in reply to Re^12: Perl 5 Optimizing Compiler, Part 4: LLVM Backend?
in thread Perl 5 Optimizing Compiler, Part 4: LLVM Backend?

Changing FS/GS register is quite dangerous since you will crash if you call anything in (kernel/user/gdi)32 and FS/GS isn't the TIB *.

You're right! I have spent too long living in the x64 world and am forgetting the details of x86.

On x86 it is the ES: segment register that is 'unused'.

On x64, FS: is 'unused'. (GS: points to the TIB/TEB; and ES: (like CS: DS: & SS:) is 'forced to zero'.)

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