Subzero: Initial O2 lowering

src/IceCfg.cpp

 //===- subzero/src/IceCfg.cpp - Control flow graph implementation ---------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the Cfg class, including constant pool
 // management.
 //
 //===----------------------------------------------------------------------===//
 
 #include "IceCfg.h"
 #include "IceCfgNode.h"
 #include "IceDefs.h"
 #include "IceInst.h"
+#include "IceLiveness.h"
 #include "IceOperand.h"
 #include "IceTargetLowering.h"
 
 namespace Ice {
 
 Cfg::Cfg(GlobalContext *Ctx)
     : Ctx(Ctx), FunctionName(""), ReturnType(IceType_void),
       IsInternalLinkage(false), HasError(false), ErrorMessage(""), Entry(NULL),
-      NextInstNumber(1),
+      NextInstNumber(1), Live(NULL),
       Target(TargetLowering::createLowering(Ctx->getTargetArch(), this)),
       CurrentNode(NULL) {}
 
 Cfg::~Cfg() {}
 
 void Cfg::setError(const IceString &Message) {
   HasError = true;
   ErrorMessage = Message;
   Ctx->getStrDump() << "ICE translation error: " << ErrorMessage << "\n";
 }
@@ skipping 17 matching lines @@
 void Cfg::addArg(Variable *Arg) {
   Arg->setIsArg(this);
   Args.push_back(Arg);
 }
 
 // Returns whether the stack frame layout has been computed yet.  This
 // is used for dumping the stack frame location of Variables.
 bool Cfg::hasComputedFrame() const { return getTarget()->hasComputedFrame(); }
 
 void Cfg::translate() {
-  Ostream &Str = Ctx->getStrDump();
   if (hasError())
     return;
 
-  if (Ctx->isVerbose()) {
-    Str << "================ Initial CFG ================\n";
-    dump();
-  }
+  dump("Initial CFG");
 
   Timer T_translate;
   // The set of translation passes and their order are determined by
   // the target.
   getTarget()->translate();
   T_translate.printElapsedUs(getContext(), "translate()");
 
-  if (Ctx->isVerbose()) {
-    Str << "================ Final output ================\n";
-    dump();
-  }
+  dump("Final output");
 }
 
 void Cfg::computePredecessors() {
   for (NodeList::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
     (*I)->computePredecessors();
   }
 }
 
+void Cfg::renumberInstructions() {
+  NextInstNumber = 1;
+  for (NodeList::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
+    (*I)->renumberInstructions();
+  }
+}
+
 // placePhiLoads() must be called before placePhiStores().
 void Cfg::placePhiLoads() {
   for (NodeList::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
     (*I)->placePhiLoads();
   }
 }
 
 // placePhiStores() must be called after placePhiLoads().
 void Cfg::placePhiStores() {
   for (NodeList::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
     (*I)->placePhiStores();
   }
 }
 
 void Cfg::deletePhis() {
   for (NodeList::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
     (*I)->deletePhis();
   }
 }
 
+void Cfg::doAddressOpt() {
+  for (NodeList::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
+    (*I)->doAddressOpt();
+  }
+}
+
 void Cfg::genCode() {
   for (NodeList::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
     (*I)->genCode();
   }
 }
 
 // Compute the stack frame layout.
 void Cfg::genFrame() {
   getTarget()->addProlog(Entry);
   // TODO: Consider folding epilog generation into the final
   // emission/assembly pass to avoid an extra iteration over the node
   // list.  Or keep a separate list of exit nodes.
   for (NodeList::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
     CfgNode *Node = *I;
     if (Node->getHasReturn())
       getTarget()->addEpilog(Node);
   }
 }
 
