Subzero: Improve usability of liveness-related tools.

src/IceRegAlloc.cpp

 //===- subzero/src/IceRegAlloc.cpp - Linear-scan implementation -----------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 150 matching lines @@
   TimerMarker T(TimerStack::TT_initUnhandled, Func);
   FindPreference = false;
   FindOverlap = false;
   SizeT NumVars = 0;
   const VarList &Vars = Func->getVariables();
 
   // Iterate across all instructions and record the begin and end of the live
   // range for each variable that is pre-colored or infinite weight.
   CfgVector<InstNumberT> LRBegin(Vars.size(), Inst::NumberSentinel);
   CfgVector<InstNumberT> LREnd(Vars.size(), Inst::NumberSentinel);
+  llvm::SmallVector<SizeT, 10> DefWithoutUse, UseBeforeDef;

[John, 2015/09/25 23:02:16]

Maybe plural? I.e., DefsWithoutUses

[Jim Stichnoth, 2015/09/25 23:56:01]

Done.

   for (CfgNode *Node : Func->getNodes()) {
     for (Inst &Inst : Node->getInsts()) {
       if (Inst.isDeleted())
         continue;
+      FOREACH_VAR_IN_INST(Var, Inst) {
+        if (Var->getIgnoreLiveness())
+          continue;
+        if (Var->hasReg() || Var->mustHaveReg()) {
+          SizeT VarNum = Var->getIndex();
+          LREnd[VarNum] = Inst.getNumber();
+          if (!Var->getIsArg() && LRBegin[VarNum] == Inst::NumberSentinel)
+            UseBeforeDef.push_back(VarNum);
+        }
+      }
       if (const Variable *Var = Inst.getDest()) {
         if (!Var->getIgnoreLiveness() &&
             (Var->hasReg() || Var->mustHaveReg())) {
           if (LRBegin[Var->getIndex()] == Inst::NumberSentinel) {
             LRBegin[Var->getIndex()] = Inst.getNumber();
             ++NumVars;
           }
         }
       }
-      FOREACH_VAR_IN_INST(Var, Inst) {
-        if (Var->getIgnoreLiveness())
-          continue;
-        if (Var->hasReg() || Var->mustHaveReg())
-          LREnd[Var->getIndex()] = Inst.getNumber();
-      }
     }
   }
 
   Unhandled.reserve(NumVars);
   UnhandledPrecolored.reserve(NumVars);
   for (SizeT i = 0; i < Vars.size(); ++i) {
     Variable *Var = Vars[i];
     if (LRBegin[i] != Inst::NumberSentinel) {
-      assert(LREnd[i] != Inst::NumberSentinel);
+      if (LREnd[i] == Inst::NumberSentinel) {
+        DefWithoutUse.push_back(i);
+        continue;
+      }
       Unhandled.push_back(Var);
       Var->resetLiveRange();
       Var->addLiveRange(LRBegin[i], LREnd[i]);
       Var->untrimLiveRange();
       if (Var->hasReg()) {
         Var->setRegNumTmp(Var->getRegNum());
         Var->setMustHaveReg();
         UnhandledPrecolored.push_back(Var);
       }
       --NumVars;
     }
   }
+  if (!DefWithoutUse.empty() || !UseBeforeDef.empty()) {
+    if (BuildDefs::dump()) {

[John, 2015/09/25 23:02:16]

same thing here

if (DefWithoutUse.empty() && UseBeforeDef.empty())
  return;

if (!dump)
  llvm_report_fatal();

for (...)

for (...)

[Jim Stichnoth, 2015/09/25 23:56:01]

Done.

+      OstreamLocker L(Ctx);
+      Ostream &Str = Ctx->getStrDump();
+      for (SizeT i : DefWithoutUse) {

[John, 2015/09/25 23:02:16]

'i' is weird here. I mostly see single-letter variables when you have an index.
You arguably have an index here, but I would rather it to be named Def

[Jim Stichnoth, 2015/09/25 23:56:01]

Done.

+        Variable *Var = Vars[i];
+        Str << "LR def without use, instruction " << LRBegin[i] << ", variable "
+            << Var->getName(Func) << "\n";
+      }
+      for (SizeT i : UseBeforeDef) {
+        Variable *Var = Vars[i];
+        Str << "LR use before def, instruction " << LREnd[i] << ", variable "
+            << Var->getName(Func) << "\n";
+      }
+    }
+    llvm::report_fatal_error("initForInfOnly: Liveness error");
+  }
   // This isn't actually a fatal condition, but it would be nice to know if we
   // somehow pre-calculated Unhandled's size wrong.
   assert(NumVars == 0);
 
   // Don't build up the list of Kills because we know that no infinite-weight
   // Variable has a live range spanning a call.
   Kills.clear();
 }
 
 void LinearScan::init(RegAllocKind Kind) {
@@ skipping 662 matching lines @@
     Str << "\n";
   }
   Str << "++++++ Inactive:\n";
   for (const Variable *Item : Inactive) {
     dumpLiveRange(Item, Func);
     Str << "\n";
   }
 }
 
 } // end of namespace Ice