[FFmpeg-devel] Inline ASM vs. Intrinsics

Måns Rullgård mans
Fri May 11 20:44:53 CEST 2007

Michael Niedermayer <michaelni at gmx.at> writes:

> Hi
> On Fri, May 11, 2007 at 10:22:32AM -0400, Dave Dodge wrote:
>> On Fri, May 11, 2007 at 02:06:11PM +0200, Guillaume POIRIER wrote:
>> > Exactly. I wrongfully assumed that "register" keywork was honnored
>> > with xmm/mm intrinsics, but I was wrong. It's simply ignored by ICC. I
>> > don't know about GCC.
>> According to its documentation gcc also ignores the "register" storage
>> class specifier, except in a few special cases:
>>   - when using asm in a declaration to explicitly specify which register.
>>   - when using -O0.
>>   - when using setjmp on certain rare target platforms.
>> Aside: on IA64 icc supports only intrinsics -- no inline assembly.  On
>> the one hand IA64 assembly is so painful that you'd rarely want to
>> write it manually anyway; but the downside is that the intrinsics
> IA64 is a complete failure with and without intrinsics

IA64 is a complete commercial failure.  Its performance is far better
than any x86-based CPU of the same time period.  The main reason it
failed was lack of good x86 emulation, and people insisting on
continuing to run the same old rubbish non-portable software.

M?ns Rullg?rd
mans at mansr.com

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