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add a check for SC_LARGE_MAXCLASS

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If we assume SC_LARGE_MAXCLASS will always fit in a SSIZE_T, then we can
optimize some checks by unconditional subtraction, and then checking flags
only, without a compare statement in x86.
This commit is contained in:
Dave Watson 2018-10-09 11:16:19 -07:00
parent 0ac524308d
commit d1a861fa80
1 changed files with 9 additions and 0 deletions
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9
src/sc.c
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@ -244,6 +244,15 @@ size_classes(
assert(sc_data->large_minclass == SC_LARGE_MINCLASS); assert(sc_data->large_minclass == SC_LARGE_MINCLASS);
assert(sc_data->lg_large_minclass == SC_LG_LARGE_MINCLASS); assert(sc_data->lg_large_minclass == SC_LG_LARGE_MINCLASS);
assert(sc_data->large_maxclass == SC_LARGE_MAXCLASS); assert(sc_data->large_maxclass == SC_LARGE_MAXCLASS);
/*
* In the allocation fastpath, we want to assume that we can
* unconditionally subtract the requested allocation size from
* a ssize_t, and detect passing through 0 correctly. This
* results in optimal generated code. For this to work, the
* maximum allocation size must be less than SSIZE_MAX.
*/
assert(SC_LARGE_MAXCLASS < SSIZE_MAX);
} }
void void