[PATCH] D98766: [RegAlloc] Fix "ran out of regs" with uses in statepoint

[Serguei Katkov via Phabricator via llvm-commits]

skatkov created this revision.
skatkov added reviewers: reames, dantrushin, greened, qcolombet, dsanders.
Herald added subscribers: pengfei, hiraditya.
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Herald added a project: LLVM.

Statepoint instruction is known to have a variable and big number of operands.
It is possible that Register Allocator will split live intervals in the way that all
physical registers are occupied by "zero-length" live intervals which are marked
as not-spillable.
While intervals are marked as not-spillable in the moment of creation when they are
really zero-length it is possible that in future as part of re-materialization there will
need a physical register.
As all physical registers are assigned to not-spillable intervals there is not avaialbe
registers and RA reports an error.

The idea of the fix is avoid marking tiny live intervals where there is a use in statepoint
instruction in var args section. Such interval may be perfectly spilled and folded to
operand of statepoint.


https://reviews.llvm.org/D98766

Files:
  llvm/include/llvm/CodeGen/CalcSpillWeights.h
  llvm/lib/CodeGen/CalcSpillWeights.cpp
  llvm/test/CodeGen/X86/statepoint-ra.ll

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