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Hi Sanjay, I observed some extra register spills when applying the reassociation pass on spec2006 benchmarks and I would like to listen to your advice. For example, function get_new_point_on_quad() of tria_boundary.cc in spec2006/dealII has a sequences of code like this . X=a+b . Y=X+c . Z=Y+d . There are many other instructions between these float adds. The reassociation

This conflict is with many optimizations incl. copy prop, coalescing, hoisting etc. Each could increase register pressure and with similar impact. Attempts to control the register pressure locally (within an optimization pass) tend to get hard to tune and maintain. Would it be a better way to describe eg in metadata how to undo an optimization? Optimizations that attempt to reduce pressure like