Bug 389700

Valgrind 3.13.0, built from source on Ubuntu 16.04.

Seems similar to bug 339596, except this is from packed signed to packed half precision (the other way around).

vex amd64->IR: unhandled instruction bytes: 0xC4 0xE3 0x7D 0x1D 0xED 0x0 0xC5 0xF9 0xC5 0xF5
vex amd64->IR:   REX=0 REX.W=0 REX.R=0 REX.X=0 REX.B=0
vex amd64->IR:   VEX=1 VEX.L=1 VEX.nVVVV=0x0 ESC=0F3A
vex amd64->IR:   PFX.66=1 PFX.F2=0 PFX.F3=0
==4231== valgrind: Unrecognised instruction at address 0x42a3c5.
==4231==    at 0x42A3C5: _mm256_cvtps_ph (f16cintrin.h:75)
==4231==    by 0x42A3C5: pack_weights_vec8_f16(float*, int*, int*, int, _dims_t*) (compression.c:56)
==4231==    by 0x402FE6: main (test_smiv_csr.cpp:31)
==4231== Your program just tried to execute an instruction that Valgrind
==4231== did not recognise.  There are two possible reasons for this.
==4231== 1. Your program has a bug and erroneously jumped to a non-code
==4231==    location.  If you are running Memcheck and you just saw a
==4231==    warning about a bad jump, it's probably your program's fault.
==4231== 2. The instruction is legitimate but Valgrind doesn't handle it,
==4231==    i.e. it's Valgrind's fault.  If you think this is the case or
==4231==    you are not sure, please let us know and we'll try to fix it.
==4231== Either way, Valgrind will now raise a SIGILL signal which will
==4231== probably kill your program.
==4231==
==4231== Process terminating with default action of signal 4 (SIGILL)
==4231==  Illegal opcode at address 0x42A3C5
==4231==    at 0x42A3C5: _mm256_cvtps_ph (f16cintrin.h:75)
==4231==    by 0x42A3C5: pack_weights_vec8_f16(float*, int*, int*, int, _dims_t*) (compression.c:56)
==4231==    by 0x402FE6: main (test_smiv_csr.cpp:31)