xHOST equals what?

xHOST equals what?

hi all,

i would like to verify what the highest optimisation level is that compiling with -xHOST uses (icc 11).

is there any way to check this?

i'm asking because i'm building code on SL5.2 (which is a RHEL5 clone) and /proc/cpuinfo doesn't display (i think) all sse cpabilities. the cpu i'm running on is a xeon L5420 (which should support up to SSE4.1). flags reported are "fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall lm constant_tsc pni monitor ds_cpl vmx est tm2 cx16 xtpr lahf_lm".
although i'm quite sure that icc doesn't rely on whatever the OS thinks the cpu is capable of, i'd like to verifiy this ;)

many thanks,


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For more complete information about compiler optimizations, see our Optimization Notice.

Not sure I understand you. Do you want to check that xHOST is the same as -xSSE4.1 on your platform? You could turn on -S and compare some asm files.

yes, that's what i'd like to know.

i'll see how far i can et with the assembler.

btw, does xSSE4.1 include all availble lower code toptimisations (ie is xSSE4.1 the same as xSSE2,SSE3,SSE4.1)?
and is there any difference with -msse4.1?

thanks a lot,


-xSSE4.1 takes advantage of all the previous instruction sets. It generates much the same code as -xSSE3 and -xSSSE3, except where there is opportunity to use newer instructions.
According to my -S test with -xsse4.1, -msse4.1, and -msse4, all generate the same code. -msse4 is needed for compatibility with gcc; I don't know why you would use -msse4.1.

-xHost will cause icc/icpc or icl to check the cpu information and find the highest level of extended instructions support to use. It does not depend on the OS setting.

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