[Bug target/29793] TESTW{W,L,Q} rCX + JZ/JE should be replaced by J{,E,R}CXZ when possible

[ubizjak at gmail dot com]

------- Comment #4 from ubizjak at gmail dot com  2007-04-05 12:29 -------
(In reply to comment #2)

> To implement this optimization, some support from assembler is needed. When
> displacement overflows 8bit, assembler should substitute "jecxz" with
> equivalent "test/jmp rel{16,32}" sequence.

Unfortunatelly, test/jmp clobbers flags, and jecxz doesn't. Due to this, and
example in comment #3, we can't reliably generate proposed instructions.


-- 

ubizjak at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |WONTFIX


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29793