[all-commits] [llvm/llvm-project] 08a3c5: [RegAlloc] Scale the spill weight by target factor...

[Pengcheng Wang via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 08a3c532255d2af8722c32a7484a8648ac0ae2f5
      https://github.com/llvm/llvm-project/commit/08a3c532255d2af8722c32a7484a8648ac0ae2f5
  Author: Pengcheng Wang <wangpengcheng.pp at bytedance.com>
  Date:   2025-03-13 (Thu, 13 Mar 2025)

  Changed paths:
    M llvm/include/llvm/CodeGen/TargetRegisterInfo.h
    M llvm/lib/CodeGen/CalcSpillWeights.cpp
    M llvm/lib/CodeGen/TargetRegisterInfo.cpp
    M llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp
    M llvm/lib/Target/RISCV/RISCVRegisterInfo.h
    M llvm/test/CodeGen/RISCV/rvv/abs-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/bitreverse-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/bswap-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/ceil-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/combine-reduce-add-to-vcpop.ll
    M llvm/test/CodeGen/RISCV/rvv/compressstore.ll
    M llvm/test/CodeGen/RISCV/rvv/ctpop-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/cttz-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/expandload.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-bitreverse-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-bswap-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-ceil-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-ctlz-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-ctpop-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-cttz-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-floor-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-fmaximum-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-fminimum-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-int-explodevector.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-interleaved-access.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-nearbyint-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-reduction-fp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-rint-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-round-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-roundeven-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-roundtozero-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-setcc-fp-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-setcc-int-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-trunc-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vcopysign-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vfmax-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vfmin-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vselect-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/floor-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fmaximum-sdnode.ll
    M llvm/test/CodeGen/RISCV/rvv/fmaximum-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fminimum-sdnode.ll
    M llvm/test/CodeGen/RISCV/rvv/fminimum-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fshr-fshl-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/nearbyint-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/rint-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/round-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/roundeven-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/roundtozero-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/setcc-fp-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/setcc-int-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/strided-vpstore.ll
    M llvm/test/CodeGen/RISCV/rvv/vfadd-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfdiv-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfma-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfmadd-constrained-sdnode.ll
    M llvm/test/CodeGen/RISCV/rvv/vfmadd-sdnode.ll
    M llvm/test/CodeGen/RISCV/rvv/vfmax-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfmin-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfmsub-constrained-sdnode.ll
    M llvm/test/CodeGen/RISCV/rvv/vfmul-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfptosi-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfptoui-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfptrunc-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfsub-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfwmacc-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfwnmacc-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfwnmsac-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vpmerge-sdnode.ll
    M llvm/test/CodeGen/RISCV/rvv/vpscatter-sdnode.ll
    M llvm/test/CodeGen/RISCV/rvv/vpstore.ll
    M llvm/test/CodeGen/RISCV/rvv/vselect-fp.ll
    M llvm/test/CodeGen/RISCV/rvv/vselect-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vsitofp-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vtrunc-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vuitofp-vp.ll

  Log Message:
  -----------
  [RegAlloc] Scale the spill weight by target factor (#113675)

Currently, the spill weight is only determined by isDef/isUse and
block frequency. However, for registers with different register
classes, the costs of spilling them are different.

For example, for `LMUL>1` registers (in which, several physical
registers compound a bigger logical register), the costs are larger
than `LMUL=1` case (in which, there is only one physical register).

To solve this problem, a new target hook `getSpillWeightScaleFactor`
is added. Targets can override the default factor (which is `1.0`)
according to the register class.

For RISC-V, the factors are set to the `RegClassWeight` which is
used to track register pressure. The values of `RegClassWeight`
happen to be the number of register units.

I believe all of the targets with compounded registers can benefit
from this change, but only RISC-V is customized in this patch since
it has widely been agreed to do so. The other targets need more
performance data to go further.

Partially fixes #113489.



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