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Re: IA32: printing FP register variables
- To: Joern Rennecke <amylaar at cygnus dot co dot uk>
- Subject: Re: IA32: printing FP register variables
- From: Jeffrey A Law <law at cygnus dot com>
- Date: Mon, 12 Jul 1999 18:05:45 -0600
- cc: jimb at cygnus dot com, egcs at egcs dot cygnus dot com, gdb at sourceware dot cygnus dot com
- Reply-To: law at cygnus dot com
In message <199907122349.AAA25740@phal.cygnus.co.uk>you write:
> > I'm not sure this is safe either. Consider what happens at basic block
> > boundaries to the regstack. I believe variables location relative to
> > the bottom of the stack can change at a basic block boundary.
>
> Huh? Why that? The FPU doesn't know about the control flow.
Consider two threads of control, each with one variable on the FP stack.
At some point they merge. One variable has to be on the bottom, the other
on the top.
regstack has to track this stuff and emit appropriate code at block boundaries
to move stuff around via copies.
It is also why I believe an LCM based copy propagation algorithm can be used
to improve the code generated by regstack.
jeff