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author | Father Chrysostomos <sprout@cpan.org> | 2014-11-28 14:35:40 -0800 |
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committer | Father Chrysostomos <sprout@cpan.org> | 2014-11-30 11:48:42 -0800 |
commit | 662308654967c8d237f3ee651bae9c27cd9feaa2 (patch) | |
tree | 9b54880a1f2ab9af8a41b57e4fd7b8f63b392a2d /pad.h | |
parent | 93fa278758aa71f9c91078585c82898a9c7b8eb6 (diff) | |
download | perl-662308654967c8d237f3ee651bae9c27cd9feaa2.tar.gz |
Minimise the size of padname + string buffer
If we define the struct a little differently, we can begin the string
buffer two bytes into a pointer, rather than pointer-aligned. In case
some platforms can compare pointer-aligned string faster, I added a
#define to allow that. But on 64-bit darwin the speed is identical
either way:
$ time ./miniperl -e 'eval q|my$a;|x50000 . q|eval q<my $A>|'
I ran this three times in each mode, and the average of the user times
differed by less than 1%.
Diffstat (limited to 'pad.h')
-rw-r--r-- | pad.h | 44 |
1 files changed, 32 insertions, 12 deletions
@@ -45,26 +45,46 @@ struct padnamelist { U32 xpadnl_refcnt; }; +/* PERL_PADNAME_MINIMAL uses less memory, but on some platforms + PERL_PADNAME_ALIGNED may be faster, so platform-specific hints can + define one or the other. */ +#if defined(PERL_PADNAME_MINIMAL) && defined (PERL_PADNAME_ALIGNED) +# error PERL_PADNAME_MINIMAL and PERL_PADNAME_ALIGNED are exclusive +#endif + +#if !defined(PERL_PADNAME_MINIMAL) && !defined(PERL_PADNAME_ALIGNED) +# define PERL_PADNAME_ALIGNED +#endif + +#define _PADNAME_BASE \ + char * xpadn_pv; \ + HV * xpadn_ourstash; \ + union { \ + HV * xpadn_typestash; \ + CV * xpadn_protocv; \ + } xpadn_type_u; \ + U32 xpadn_low; \ + U32 xpadn_high; \ + U32 xpadn_refcnt; \ + int xpadn_gen; \ + U8 xpadn_len; \ + U8 xpadn_flags + struct padname { - char * xpadn_pv; - HV * xpadn_ourstash; - union { - HV * xpadn_typestash; - CV * xpadn_protocv; - } xpadn_type_u; - U32 xpadn_low; - U32 xpadn_high; - U32 xpadn_refcnt; - int xpadn_gen; - U8 xpadn_len; - U8 xpadn_flags; + _PADNAME_BASE; }; struct padname_with_str { +#ifdef PERL_PADNAME_MINIMAL + _PADNAME_BASE; +#else struct padname xpadn_padname; +#endif char xpadn_str[1]; }; +#undef _PADNAME_BASE + #define PADNAME_FROM_PV(s) \ ((PADNAME *)((s) - STRUCT_OFFSET(struct padname_with_str, xpadn_str))) |