When scanning the registers+stack for an SGEN collection, we do not currently scan the XMM (SSE) registers on Linux for Intel.
We do scan FPU registers on Linux for ARM64 ( https://github.com/mono/mono/pull/3764 ). We do not have proof that XMM needs to be scanned on Linux for Intel, however, since Clang has been spotted using XMM registers to accelerate memcpys on Darwin/Intel32 and Darwin/Intel64, and GCC has been spotted using the FPU registers for register spilling on Linux/ARM, it is very likely one or more compilers is using the XMM registers on Linux/Intel and we just haven't caught it yet.
Because this creates high risk for hard-to-spot bugs it should be fixed for C9.
Did this land on C9?
My understanding is Jon Purdy's patch landed in C9, but Jon Purdy's patch was Darwin/Intel and we still need a patch for Linux/Intel. Is this incorrect?
I covered Darwin+Intel. It’s in master, not in mono-4.8.0-branch. The patch should be identical to https://github.com/mono/mono/pull/4134. Shall I make another PR for 4.8?
The original PR has my attempt at fixes for Linux/Windows+Intel. https://github.com/mono/mono/pull/3364
Jon, please do backport Darwin/Intel to 4.8. Thanks.
C9 is now closed. We'll move this bug to the next scheduled milestone, "15.1". We'll continue working on these issues, and will attempt to resolve them ASAP.
Moving back to Ludovic to find someone to work on it.
Adding a note that on x86 linux the ucontext doesn't contain information about xmm regs so we can't scan those registers.