[lra, committed] Fix PR 69447

[Richard Henderson <rth at redhat dot com>]

This PR appears to be related to PR 66424, which Vlad fixed back in September,
but different in that the insn being rematerialized used the entire DImode
pseudo instead of an SImode subreg of a DImode pseudo.

The effect was the same, however, in that it lengthened the lifetime of one
half of the double-word pseudo, causing it to conflict with the coloring set up
by IRA.

While this solves the problem by refusing to remat any double-word pseudo that
has ever had one of its subreg taken, a more complete solution is to also sync
IRA and LRA so that both of them track lifetimes of subregs.  Not for now,
obviously.

Tested on x86_64, i686, and armv7hf-linux.
Approved by Vlad in the PR.


r~

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