SSE2 and SSE4_1 use flags

Project:Linux software
Category:support request
Related pages:#36: CPU - Central Processing Unit :-:-: #10896: Portage USE flags
Tags:CPU, libwebp, SSE, USE flag

I have an update today with changed use flags:

[ebuild   R    ]   media-libs/libwebp-0.5.2  USE="(-neon)" CPU_FLAGS_X86="sse2%* -avx2% -sse4_1%"

cpu_flags_x86_sse2 was previously enabled but is getting disabled:
# equery u libwebp
[ Legend : U - final flag setting for installation]
[        : I - package is installed with flag     ]                                                                      
[ Colors : set, unset                             ]                                                                       
* Found these USE flags for media-libs/libwebp-0.5.2:                                                                        
U I                                                                                                                  
- - abi_x86_32           : 32-bit (x86) libraries
- - cpu_flags_x86_avx2   : Adds support for Advanced Vector Extensions 2 instructions
+ - cpu_flags_x86_sse2   : Use the SSE2 instruction set 
- - cpu_flags_x86_sse4_1 : Enable SSE4.1 instruction support
- - experimental         : Build with -DWEBP_EXPERIMENTAL_FEATURES
+ + gif                  : Add GIF image support
+ + jpeg                 : Add JPEG image support
+ + opengl               : Add support for OpenGL (3D graphics)
+ + png                  : Add support for libpng (PNG images)
- - static-libs          : Build static versions of dynamic libraries as well
- - swap-16bit-csp       : Enable byte swapping for 16 bit colorspace
+ + tiff                 : Add support for the TIFF image format     

my CPU has both:

cat /proc/cpuinfo      
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm 3dnowext 3dnow constant_tsc rep_good nopl nonstop_tsc extd_apicid pni monitor cx16 popcnt lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt hw_pstate npt lbrv svm_lock nrip_save vmmcall

Should I enable them?