[llvm] [RISC-V] Fix outliner candidate analysis (PR #177126)

[Pengcheng Wang via llvm-commits]

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@@ -3653,6 +3653,22 @@ static bool cannotInsertTailCall(const MachineBasicBlock &MBB) {
 }
 
 static bool analyzeCandidate(outliner::Candidate &C) {
+  // If the expansion register for tail calls is live across the candidate
+  // outlined call site, we cannot outline that candidate as the expansion
+  // would clobber the register.
+  // TODO: Should this check only be done if the outlined sequence returns?
+  const TargetRegisterInfo *TRI = C.getMF()->getSubtarget().getRegisterInfo();
+  const TargetSubtargetInfo &STI = C.getMBB()->getParent()->getSubtarget();
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wangpc-pp wrote:

I think we can just make `analyzeCandidate` a method in `RISCVInstrInfo` so that we can get these `*Info` directly.

https://github.com/llvm/llvm-project/pull/177126