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FFI: Make FP to U64 conversions match JIT backend behavior.

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This commit is contained in:
Mike Pall 2018-05-20 12:25:36 +02:00
parent cf7a0540a3
commit f5d424afe8
1 changed files with 13 additions and 5 deletions
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18
src/lj_obj.h
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@ -816,14 +816,22 @@ static LJ_AINLINE int32_t lj_num2bit(lua_Number n)
#define lj_num2int(n) ((int32_t)(n))
#endif
/*
** This must match the JIT backend behavior. In particular for archs
** that don't have a common hardware instruction for this conversion.
** Note that signed FP to unsigned int conversions have an undefined
** result and should never be relied upon in portable FFI code.
** See also: C99 or C11 standard, 6.3.1.4, footnote of (1).
*/
static LJ_AINLINE uint64_t lj_num2u64(lua_Number n)
{
#ifdef _MSC_VER
if (n >= 9223372036854775808.0) /* They think it's a feature. */
return (uint64_t)(int64_t)(n - 18446744073709551616.0);
else
#if LJ_TARGET_X86ORX64 || LJ_TARGET_MIPS
int64_t i = (int64_t)n;
if (i < 0) i = (int64_t)(n - 18446744073709551616.0);
return (uint64_t)i;
#else
return (uint64_t)n;
#endif
return (uint64_t)n;
}
static LJ_AINLINE int32_t numberVint(cTValue *o)