[IPSCCP] Use constant range information for comparisons of parameters.

For comparisons with parameters, we can use the ParamState lattice
elements which also provide constant range information. This improves
the code for PR33253 further and gets us closer to use
ValueLatticeElement for all values.

Also, as we are using the range information in the solver directly, we
do not need tryToReplaceWithConstantRange afterwards anymore.

Reviewers: dberlin, mssimpso, davide, efriedma

Reviewed By: mssimpso

Differential Revision: https://reviews.llvm.org/D43762

llvm-svn: 328307

1 files changed, 17 insertions, 50 deletions

diff --git a/llvm/lib/Transforms/Scalar/SCCP.cpp b/llvm/lib/Transforms/Scalar/SCCP.cpp
index 5a6697fd9fe..d6fbbce23a3 100644
--- a/llvm/lib/Transforms/Scalar/SCCP.cpp
+++ b/llvm/lib/Transforms/Scalar/SCCP.cpp
@@ -69,8 +69,6 @@ STATISTIC(NumDeadBlocks , "Number of basic blocks unreachable");
 STATISTIC(IPNumInstRemoved, "Number of instructions removed by IPSCCP");
 STATISTIC(IPNumArgsElimed ,"Number of arguments constant propagated by IPSCCP");
 STATISTIC(IPNumGlobalConst, "Number of globals found to be constant by IPSCCP");
-STATISTIC(IPNumRangeInfoUsed, "Number of times constant range info was used by"
-                              "IPSCCP");
 
 namespace {
 
@@ -1039,15 +1037,26 @@ void SCCPSolver::visitBinaryOperator(Instruction &I) {
 
 // Handle ICmpInst instruction.
 void SCCPSolver::visitCmpInst(CmpInst &I) {
-  LatticeVal V1State = getValueState(I.getOperand(0));
-  LatticeVal V2State = getValueState(I.getOperand(1));
-
   LatticeVal &IV = ValueState[&I];
   if (IV.isOverdefined()) return;
 
-  if (V1State.isConstant() && V2State.isConstant()) {
-    Constant *C = ConstantExpr::getCompare(
-        I.getPredicate(), V1State.getConstant(), V2State.getConstant());
+  Value *Op1 = I.getOperand(0);
+  Value *Op2 = I.getOperand(1);
+
+  // For parameters, use ParamState which includes constant range info if
+  // available.
+  auto V1Param = ParamState.find(Op1);
+  ValueLatticeElement V1State = (V1Param != ParamState.end())
+                                    ? V1Param->second
+                                    : getValueState(Op1).toValueLattice();
+
+  auto V2Param = ParamState.find(Op2);
+  ValueLatticeElement V2State = V2Param != ParamState.end()
+                                    ? V2Param->second
+                                    : getValueState(Op2).toValueLattice();
+
+  Constant *C = V1State.getCompare(I.getPredicate(), I.getType(), V2State);
+  if (C) {
     if (isa<UndefValue>(C))
       return;
     return markConstant(IV, &I, C);
@@ -1616,45 +1625,6 @@ bool SCCPSolver::ResolvedUndefsIn(Function &F) {
   return false;
 }
 
-static bool tryToReplaceWithConstantRange(SCCPSolver &Solver, Value *V) {
-  bool Changed = false;
-
-  // Currently we only use range information for integer values.
-  if (!V->getType()->isIntegerTy())
-    return false;
-
-  const ValueLatticeElement &IV = Solver.getLatticeValueFor(V);
-  if (!IV.isConstantRange())
-    return false;
-
-  for (auto UI = V->uses().begin(), E = V->uses().end(); UI != E;) {
-    const Use &U = *UI++;
-    auto *Icmp = dyn_cast<ICmpInst>(U.getUser());
-    if (!Icmp || !Solver.isBlockExecutable(Icmp->getParent()))
-      continue;
-
-    auto getIcmpLatticeValue = [&](Value *Op) {
-      if (auto *C = dyn_cast<Constant>(Op))
-        return ValueLatticeElement::get(C);
-      return Solver.getLatticeValueFor(Op);
-    };
-
-    ValueLatticeElement A = getIcmpLatticeValue(Icmp->getOperand(0));
-    ValueLatticeElement B = getIcmpLatticeValue(Icmp->getOperand(1));
-
-    Constant *C = A.getCompare(Icmp->getPredicate(), Icmp->getType(), B);
-    if (C) {
-      Icmp->replaceAllUsesWith(C);
-      DEBUG(dbgs() << "Replacing " << *Icmp << " with " << *C
-                   << ", because of range information " << A << " " << B
-                   << "\n");
-      Icmp->eraseFromParent();
-      Changed = true;
-    }
-  }
-  return Changed;
-}
-
 static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V) {
   Constant *Const = nullptr;
   if (V->getType()->isStructTy()) {
@@ -1923,9 +1893,6 @@ bool llvm::runIPSCCP(Module &M, const DataLayout &DL,
           ++IPNumArgsElimed;
           continue;
         }
-
-        if (!AI->use_empty() && tryToReplaceWithConstantRange(Solver, &*AI))
-          ++IPNumRangeInfoUsed;
       }
 
     for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {