Dear Maintainer,
after upgrading firefox-esr from 78.15.0esr-1 to 91.4.1esr-1, it can't open
any web page. The tab crashes immediately, with errors like this in dmesg:
traps: Web Content[2691] trap invalid opcode ip:ad209c0d sp:bf87369c error:0 in libxul.so[ac17e000+5844000]

This is a P3 CPU so I guess that SSE2 instructions sneaked in again and this
CPU cannot handle them:
$ cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 11
model name      : Intel(R) Celeron(TM) CPU                1100MHz
stepping        : 1
microcode       : 0x1c
cpu MHz         : 1364.963
cache size      : 256 KB
physical id     : 0
siblings        : 1
core id         : 0
cpu cores       : 1
apicid          : 0
initial apicid  : 0
fdiv_bug        : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov pse36 mmx fxsr sse cpuid
bugs            : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds swapgs itlb_multihit
bogomips        : 2729.92
clflush size    : 32
cache_alignment : 32
address sizes   : 36 bits physical, 32 bits virtual
power management:

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Dear Maintainer,

I have the same issue. I can't open any webpage, all crash instantly.
All of the reports show SIGILL / ILL_ILLOPN, here is one of them:
https://crash-
stats.mozilla.org/report/index/c402dee7-8941-48f1-a6d6-aa7390220107

I also have dmesg full of these lines:
[ 5061.277751] traps: Web Content[2013] trap invalid opcode ip:ad125c0d
sp:bfb40f5c error:0 in libxul.so[ac09a000+5844000]

It violates the i386 baseline by using SSE2 unconditionally, even if the host
CPU doesn't support it (tested on a downclocked Athlon XP).

I suggest that https://wiki.debian.org/SIMDEverywhere might be helpful in
developing a patch, if it isn't just a compiler flag fix.

If this issue/bug is unfixable, the package should depend on package
sse2-support (i386 only).

Workaround: use the epiphany-browser package (GNOME Web). That works without
SSE2.

cat /proc/cpuinfo
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 6
model           : 10
model name      : AMD Athlon(tm)
stepping        : 0
cpu MHz         : 1143.871
cache size      : 512 KB
physical id     : 0
siblings        : 1
core id         : 0
cpu cores       : 1
apicid          : 0
initial apicid  : 0
fdiv_bug        : no
f00f_bug        : no
coma_bug        : no
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 mmx fxsr sse syscall mmxext 3dnowext 3dnow cpuid 3dnowprefetch
vmmcall
bugs            : fxsave_leak sysret_ss_attrs spectre_v1 spectre_v2
spec_store_bypass
bogomips        : 2287.74
clflush size    : 32
cache_alignment : 32
address sizes   : 34 bits physical, 32 bits virtual
power management: ts