[RegAlloc] Constrain rematted regclass to use (#164386)

When rematting we create a new virtual register with the original def's
register class. However the use may have a different register class if
the interval is split, which means we end up with an invalid register
class.

This fixes #164181 by constraining the newly created register to the
use's register class.

The test case is reduced as far as it goes. Because this test requires
us to reach a certain amount of register pressure in certain conditions
I'm not sure if there's an easy way to handwrite this scenario.

0 files changed, 0 insertions, 0 deletions