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Re: Unexpected behaviour when catching SIGFPE on FPU-less system

To: Shane McDonald <>
Subject: Re: Unexpected behaviour when catching SIGFPE on FPU-less system
From: "Kevin D. Kissell" <>
Date: Tue, 04 May 2010 09:13:18 -0700
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Shane McDonald wrote:
> In the following chunk of code from cp1emu.c:
> value gets set to an initial value of 0x400, and ctx->fcr31
> comes in with an initial value of 0x8420.
> By the time we hit the if statement around the return SIGFPE, ctx->fcr31
> has been set to 0x8400, not the 0x400 I implied.
Ah, well that would rather change things, and you *would* get an
exception there.  As written, the code doesn't seem to allow the pending
exception (.._X) bits to be cleared by the CTC.
> Nevertheless, that's not the problem.  
Maybe it is.  I don't have my MIPS specs handy anymore, but just what is
supposed to clear a pending exception bit in a real FPU?
> You've given me some good pointers
> for where to begin searching for the problem.
> If anyone out there has a verification suite they can run on the emulator,
> that would be much appreciated!
What we used to use was what I *thought* was an old public domain
program whose name was an English word that had something to do with
being exacting.  Googling with obvious keywords didn't turn it up.


          Kevin K.

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