+// This is a lightweight version of live-range-end calculation.  Marks
+// the last use of only those variables whose definition and uses are
+// completely with a single block.  It is a quick single pass and
+// doesn't need to iterate until convergence.
+void Cfg::livenessLightweight() {
+  for (NodeList::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
+    (*I)->livenessLightweight();
+  }
+}
+
+void Cfg::liveness(LivenessMode Mode) {
+  Live.reset(new Liveness(this, Mode));
+  Live->init();
+  // Initialize with all nodes needing to be processed.
+  llvm::BitVector NeedToProcess(Nodes.size(), true);
+  while (NeedToProcess.any()) {
+    // Iterate in reverse topological order to speed up convergence.
+    for (NodeList::reverse_iterator I = Nodes.rbegin(), E = Nodes.rend();
+         I != E; ++I) {
+      CfgNode *Node = *I;
+      if (NeedToProcess[Node->getIndex()]) {
+        NeedToProcess[Node->getIndex()] = false;
+        bool Changed = Node->liveness(getLiveness());
+        if (Changed) {
+          // If the beginning-of-block liveness changed since the last
+          // iteration, mark all in-edges as needing to be processed.
+          const NodeList &InEdges = Node->getInEdges();
+          for (NodeList::const_iterator I1 = InEdges.begin(),
+                                        E1 = InEdges.end();
+               I1 != E1; ++I1) {
+            CfgNode *Pred = *I1;
+            NeedToProcess[Pred->getIndex()] = true;
+          }
+        }
+      }
+    }
+  }
+  if (Mode == Liveness_Intervals) {
+    // Reset each variable's live range.
+    for (VarList::const_iterator I = Variables.begin(), E = Variables.end();
+         I != E; ++I) {
+      if (Variable *Var = *I)
+        Var->resetLiveRange();
+    }
+  }
+  // Collect timing for just the portion that constructs the live
+  // range intervals based on the end-of-live-range computation, for a
+  // finer breakdown of the cost.
+  Timer T_liveRange;
+  // Make a final pass over instructions to delete dead instructions
+  // and build each Variable's live range.
+  for (NodeList::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I) {
+    (*I)->livenessPostprocess(Mode, getLiveness());
+  }
+  if (Mode == Liveness_Intervals) {
+    // Special treatment for live in-args.  Their liveness needs to
+    // extend beyond the beginning of the function, otherwise an arg
+    // whose only use is in the first instruction will end up having
+    // the trivial live range [1,1) and will *not* interfere with
+    // other arguments.  So if the first instruction of the method is
+    // "r=arg1+arg2", both args may be assigned the same register.
+    for (SizeT I = 0; I < Args.size(); ++I) {
+      Variable *Arg = Args[I];
+      if (!Live->getLiveRange(Arg).isEmpty()) {
+        // Add live range [-1,0) with weight 0.
+        Live->addLiveRange(Arg, -1, 0, 0);
+      }
+      // Do the same for i64 args that may have been lowered into i32
+      // Lo and Hi components.
+      Variable *Lo = Arg->getLo();
+      if (Lo && !Live->getLiveRange(Lo).isEmpty())
+        Live->addLiveRange(Lo, -1, 0, 0);
+      Variable *Hi = Arg->getHi();
+      if (Hi && !Live->getLiveRange(Hi).isEmpty())
+        Live->addLiveRange(Hi, -1, 0, 0);
+    }
+    // Copy Liveness::LiveRanges into individual variables.  TODO:
+    // Remove Variable::LiveRange and redirect to
+    // Liveness::LiveRanges.  TODO: make sure Variable weights
+    // are applied properly.
+    SizeT NumVars = Variables.size();
+    for (SizeT i = 0; i < NumVars; ++i) {
+      Variable *Var = Variables[i];
+      Var->setLiveRange(Live->getLiveRange(Var));
+      if (Var->getWeight().isInf())
+        Var->setLiveRangeInfiniteWeight();
+      setCurrentNode(NULL);

[jvoung (off chromium), 2014/05/30 15:41:31]

Does setCurrentNode(NULL) need to happen for every variable, or is it loop
invariant?

[Jim Stichnoth, 2014/05/30 23:06:18]

Loop invariant, but actually it doesn't need to be here at all because
Cfg::dump() will take care of it.

