[llvm] [MachineLICM] Only mark live-ins as non-invariant if defined in loop (PR #191755)

[Yuyang Zhang via llvm-commits]

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@@ -596,20 +596,37 @@ void MachineLICMImpl::HoistRegionPostRA(MachineLoop *CurLoop) {
   SmallVector<CandidateInfo, 32> Candidates;
   SmallDenseSet<int> StoredFIs;
 
-  // Walk the entire region, count number of defs for each register, and
-  // collect potential LICM candidates.
+  // First pass: collect all register units defined within the loop.
+  BitVector LoopRUDefs(NumRegUnits);
+  for (MachineBasicBlock *BB : CurLoop->getBlocks()) {
+    for (MachineInstr &MI : *BB) {
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yuyzhang512 wrote:

Done — factored the def collection into `addRegUnitDefs`.

https://github.com/llvm/llvm-project/pull/191755