Go 1.26rc1 test failure

[Stephen Illingworth]

I'm building Go1.26rc1 from source (all.bash)

The testing phase fails with the SIMD test.

##### GOEXPERIMENT=simd go test simd/archsimd/...
ok   simd/archsimd 0.096s
SIGILL: illegal instruction
PC=0x548760 m=2 sigcode=2
instruction bytes: 0xc5 0xfd 0xfd 0xc1 0xc3 0xcc 0xcc 0xcc 0xcc 0xcc 0xcc 0xcc 0xcc 0xcc 0xcc 0xcc

I have an older amd64 CPU (i3-3225) which has limited SIMD instructions.

With regards to testing, all tests following this failure are "skipped due to earlier error"

Should GOEXPERIMENT tests be an automatic part of the test suite? (I hadn't specified any GOEXPERIMENTs)

[peterGo]

Stephen,

Old Intel i3-3220T and new Intel Ultra 7 258V.

---

Intel i3-3220T:

~/go/src$ ./all.bash

##### Test execution environment.
# GOARCH: amd64
# CPU: Intel(R) Core(TM) i3-3220T CPU @ 2.80GHz
# GOOS: linux
# OS Version: Linux 6.8.0-90-generic #91-Ubuntu SMP PREEMPT_DYNAMIC Tue Nov 18 14:14:30 UTC 2025 x86_64

##### GOEXPERIMENT=simd go test simd/archsimd/...

ok   simd/archsimd 0.018s
SIGILL: illegal instruction
PC=0x548760 m=0 sigcode=2

instruction bytes: 0xc5 0xfd 0xfd 0xc1 0xc3 0xcc 0xcc 0xcc 0xcc 0xcc 0xcc 0xcc 0xcc 0xcc 0xcc 0xcc

~/go/src$ go version
go version go1.26-devel_65b71c11d4 Tue Dec 16 13:08:47 2025 -0800 linux/amd64

Intel® Core™ i3-3220T Processor
https://www.intel.com/content/www/us/en/products/sku/65694/intel-core-i33220t-processor-3m-cache-2-80-ghz/specifications.html
Specifications
Advanced Technologies
Instruction Set Extensions
Intel® SSE4.1, Intel® SSE4.2, Intel® AVX

AND

Intel Ultra 7 258V:

~/go/src$ ./all.bash

##### Test execution environment.
# GOARCH: amd64
# CPU: Intel(R) Core(TM) Ultra 7 258V
# GOOS: linux
# OS Version: Linux 6.14.0-37-generic #37~24.04.1-Ubuntu SMP PREEMPT_DYNAMIC Thu Nov 20 10:25:38 UTC 2 x86_64

##### GOEXPERIMENT=simd go test simd/archsimd/...

ok   simd/archsimd 0.006s
SIGILL: illegal instruction
PC=0x57ba1c m=7 sigcode=2
instruction bytes: 0x62 0xf2 0x75 0x8 0x50 0xd0 0x90 0x90 0x90 0xc5 0xfa 0x7f 0x54 0x24 0x60 0x31

~/go/src$ go version
go version go1.26-devel_65b71c11d4 Tue Dec 16 13:08:47 2025 -0800 linux/amd64

Intel® Core™ Ultra 7 Processor 258V
https://www.intel.com/content/www/us/en/products/sku/240957/intel-core-ultra-7-processor-258v-12m-cache-up-to-4-80-ghz/specifications.html
Advanced Technologies
Instruction Set Extensions
Intel® SSE4.1, Intel® SSE4.2, Intel® AVX2

Peter