SSSE3 fails when built with GCC 4.6.3

[Ineiev]

As of 9b651fb632f369, on one of my machines tests/basic fails like

AES-128 test decryption failed.
basic: pass 0, algo 7, mode 1, gcry_cipher_setkey failed: Selftest failed
basic: pass 0, algo 7, mode 2, gcry_cipher_setkey failed: Selftest failed
...
basic: cipher-ocb, gcry_cipher_setkey failed (large, algo 7): Selftest failed
basic: cipher-ocb, gcry_cipher_setkey failed (large, algo 7): Selftest failed
basic: stopped after 50 errors.

It seems related to SSSE3 because when I
#undef HAVE_GCC_INLINE_ASM_SSSE3
in config.h, the test succeeds; it also succeeds when compiled without
optimization (CFLAGS=-g2).

$ gcc --version
gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3
...

(When built with gcc 6.2.0, it passes the test.)

$ uname -srvmpio
Linux 3.2.0-118-generic #1trisquel1 SMP Tue Dec 6 16:49:50 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

$ cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 23
model name      : Intel(R) Core(TM)2 Duo CPU     E7400  @ 2.80GHz
stepping        : 10
microcode       : 0xa07
cpu MHz         : 1603.000
cache size      : 3072 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 2
apicid          : 0
initial apicid  : 0
fpu             : yes
fpu_exception   : yes
cpuid level     : 13
wp              : yes
flags           : 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 pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm dtherm tpr_shadow vnmi flexpriority
...
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