Crash during GC at catch entry about sdk

[rmacnak-google]

/cc @aam

[mraleph]

This is likely related to https://dart-review.googlesource.com/c/sdk/+/269746/comment/f003dd67_7e1c8a4b/

This comment talks about different ParallelMove (BlockEntryInstr::parallel_move_). The one generated here is a normal one after the block entry.

My guess is that the actual bug is here:

void FlowGraphAllocator::AssignSafepoints(Definition* defn, LiveRange* range) {
  for (intptr_t i = safepoints_.length() - 1; i >= 0; i--) {
    Instruction* safepoint_instr = safepoints_[i];
    if (safepoint_instr == defn) {
      // The value is not live until after the definition is fully executed,
      // don't assign the safepoint inside the definition itself to
      // definition's liverange.
      continue;
    }

This check will not correctly work for Parameter "hidden" inside CatchBlockEntry. I wonder why this is not just doing range->Start() < pos maybe it is concerned about presplit liferanges that don't start at their definitions?

[alexmarkov]

@a-siva I have a fix for this almost ready (https://dart-review.googlesource.com/c/sdk/+/363423).