[PATCH] D127642: [RISCV] Fixing undefined physical register issue when subreg liveness tracking enabled.

[Fraser Cormack via Phabricator via llvm-commits]

frasercrmck added a comment.

The fix LGTM.

As for the test, I'm wondering: maybe it's good to have a "real-world" test case for this, but couldn't we test it far more simply? As it stands I'm finding it hard to find the actual bug in the test case.

Just to see how small the test case could be, I tried and was able to reproduce the issue with this test:

  ---
  name:            foo
  tracksRegLiveness: true
  stack:
    - { id: 0, name: '', type: spill-slot, offset: 0, size: 32, alignment: 8,
        stack-id: scalable-vector, callee-saved-register: '', callee-saved-restored: true }
  body:   |
    bb.0:
      liveins: $v8m2, $x10, $x11
      PseudoVSPILL2_M2 killed $v8m2_v10m2, killed $x10, killed $x11 :: (store unknown-size into %stack.0, align 8)
      PseudoRET
  ...

Perhaps that's a little too simplistic, but it does show off the issue rather cleanly.



================
Comment at: llvm/test/CodeGen/RISCV/rvv/undef-subreg-range.mir:6
+--- |
+  ; ModuleID = '/scratch1/kitoc/llvm-workspace/llvm-project/llvm/test/CodeGen/RISCV/early-clobber-tied-def-subreg-liveness.ll'
+  source_filename = "/scratch1/kitoc/llvm-workspace/llvm-project/llvm/test/CodeGen/RISCV/early-clobber-tied-def-subreg-liveness.ll"
----------------
Regardless of my comment below, we probably don't need these `ModuleID`s or `source_filename`s?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D127642/new/

https://reviews.llvm.org/D127642