initial implementation of ValueNumbering interface.

llvm-svn: 3541

llvm/lib/Analysis/ValueNumbering.cpp

@@ -0,0 +1,171 @@
+//===- ValueNumbering.cpp - Value #'ing Implementation ----------*- C++ -*-===//
+//
+// This file implements the non-abstract Value Numbering methods as well as a
+// default implementation for the analysis group.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/BasicValueNumbering.h"
+#include "llvm/Support/InstVisitor.h"
+#include "llvm/BasicBlock.h"
+#include "llvm/Type.h"
+#include "llvm/iMemory.h"
+#include "llvm/InstrTypes.h"
+
+// Register the ValueNumbering interface, providing a nice name to refer to.
+static RegisterAnalysisGroup<ValueNumbering> X("Value Numbering");
+
+/// ValueNumbering destructor: DO NOT move this to the header file for
+/// ValueNumbering or else clients of the ValueNumbering class may not depend on
+/// the ValueNumbering.o file in the current .a file, causing alias analysis
+/// support to not be included in the tool correctly!
+///
+ValueNumbering::~ValueNumbering() {}
+
+//===----------------------------------------------------------------------===//
+// BasicValueNumbering Pass Implementation
+//===----------------------------------------------------------------------===//
+//
+// Because of the way .a files work, the implementation of the
+// BasicValueNumbering class MUST be in the ValueNumbering file itself, or else
+// we run the risk of ValueNumbering being used, but the default implementation
+// not being linked into the tool that uses it.  As such, we register and
+// implement the class here.
+//
+namespace {
+  // Register this pass...
+  RegisterOpt<BasicValueNumbering>
+  X("basicvn", "Basic Value Numbering (default GVN impl)");
+
+  // Declare that we implement the ValueNumbering interface
+  RegisterAnalysisGroup<ValueNumbering, BasicValueNumbering, true> Y;
+}  // End of anonymous namespace
+
+namespace {
+  /// BVNImpl - Implement BasicValueNumbering in terms of a visitor class that
+  /// handles the different types of instructions as appropriate.
+  ///
+  struct BVNImpl : public InstVisitor<BVNImpl> {
+    std::vector<Value*> &RetVals;
+    BVNImpl(std::vector<Value*> &RV) : RetVals(RV) {}
+
+    void visitBinaryOperator(Instruction &I);
+    void visitGetElementPtrInst(GetElementPtrInst &I);
+    void visitCastInst(CastInst &I);
+    void visitShiftInst(ShiftInst &I) { visitBinaryOperator((Instruction&)I); }
+    void visitInstruction(Instruction &) {
+      // Cannot value number calls or terminator instructions...
+    }
+  };
+}
+
+// getEqualNumberNodes - Return nodes with the same value number as the
+// specified Value.  This fills in the argument vector with any equal values.
+//
+void BasicValueNumbering::getEqualNumberNodes(Value *V,
+                                           std::vector<Value*> &RetVals) const {
+  assert(V->getType() != Type::VoidTy &&
+         "Can only value number non-void values!");
+  // We can only handle the case where I is an instruction!
+  if (Instruction *I = dyn_cast<Instruction>(V))
+    BVNImpl(RetVals).visit(I);
+}
+
+void BVNImpl::visitCastInst(CastInst &CI) {
+  Instruction &I = (Instruction&)CI;
+  Value *Op = I.getOperand(0);
+  Function *F = I.getParent()->getParent();
+  
+  for (Value::use_iterator UI = Op->use_begin(), UE = Op->use_end();
+       UI != UE; ++UI)
+    if (Instruction *Other = dyn_cast<Instruction>(*UI))
+      // Check to see if this new cast is not I, but has the same operand...
+      if (Other != &I && Other->getOpcode() == I.getOpcode() &&
+          Other->getOperand(0) == Op &&     // Is the operand the same?
+          // Is it embeded in the same function?  (This could be false if LHS
+          // is a constant or global!)
+          Other->getParent()->getParent() == F &&
+
+          // Check that the types are the same, since this code handles casts...
+          Other->getType() == I.getType()) {
+        
+        // These instructions are identical.  Add to list...
+        RetVals.push_back(Other);
+      }
+}
+
+
+// isIdenticalBinaryInst - Return true if the two binary instructions are
+// identical.
+//
+static inline bool isIdenticalBinaryInst(const Instruction &I1,
+                                         const Instruction *I2) {
+  // Is it embeded in the same function?  (This could be false if LHS
+  // is a constant or global!)
+  if (I1.getOpcode() != I2->getOpcode() ||
+      I1.getParent()->getParent() != I2->getParent()->getParent())
+    return false;
+  
+  // They are identical if both operands are the same!
+  if (I1.getOperand(0) == I2->getOperand(0) &&
+      I1.getOperand(1) == I2->getOperand(1))
+    return true;
+  
+  // If the instruction is commutative and associative, the instruction can
+  // match if the operands are swapped!
+  //
+  if ((I1.getOperand(0) == I2->getOperand(1) &&
+       I1.getOperand(1) == I2->getOperand(0)) &&
+      (I1.getOpcode() == Instruction::Add || 
+       I1.getOpcode() == Instruction::Mul ||
+       I1.getOpcode() == Instruction::And || 
+       I1.getOpcode() == Instruction::Or  ||
+       I1.getOpcode() == Instruction::Xor))
+    return true;
+
+  return false;
+}
+
+void BVNImpl::visitBinaryOperator(Instruction &I) {
+  Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
+  Function *F = I.getParent()->getParent();
+  
+  for (Value::use_iterator UI = LHS->use_begin(), UE = LHS->use_end();
+       UI != UE; ++UI)
+    if (Instruction *Other = dyn_cast<Instruction>(*UI))
+      // Check to see if this new binary operator is not I, but same operand...
+      if (Other != &I && isIdenticalBinaryInst(I, Other)) {        
+        // These instructions are identical.  Handle the situation.
+        RetVals.push_back(Other);
+      }
+}
+
+// IdenticalComplexInst - Return true if the two instructions are the same, by
+// using a brute force comparison.  This is useful for instructions with an
+// arbitrary number of arguments.
+//
+static bool IdenticalComplexInst(const Instruction *I1, const Instruction *I2) {
+  assert(I1->getOpcode() == I2->getOpcode());
+  // Equal if they are in the same function...
+  return I1->getParent()->getParent() == I2->getParent()->getParent() &&
+    // And return the same type...
+    I1->getType() == I2->getType() &&
+    // And have the same number of operands...
+    I1->getNumOperands() == I2->getNumOperands() &&
+    // And all of the operands are equal.
+    std::equal(I1->op_begin(), I1->op_end(), I2->op_begin());
+}
+
+void BVNImpl::visitGetElementPtrInst(GetElementPtrInst &I) {
+  Value *Op = I.getOperand(0);
+  Function *F = I.getParent()->getParent();
+  
+  for (Value::use_iterator UI = Op->use_begin(), UE = Op->use_end();
+       UI != UE; ++UI)
+    if (GetElementPtrInst *Other = dyn_cast<GetElementPtrInst>(*UI))
+      // Check to see if this new getelementptr is not I, but same operand...
+      if (Other != &I && IdenticalComplexInst(&I, Other)) {
+        // These instructions are identical.  Handle the situation.
+        RetVals.push_back(Other);
+      }
+}