[MIR-Canon] Fixing non-determinism that was breaking bots (NFC).

An earlier fix of a subtle iterator invalidation bug had uncovered a
nondeterminism that was present in the MultiUsers bag. Problem was that
MultiUsers was being looked up using pointers.

This patch is an NFC change that numbers each multiuser and processes each in
numbered order. This fixes the test failure on netbsd and will likely fix the
green-dragon bot too.

llvm-svn: 363012

llvm/lib/CodeGen/MIRCanonicalizerPass.cpp

@@ -180,6 +180,8 @@ static bool rescheduleCanonically(unsigned &PseudoIdempotentInstCount,
   }
 
   std::map<MachineInstr *, std::vector<MachineInstr *>> MultiUsers;
+  std::map<unsigned, MachineInstr *> MultiUserLookup;
+  unsigned UseToBringDefCloserToCount = 0;
   std::vector<MachineInstr *> PseudoIdempotentInstructions;
   std::vector<unsigned> PhysRegDefs;
   for (auto *II : Instructions) {
@@ -255,6 +257,7 @@ static bool rescheduleCanonically(unsigned &PseudoIdempotentInstCount,
       if (Delta < Distance) {
         Distance = Delta;
         UseToBringDefCloserTo = UseInst;
+        MultiUserLookup[UseToBringDefCloserToCount++] = UseToBringDefCloserTo;
       }
     }
 
@@ -294,19 +297,20 @@ static bool rescheduleCanonically(unsigned &PseudoIdempotentInstCount,
   }
 
   // Sort the defs for users of multiple defs lexographically.
-  for (const auto &E : MultiUsers) {
+  for (const auto &E : MultiUserLookup) {
 
     auto UseI =
         std::find_if(MBB->instr_begin(), MBB->instr_end(),
-                     [&](MachineInstr &MI) -> bool { return &MI == E.first; });
+                     [&](MachineInstr &MI) -> bool { return &MI == E.second; });
 
     if (UseI == MBB->instr_end())
       continue;
 
     LLVM_DEBUG(
         dbgs() << "Rescheduling Multi-Use Instructions Lexographically.";);
     Changed |= rescheduleLexographically(
-        E.second, MBB, [&]() -> MachineBasicBlock::iterator { return UseI; });
+        MultiUsers[E.second], MBB,
+        [&]() -> MachineBasicBlock::iterator { return UseI; });
   }
 
   PseudoIdempotentInstCount = PseudoIdempotentInstructions.size();