Hi, On Fri, 7 Aug 2009, Richard Henderson wrote:
> On 08/07/2009 12:31 PM, Richard Guenther wrote: > > > L.N: > > > exc_ptr.1 = EXC_PTR_EXPR (N); > > > filter.1 = FILTER_EXPR (N); > > > > Does the above have > > virtual operands, thus are there any aliases to whatever EXP_PTR_EXPR > > or FILTER_EXPR load? > > No and no. They will eventually resolve to pseudos generated during > rtl eh expansion. But to avoid silliness at the gimple level I don't > want to allow them to appear at random. Shouldn't it be enough to have EXC_PTR_EXPR/FILTER_EXPR simply be builtin functions with proper attributes. They wouldn't be moved upwards over the EH edge because that would introduce effects after the throwing stmt, and they wouldn't be moved downwards due to use-def relationships on exc_ptr.1/filter.1 in the EH_DISPATCH/RESX uses. > Ideally, the rtl would generate what it needs directly into exc_ptr.1, > but I couldn't figure out any way to do that cleanly. In the end, > generating an extra pseudo for register allocation to coalesce is not > the worst sin I could commit here. > > > Can we CSE FILTER_EXPR (N) and EXC_PTR_EXPR (N)? > > Yes. Which also would just work with builtin functions of proper attributes. Ciao, Michael.
