[Bug target/54239] Not able to generate "prefetch" (prefetch read) instruction using -m3dnow or -mprfchw

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54239

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-08-13 13:58:40 UTC ---
But the Intel manual AFAIK doesn't talk about prefetch insn.
So, the -mprfchw switch needs to control solely the prefetchw instruction,
and there might be a different one that controls the prefetch insn.  In
driver-i386.c you could enable -mprfchw vs. ?-mprfch -mpfrchw? based on whether
the CPU is Intel or AMD or something, but if there are CPUs that don't have
both insns, it needs to be enabled independently.  Areg?