[LLVMbugs] [Bug 13438] X86 slow instruction selector incorrectly folds FS- and GS-relative loads

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=13438

David Chisnall <csdavec at swan.ac.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #2 from David Chisnall <csdavec at swan.ac.uk> 2012-07-24 15:04:35 CDT ---
(In reply to comment #1)
> It's also a correct transform if the value stored at %gs:0 is the address of
> %gs:0.  I don't remember the exact details, but IIRC we do in fact make that
> assumption, at least on some platforms.

That's certainly not a safe assumption in the general case, and breaks on
FreeBSD.  It turns out that ->isELF() was being used to detect whether the
target is Linux.  I've now fixed this in r160687.

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