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With every release of a new processor, there are changes to the instructionset the processor supports. For example, Haswell has Advanced Vector Extensions. However, when I run a program on a PC with a Haswell processor I usually run generic AMD64 binaries: the compiler doesn't know these instructions are available. How do these binaries still take advantage of the new instructions added in new architectures?
Martijn
Posted 2014-01-29T11:01:51.463
Reputation: 3 362
While on the one hand that sounds reasonable, it does lead to wonder why these new instructions are added if there is virtually no compiled software available for them. – Martijn – 2014-01-29T11:27:29.450
1There is software that exist but they are mainly single purpose tools – Ramhound – 2014-01-29T12:01:15.233
but really? All those instructions added to different processors since the 8086 in 1978 are not available to anyone downloading a blob compiled for x86? MMX, SSE1 to SSE5, AVX, all that stuff is not available to x86 compatible binaries? I can hardly believe that. – Martijn – 2014-01-29T13:06:55.697
Ugh, I apparently misread your answer, and binaries can be/are compiled to check for extensions? That is basically what my question comes down to. – Martijn – 2014-01-29T13:29:16.043
In addition, once the installed base of hardware supporting a given extension becomes sufficient, the extension can be assumed to be present (similar to OS, disk space, memory, or frequency requirements like "Windows _ or later"). Older hardware will generally produce illegal opcode exceptions (technically, a newer OS on old hardware could emulate such instructions to provide binary compatibility, but since most new instructions are added to improve performance emulation makes less sense [e.g., speech recognition at five words per hour by emulating AVX instructions on a Pentium MMX]). – Paul A. Clayton – 2014-01-29T17:35:11.753