[PATCH] D54366: RegAllocFast: Add heuristic to detect values not live-out of a block

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.
Herald added a project: LLVM.


================
Comment at: lib/CodeGen/RegAllocFast.cpp:107
+    /// that it is alive accross blocks.
+    BitVector MayLiveAccrossBlocks;
+
----------------
Typo, extra c in Across


================
Comment at: lib/CodeGen/RegAllocFast.cpp:277-278
+  unsigned C = 0;
+  for (const MachineOperand &Use :
+       make_range(std::next(I), MRI->reg_nodbg_end())) {
+    if (Use.getParent()->getParent() != FirstMBB || ++C >= Limit) {
----------------
This is broken because it's skipping the first use. It can also useMRI->reg_nodbg_instructions.

This is also broken for the case where there is a phi/copy when there is a loop back to the same block. This needs to check for whether the use instruction happens before the spilled value def


Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D54366/new/

https://reviews.llvm.org/D54366