[llvm] [RISCV] Implement tail call optimization in machine outliner (PR #115297)

[Mark Goncharov via llvm-commits]

================
@@ -2961,6 +2990,17 @@ RISCVInstrInfo::getOutliningCandidateInfo(
   for (auto &MI : RepeatedSequenceLocs[0])
     SequenceSize += getInstSizeInBytes(MI);
 
+  if (!cannotInsertTailCall(RepeatedSequenceLocs[0].back())) {
+    // tail function = 8 bytes. Can't be compressed
----------------
mga-sc wrote:

Rewrote it in a more precise form
```cpp
    // tail call = auipc + jalr in the worst case without linker relaxation.
    CallOverhead = 4 + InstrSizeCExt;
```

https://github.com/llvm/llvm-project/pull/115297