738e4de01
Denys Vlasenko
2010-10-24
Subject
English fixes to docs/smallint.txt
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docs/smallint.txt+5 -3
| @@ -8,14 +8,15 @@ | |
| I think that this optimization is wrong. | |
| index_in_str_array returns int. At best, compiler will use it as-is. | |
| - | At worst, compiler will try to make sure that it is properly casted |
| + | At worst, compiler will try to make sure that it is properly cast |
| into a byte, which probably results in "n = n & 0xff" on many architectures. | |
| You save nothing on space here because i is not stored on-stack, | |
| - | gcc will keep it in register. And even it is *is* stored, |
| + | gcc will keep it in register. And even if it *is* stored, |
| it is *stack* storage, which is cheap (unlike data/bss). | |
| small[u]ints are useful _mostly_ for: | |
| + | |
| (a) flag variables | |
| (a1) global flag variables - make data/bss smaller | |
| (a2) local flag variables - "a = 5", "a |= 0x40" are smaller | |
| @@ -26,10 +27,11 @@ small[u]ints are useful _mostly_ for: | |
| movl $0x0,(%eax) is "c7 00 00 00 00 00" | |
| movb $0x0,(%eax) is "c6 00 00" | |
| (b) small integer structure members, when you have many such | |
| - | structures allocated, |
| + | structures allocated, |
| or when these are global objects of this structure type | |
| small[u]ints are *NOT* useful for: | |
| + | |
| (a) function parameters and return values - | |
| they are pushed on-stack or stored in registers, bytes here are *harder* | |
| to deal with than ints | |