RFC: [tree ssa] DSE extension

[Joe Buck]

On Thu, Apr 01, 2004 at 11:24:30AM -0800, Dale Johannesen wrote:
> In C++, it seems that an awful lot of unnecessary stack temp memory 
> accesses are making it
> through the optimizers.

Yes, that's a ten-year bug (I first complained about it to the Cygnus
people more than ten years ago).  The tree-ssa people have finally made
some progress in fixing it.

Generally speaking, if the temporary has more than one word, GCC
prematurely commits the temporary to memory, and can't undo that
commitment or clean up the dead stores.

(Progress was made in that ten years, in that temporaries that can go
in registers, or structs of one element that can go into registers,
don't have this dead-store problem).

You'll probably need to wait for GCC 3.5 for something better.