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[X86][AMX] Fix tile config register spill issue.

Authored by LuoYuanke on Jan 5 2021, 5:41 AM.

Description

[X86][AMX] Fix tile config register spill issue.

Previous code build the model that tile config register is the user of
each AMX instruction. There is a problem for the tile config register
spill. When across function, the ldtilecfg instruction may be inserted
on each AMX instruction which use tile config register. This cause all
tile data register clobber.
To fix this issue, we remove the model of tile config register. We
analyze the regmask of call instruction and insert ldtilecfg if there is
any tile data register live across the call. Inserting the sttilecfg
before the call is unneccessary, because the tile config doesn't change
and we can just reload the config.
Besides we also need check tile config register interference. Since we
don't model the config register we should check interference from the
ldtilecfg to each tile data register def.

      ldtilecfg
      /       \
     BB1      BB2
     /         \
    call       BB3
    /           \
%1=tileload   %2=tilezero

We can start from the instruction of each tile def, and backward to
ldtilecfg. If there is any call instruction, and tile data register is
not preserved, we should insert ldtilecfg after the call instruction.

Differential Revision: https://reviews.llvm.org/D94155