[Bug target/89502] Inefficient access to stack_guard in TCB

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89502

--- Comment #4 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to H.J. Lu from comment #1)
> Ever better, we can use UNSPEC_TP to handle it:
> 
> 	movl	%fs:24, %ecx
> 
> to save a register.

We do, with -O2, but -O1 CSEs the constant into the register for some reason.