[PATCH] ARM: vfp: Fix up exception location in Thumb mode

Russell King - ARM Linux linux at arm.linux.org.uk
Sun Jan 23 10:51:57 EST 2011

On Sun, Jan 16, 2011 at 11:49:21AM +0000, Catalin Marinas wrote:
> On Saturday, 15 January 2011, Russell King - ARM Linux
> <linux at arm.linux.org.uk> wrote:
> > It's a reveq, so I thought we should cover all the instructions with
> > an 'eq' conditional for thumb.
> If the it instruction doesn't cover all instructions, gas generates
> some more its. But in this case, for little endian, the it instruction
> covers more since reveq isn't included and having the beq not last in
> the block I think is unpredictable. If you really want to optimise the
> big endian case not to have an additional it generated by gas, you can
> write ittt so that beq is included with little endian but not with big
> endian. I wouldn't bother much for an extra it anyway.

I think the itttt is correct.  Unless you wish to illustrate why you
think it's wrong by pasting the code and showing why you think the
beq isn't the last instruction...

> >         tst     r3, #PSR_T_BIT
> >         subeq   r4, r2, #4
> > 1:      ldreqt  r0, [r4]
> >         reveq   r0, r0
> >         beq     call_fpe
> You can have the T bit set but the instruction a 32-bit Thumb in which
> case r2 is in the middle of such instruction rather than the next.
> Unless you only refer to the ARM mode, in which case the comment is
> fine.

So?  I'm confused why you're making a mountain out of apparantly

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