Bug 421887 – unsupported instruction sets detected as working

• Product: Gentoo Linux
• Status: RESOLVED INVALID

[Description Radu Benea 2012-06-19 08:12:08 UTC]

I suppose this is somehow related to gcc but I don't really know where it's coming from... with just -march=native or -march=athlon64-sse3 the following happens with a multitude of packages

my current temporary solution was to add -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -mno-sse4 -mno-avx to CFLAGS and CXXFLAGS but adding -mno-newinstructionset each time one pops up is not a real solution

detected by qt build system... but glibc, mplayer and other stuff do the same

MMX/3DNOW/SSE/SSE2/SSE3. yes/yes/yes/yes/yes
SSSE3/SSE4.1/SSE4.2..... yes/yes/yes
AVX..................... yes

my /proc/cpuinfo

processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 107
model name      : AMD Athlon(tm) X2 Dual Core Processor BE-2300
stepping        : 2
cpu MHz         : 1900.000
cache size      : 512 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 2
apicid          : 0
initial apicid  : 0
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
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 rdtscp lm 3dnowext 3dnow rep_good nopl extd_apicid pni cx16 lahf_lm cmp_legacy svm extapic cr8_legacy 3dnowprefetch lbrv
bogomips        : 3817.49
TLB size        : 1024 4K pages
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management: ts fid vid ttp tm stc 100mhzsteps

processor       : 1
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 107
model name      : AMD Athlon(tm) X2 Dual Core Processor BE-2300
stepping        : 2
cpu MHz         : 1900.000
cache size      : 512 KB
physical id     : 0
siblings        : 2
core id         : 1                                                                                                                                                                                                                          
cpu cores       : 2                                                                                                                                                                                                                          
apicid          : 1                                                                                                                                                                                                                          
initial apicid  : 1                                                                                                                                                                                                                          
fpu             : yes                                                                                                                                                                                                                        
fpu_exception   : yes                                                                                                                                                                                                                        
cpuid level     : 1                                                                                                                                                                                                                          
wp              : yes                                                                                                                                                                                                                        
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 rdtscp lm 3dnowext 3dnow rep_good nopl extd_apicid pni cx16 lahf_lm cmp_legacy svm extapic cr8_legacy 3dnowprefetch lbrv                                                                                                                                                                                                                
bogomips        : 3817.49                                                                                                                                                                                                                    
TLB size        : 1024 4K pages                                                                                                                                                                                                              
clflush size    : 64                                                                                                                                                                                                                         
cache_alignment : 64                                                                                                                                                                                                                         
address sizes   : 40 bits physical, 48 bits virtual                                                                                                                                                                                          
power management: ts fid vid ttp tm stc 100mhzsteps

[Comment 1 Diego Elio Pettenò (RETIRED) 2012-06-19 12:21:31 UTC]

This is not really a bug. What this tell the software is that they _can_ compile those instructions. Whether they can use it or not it's a different point altogether. In general, software is designed to check at runtime which instruction sets are available — so for instance your glibc has an AVX version of strcasecmp, but will use it only if your CPU is capable of that.