[PATCH] Make GVN more iterative

[James Molloy]

Hi all,

GVN currently iterates until it can do no more, then performs PRE. There's a FIXME, saying we should try GVN again if PRE made changes.

This patch changes GVN to do this, motivated by the attached testcase (reduced from SPEC) where GVN currently leaves a redundant load.

The FIXME mentions memory dependence checking, but it looks to me like the memory dependence updating got implemented after the FIXME was written, so it's out of date.

I've tested this for compile time and there are no non-noise regressions (in fact, the geomean was a 5% speedup, interestingly).

What do you think?

Cheers,

James

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