lisp_String with 10 bytes
> for immediate data on 32-bit and 32-bytes Lisp_String with 22 bytes
> for immediate data on 64-bit.

Ah, sorry, I misunderstood
proposal.  I thought that it grew struct Lisp_String.

Part of my misunderstanding was due to that the code confuses 'unsigned long'
with 'ptrdiff_t'.  The two types need not be the same width.
The code should use 'sizeof (ptrdiff_t)' where it currently
uses 'sizeof (unsigned long)', and we need a BITS_PER_PTRDIFF_T
enum to size the fields correctly.

What are the performance results for this version?

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