+    }
+    T_liveRange.printElapsedUs(getContext(), "live range construction");
+    dump();
+  }
+}
+
+// Traverse every Variable of every Inst and verify that it
+// appears within the Variable's computed live range.
+bool Cfg::validateLiveness() const {
+  bool Valid = true;
+  Ostream &Str = Ctx->getStrDump();
+  for (NodeList::const_iterator I1 = Nodes.begin(), E1 = Nodes.end(); I1 != E1;
+       ++I1) {
+    CfgNode *Node = *I1;
+    InstList &Insts = Node->getInsts();
+    for (InstList::const_iterator I2 = Insts.begin(), E2 = Insts.end();
+         I2 != E2; ++I2) {
+      Inst *Inst = *I2;
+      if (Inst->isDeleted())
+        continue;
+      if (llvm::isa<InstFakeKill>(Inst))
+        continue;
+      int32_t InstNumber = Inst->getNumber();
+      Variable *Dest = Inst->getDest();
+      if (Dest) {
+        // TODO: This instruction should actually begin Dest's live
+        // range, so we could probably test that this instruction is
+        // the beginning of some segment of Dest's live range.  But
+        // this wouldn't work with non-SSA temporaries during
+        // lowering.
+        if (!Dest->getLiveRange().containsValue(InstNumber)) {
+          Valid = false;
+          Str << "Liveness error: inst " << Inst->getNumber() << " dest ";
+          Dest->dump(this);
+          Str << " live range " << Dest->getLiveRange() << "\n";
+        }
+      }
+      for (SizeT I = 0; I < Inst->getSrcSize(); ++I) {
+        Operand *Src = Inst->getSrc(I);
+        SizeT NumVars = Src->getNumVars();
+        for (SizeT J = 0; J < NumVars; ++J) {
+          const Variable *Var = Src->getVar(J);
+          if (!Var->getLiveRange().containsValue(InstNumber)) {
+            Valid = false;
+            Str << "Liveness error: inst " << Inst->getNumber() << " var ";
+            Var->dump(this);
+            Str << " live range " << Var->getLiveRange() << "\n";
+          }
+        }
+      }
+    }
+  }
+  return Valid;
+}
+
 // ======================== Dump routines ======================== //
 
 void Cfg::emit() {
   Ostream &Str = Ctx->getStrEmit();
   Timer T_emit;
   if (!Ctx->testAndSetHasEmittedFirstMethod()) {
     // Print a helpful command for assembling the output.
     // TODO: have the Target emit the header
     // TODO: need a per-file emit in addition to per-CFG
     Str << "# $LLVM_BIN_PATH/llvm-mc"
@@ skipping 10 matching lines @@
     Str << "\t.type\t" << MangledName << ",@function\n";
   }
   for (NodeList::const_iterator I = Nodes.begin(), E = Nodes.end(); I != E;
        ++I) {
     (*I)->emit(this);
   }
   Str << "\n";
   T_emit.printElapsedUs(Ctx, "emit()");
 }
 
-void Cfg::dump() {
+// Dumps the IR with an optional introductory message.
+void Cfg::dump(const IceString &Message) {
+  if (!Ctx->isVerbose())
+    return;
   Ostream &Str = Ctx->getStrDump();
+  if (!Message.empty())
+    Str << "================ " << Message << " ================\n";
   setCurrentNode(getEntryNode());
   // Print function name+args
   if (getContext()->isVerbose(IceV_Instructions)) {
     Str << "define ";
     if (getInternal())
       Str << "internal ";
     Str << ReturnType << " @" << getFunctionName() << "(";
     for (SizeT i = 0; i < Args.size(); ++i) {
       if (i > 0)
         Str << ", ";
       Str << Args[i]->getType() << " ";
       Args[i]->dump(this);
     }
     Str << ") {\n";
   }
   setCurrentNode(NULL);
+  if (getContext()->isVerbose(IceV_Liveness)) {
+    // Print summary info about variables
+    for (VarList::const_iterator I = Variables.begin(), E = Variables.end();
+         I != E; ++I) {
+      Variable *Var = *I;
+      Str << "//"
+          << " multiblock=" << Var->isMultiblockLife() << " "
+          << " weight=" << Var->getWeight() << " ";
+      Var->dump(this);
+      Str << " LIVE=" << Var->getLiveRange() << "\n";
+    }
+  }
   // Print each basic block
   for (NodeList::const_iterator I = Nodes.begin(), E = Nodes.end(); I != E;
        ++I) {
     (*I)->dump(this);
   }
   if (getContext()->isVerbose(IceV_Instructions)) {
     Str << "}\n";
   }
 }
 
 } // end of namespace Ice