[llvm] [MachineOutliner] Preserve regmasks in calls to outlined functions (PR #120940)

[Zhaoxuan Jiang via llvm-commits]

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@@ -1130,6 +1131,12 @@ bool MachineOutliner::outline(
           MachineInstr *MI = &*Iter;
           SmallSet<Register, 2> InstrUseRegs;
           for (MachineOperand &MOP : MI->operands()) {
+            // Collect all regmasks. Merge them in the end.
+            if (MOP.isRegMask()) {
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nocchijiang wrote:

I believe 1-regmask is the most common case and the memory allocation in `MF->allocateRegMask()` should be avoided if possible.

https://github.com/llvm/llvm-project/pull/120940