diff options
| -rw-r--r-- | OpenAL32/Include/alMain.h | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/OpenAL32/Include/alMain.h b/OpenAL32/Include/alMain.h index 48d8fb4a..78dd01c5 100644 --- a/OpenAL32/Include/alMain.h +++ b/OpenAL32/Include/alMain.h @@ -230,6 +230,21 @@ inline size_t RoundUp(size_t value, size_t r) * mode. */ 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) @@ -240,6 +255,9 @@ inline ALint fastf2i(ALfloat f) #else return (ALint)f; #endif +#else + return (ALint)f; +#endif } |