Re: conditional exec verify_live problem after scheduling

[Richard Earnshaw <rearnsha at arm dot com>]

> On Wed, 10 Jan 2001, Richard Earnshaw wrote:
> 
> >
> > I've come across the following problem which I think is probably related
> > to your recent conditional-execution scheduling changes (though it may be
> > just uncovering an underlying problem from before).  The problem is in
> > newlib/libm/common/s_modf.c when compiling arm-elf and -mhard-float.
> [...]
> > Now with the first sequence, the compiler thinks that r4 is live at the
> > start of the block; with the second it doesn't.  Now I believe that in
> > both cases r4 should be dead (since a DFmode set of r3 touches both r3 and
> > r4 in the EQ arm, and r4 is explicitly set in the NE arm), but the
> > question is why has the schedule changed the liveness detection?  Are we
> > somehow not handling multi-register sets correctly?
> 
> It ought to handle them correctly.  Are the starting conditions identical
> in both cases?  The bitmaps at the end of the block and at the start of
> all successor blocks must be identical before and after scheduling.
> 
> 
> Bernd
> 

Yes,  After the ce2 pass the regs at the end of the block were
;; End of basic block 2, registers live:
 4 [r4] 5 [r5] 6 [r6] 7 [r7] 8 [r8] 13 [sp] 14 [lr] 16 [f0]

and after sched2
;; End of basic block 2, registers live:
 4 [r4] 5 [r5] 6 [r6] 7 [r7] 8 [r8] 13 [sp] 14 [lr] 16 [f0]

Unfortunately I'm stuck at the moment, RTH's patch for sched-deps speedup 
has revealed a bug in the ARM md file; and trying to fix it has revealed 
problems with genrecog.  So just at the moment I can't even build a 
partially functional compiler.

R.