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all: use FFDIFFSIGN to resolve possible undefined behavior in comparators

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FFDIFFSIGN was created explicitly for this purpose, since the common
return a - b idiom is unsafe regarding overflow on signed integers. It
optimizes to branchless code on common compilers.

FFDIFFSIGN also has the subjective benefit of being easier to read due
to lack of ternary operators.

Tested with FATE.

Things not covered by this are unsigned integers, for which overflows
are well defined, and also places where overflow is clearly impossible,
e.g an instance where the a - b was being done on 24 bit values.

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Reviewed-by: Clément Bœsch <u@pkh.me>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
This commit is contained in:
Ganesh Ajjanagadde
2015-11-01 10:43:56 -05:00
parent 265f83fd35
commit 92e483f8ed
8 changed files with 13 additions and 21 deletions
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4
cmdutils_opencl.c
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@ -206,7 +206,9 @@ end:
static int compare_ocl_device_desc(const void *a, const void *b)
{
return ((const OpenCLDeviceBenchmark*)a)->runtime - ((const OpenCLDeviceBenchmark*)b)->runtime;
const OpenCLDeviceBenchmark* va = (const OpenCLDeviceBenchmark*)a;
const OpenCLDeviceBenchmark* vb = (const OpenCLDeviceBenchmark*)b;
return FFDIFFSIGN(va->runtime , vb->runtime);
}
int opt_opencl_bench(void *optctx, const char *opt, const char *arg)