[llvm-branch-commits] LiveRangeShrink: Early exit when encountering a code motion barrier. (PR #136806)

[Matt Arsenault via llvm-branch-commits]

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@@ -95,14 +95,24 @@ static MachineInstr *FindDominatedInstruction(MachineInstr &New,
   return Old;
 }
 
+static bool isCodeMotionBarrier(MachineInstr &MI) {
+  return MI.hasUnmodeledSideEffects() && !MI.isPseudoProbe();
+}
+
 /// Builds Instruction to its dominating order number map \p M by traversing
 /// from instruction \p Start.
 static void BuildInstOrderMap(MachineBasicBlock::iterator Start,
                               InstOrderMap &M) {
   M.clear();
   unsigned i = 0;
-  for (MachineInstr &I : make_range(Start, Start->getParent()->end()))
+  bool SawStore = false;
+  for (MachineInstr &I : make_range(Start, Start->getParent()->end())) {
+    if (I.mayStore())
+      SawStore = true;
+    if (!I.isSafeToMove(SawStore) && isCodeMotionBarrier(I))
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arsenm wrote:

The MI.hasUnmodeledSideEffects() is redundant with the isSafeToMove check?

https://github.com/llvm/llvm-project/pull/136806