[MLGO] Properly Handle Counting Evictions of Candidates

This patch makes it so that onEviction actually gets called when the
model ends up selecting the candidate to evict. Where we were handling
this previously ended up being dead code as we would return earlier with
MCRegister::NoRegister.

Fixes #129841.

Author: boomanaiden154

llvm/lib/CodeGen/MLRegAllocEvictAdvisor.cpp

@@ -860,6 +860,7 @@ MCRegister MLEvictAdvisor::tryFindEvictionCandidate(
   // Regs[CandidatePos].second)
   assert(Regs[CandidatePos].second);
   if (CandidatePos == CandidateVirtRegPos) {
+    onEviction(VirtReg.reg());
     assert(!MustFindEviction);
     return MCRegister::NoRegister;
   }
@@ -869,15 +870,11 @@ MCRegister MLEvictAdvisor::tryFindEvictionCandidate(
   // Update information about how many times the virtual registers being
   // evicted have been evicted so that we can prevent the model from evicting
   // the same ranges continually and eating compile time.
-  if (CandidatePos == CandidateVirtRegPos) {
-    onEviction(VirtReg.reg());
-  } else {
-    for (MCRegUnit Unit : TRI->regunits(Regs[CandidatePos].first)) {
-      LiveIntervalUnion::Query &Q = Matrix->query(VirtReg, Unit);
-      const auto &IFIntervals = Q.interferingVRegs(EvictInterferenceCutoff);
-      for (const LiveInterval *Intf : reverse(IFIntervals)) {
-        onEviction(Intf->reg());
-      }
+  for (MCRegUnit Unit : TRI->regunits(Regs[CandidatePos].first)) {
+    LiveIntervalUnion::Query &Q = Matrix->query(VirtReg, Unit);
+    const auto &IFIntervals = Q.interferingVRegs(EvictInterferenceCutoff);
+    for (const LiveInterval *Intf : reverse(IFIntervals)) {
+      onEviction(Intf->reg());
     }
   }