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Re: i686 (PentiumPro) Optimizer Bug
On Mon, Nov 16, 1998 at 10:15:43AM -0600, Robert Lipe wrote:
> I was unable to duplicate this problem with either 1.0.2 (as shipped
> with redhad 5.1) or with a Linux snapshot of egcs-2.92.21.
>
> Interestingly, on 1.1.1, this example emits an opcode the OpenServer
> assembler cannot grok. It seems to choke on:
>
> /usr/tmp/cc2QneXL.s:35:unknown instruction: fcmove
> /usr/tmp/cc2QneXL.s:58:unknown instruction: fcmove
fcmove is a PPro/PII specific instruction: Float conditional move. (There's
also a non-float variant.)
It saves a conditional branch and is therefore used by the optimizer when
compiling w/ march=pentiumpro. Obviously, something's wrong with it ...
--
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| cand.phys. Kurt Garloff C1-O4-101 (Chemiegeb"aude) |
|Lehrstuhl Hochfrequenztechnik (Fakult"at f"ur Elektrotechnik)|
| Universit"at Dortmund D - 44221 Dortmund |
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| garloff@hft.e-technik.uni-dortmund.de |
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