diff options
Diffstat (limited to 'OpenAL32')
-rw-r--r-- | OpenAL32/Include/alMain.h | 50 |
1 files changed, 29 insertions, 21 deletions
diff --git a/OpenAL32/Include/alMain.h b/OpenAL32/Include/alMain.h index 1cf1e5e2..0cab5a17 100644 --- a/OpenAL32/Include/alMain.h +++ b/OpenAL32/Include/alMain.h @@ -226,36 +226,44 @@ inline size_t RoundUp(size_t value, size_t r) return value - (value%r); } -/* Fast float-to-int conversion. Assumes the FPU is already in round-to-zero - * mode. */ +/* Fast float-to-int conversion. No particular rounding mode is assumed; the + * IEEE-754 default is round-to-nearest with ties-to-even, though an app could + * change it on its own threads. On some systems, a truncating conversion may + * always be the fastest method. + */ inline ALint fastf2i(ALfloat f) { -#if (defined(__i386__) && !defined(__SSE_MATH__)) || (defined(_M_IX86_FP) && (_M_IX86_FP == 0)) -/* If using the x87 instruction set, try to use more efficient float-to-int - * operations. The fistp instruction converts to integer efficiently enough, - * but it isn't IEEE-754-compliant because it uses the current rounding mode - * instead of always truncating -- the compiler will generate costly control - * word changes with it to get correct behavior. If supported, lrintf converts - * to integer using the current rounding mode, i.e. using fistp without control - * word changes (if nothing even better is available). As long as the rounding - * mode is set to round-to-zero ahead of time, and the call gets inlined, this - * works fine. - * - * Other instruction sets, like SSE and ARM, have opcodes that inherently do - * the right thing, and don't suffer from the same excessive performance - * degredation from float-to-int conversions. - */ -#ifdef HAVE_LRINTF - return lrintf(f); -#elif defined(_MSC_VER) && defined(_M_IX86) +#if defined(_MSC_VER) && defined(_M_IX86_FP) ALint i; +#if _M_IX86_FP > 0 + __asm cvtss2si i, f +#else __asm fld f __asm fistp i +#endif return i; + +#elif (defined(__GNUC__) || defined(__clang__)) && (defined(__i386__) || defined(__x86_64__)) + + ALint i; +#ifdef __SSE_MATH__ + __asm__("cvtss2si %1, %0" : "=r"(i) : "x"(f)); #else - return (ALint)f; + __asm__("flds %1\n fistps %0" : "=m"(i) : "m"(f)); #endif + return i; + + /* On GCC when compiling with -fno-math-errno, lrintf can be inlined to + * some simple instructions. Clang does not inline it, always generating a + * libc call, while MSVC's implementation is horribly slow, so always fall + * back to a normal integer conversion for them. + */ +#elif defined(HAVE_LRINTF) && !defined(_MSC_VER) && !defined(__clang__) + + return lrintf(f); + #else + return (ALint)f; #endif } |