[GlobalISel] Add a localizer pass for target to use

Description

[GlobalISel] Add a localizer pass for target to use

This reverts commit r299287 plus clean-ups.

The localizer pass is a helper pass that could be run at O0 in the GISel
pipeline to work around the deficiency of the fast register allocator.
It basically shortens the live-ranges of the constants so that the
allocator does not spill all over the place.

Long term fix would be to make the greedy allocator fast.

Details

Committed
qcolombetMay 26 2017, 6:34 PM
Parents
rL304050: [GVN] Recommit the patch "Add phi-translate support in scalarpre".
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