This patch enables SimplifyUsingDistributiveLaws() to handle following pattens.

(X >> Z) & (Y >> Z)  -> (X&Y) >> Z  for all shifts.
(X >> Z) | (Y >> Z)  -> (X|Y) >> Z  for all shifts.
(X >> Z) ^ (Y >> Z)  -> (X^Y) >> Z  for all shifts.

These patterns were previously handled separately in visitAnd()/visitOr()/visitXor().

Differential Revision: http://reviews.llvm.org/D4951

llvm-svn: 216443

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

@@ -1351,20 +1351,6 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
       }
     }
 
-  // (X >> Z) & (Y >> Z)  -> (X&Y) >> Z  for all shifts.
-  if (BinaryOperator *SI1 = dyn_cast<BinaryOperator>(Op1)) {
-    if (BinaryOperator *SI0 = dyn_cast<BinaryOperator>(Op0))
-      if (SI0->isShift() && SI0->getOpcode() == SI1->getOpcode() &&
-          SI0->getOperand(1) == SI1->getOperand(1) &&
-          (SI0->hasOneUse() || SI1->hasOneUse())) {
-        Value *NewOp =
-          Builder->CreateAnd(SI0->getOperand(0), SI1->getOperand(0),
-                             SI0->getName());
-        return BinaryOperator::Create(SI1->getOpcode(), NewOp,
-                                      SI1->getOperand(1));
-      }
-  }
-
   {
     Value *X = nullptr;
     bool OpsSwapped = false;
@@ -2227,19 +2213,6 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
   if (match(Op0, m_And(m_Or(m_Specific(Op1), m_Value(C)), m_Value(A))))
     return BinaryOperator::CreateOr(Op1, Builder->CreateAnd(A, C));
 
-  // (X >> Z) | (Y >> Z)  -> (X|Y) >> Z  for all shifts.
-  if (BinaryOperator *SI1 = dyn_cast<BinaryOperator>(Op1)) {
-    if (BinaryOperator *SI0 = dyn_cast<BinaryOperator>(Op0))
-      if (SI0->isShift() && SI0->getOpcode() == SI1->getOpcode() &&
-          SI0->getOperand(1) == SI1->getOperand(1) &&
-          (SI0->hasOneUse() || SI1->hasOneUse())) {
-        Value *NewOp = Builder->CreateOr(SI0->getOperand(0), SI1->getOperand(0),
-                                         SI0->getName());
-        return BinaryOperator::Create(SI1->getOpcode(), NewOp,
-                                      SI1->getOperand(1));
-      }
-  }
-
   // (~A | ~B) == (~(A & B)) - De Morgan's Law
   if (Value *Op0NotVal = dyn_castNotVal(Op0))
     if (Value *Op1NotVal = dyn_castNotVal(Op1))
@@ -2585,18 +2558,6 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
     }
   }
 
-  // (X >> Z) ^ (Y >> Z)  -> (X^Y) >> Z  for all shifts.
-  if (Op0I && Op1I && Op0I->isShift() &&
-      Op0I->getOpcode() == Op1I->getOpcode() &&
-      Op0I->getOperand(1) == Op1I->getOperand(1) &&
-      (Op0I->hasOneUse() || Op1I->hasOneUse())) {
-    Value *NewOp =
-      Builder->CreateXor(Op0I->getOperand(0), Op1I->getOperand(0),
-                         Op0I->getName());
-    return BinaryOperator::Create(Op1I->getOpcode(), NewOp,
-                                  Op1I->getOperand(1));
-  }
-
   if (Op0I && Op1I) {
     Value *A, *B, *C, *D;
     // (A & B)^(A | B) -> A ^ B

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -390,6 +390,25 @@ static bool RightDistributesOverLeft(Instruction::BinaryOps LOp,
                                      Instruction::BinaryOps ROp) {
   if (Instruction::isCommutative(ROp))
     return LeftDistributesOverRight(ROp, LOp);
+
+  switch (LOp) {
+  default:
+    return false;
+  // (X >> Z) & (Y >> Z)  -> (X&Y) >> Z  for all shifts.
+  // (X >> Z) | (Y >> Z)  -> (X|Y) >> Z  for all shifts.
+  // (X >> Z) ^ (Y >> Z)  -> (X^Y) >> Z  for all shifts.
+  case Instruction::And:
+  case Instruction::Or:
+  case Instruction::Xor:
+    switch (ROp) {
+    default:
+      return false;
+    case Instruction::Shl:
+    case Instruction::LShr:
+    case Instruction::AShr:
+      return true;
+    }
+  }
   // TODO: It would be nice to handle division, aka "(X + Y)/Z = X/Z + Y/Z",
   // but this requires knowing that the addition does not overflow and other
   // such subtleties.
@@ -411,26 +430,37 @@ static Value *getIdentityValue(Instruction::BinaryOps OpCode, Value *V) {
 }
 
 /// This function factors binary ops which can be combined using distributive
-/// laws. This also factor SHL as MUL e.g. SHL(X, 2) ==> MUL(X, 4).
+/// laws. This function tries to transform 'Op' based TopLevelOpcode to enable
+/// factorization e.g for ADD(SHL(X , 2), MUL(X, 5)), When this function called
+/// with TopLevelOpcode == Instruction::Add and Op = SHL(X, 2), transforms
+/// SHL(X, 2) to MUL(X, 4) i.e. returns Instruction::Mul with LHS set to 'X' and
+/// RHS to 4.
 static Instruction::BinaryOps
-getBinOpsForFactorization(BinaryOperator *Op, Value *&LHS, Value *&RHS) {
+getBinOpsForFactorization(Instruction::BinaryOps TopLevelOpcode,
+                          BinaryOperator *Op, Value *&LHS, Value *&RHS) {
   if (!Op)
     return Instruction::BinaryOpsEnd;
 
-  if (Op->getOpcode() == Instruction::Shl) {
+  LHS = Op->getOperand(0);
-    if (Constant *CST = dyn_cast<Constant>(Op->getOperand(1))) {
+  RHS = Op->getOperand(1);
-      // The multiplier is really 1 << CST.
+
-      RHS = ConstantExpr::getShl(ConstantInt::get(Op->getType(), 1), CST);
+  switch (TopLevelOpcode) {
-      LHS = Op->getOperand(0);
+  default:
-      return Instruction::Mul;
+    return Op->getOpcode();
+
+  case Instruction::Add:
+  case Instruction::Sub:
+    if (Op->getOpcode() == Instruction::Shl) {
+      if (Constant *CST = dyn_cast<Constant>(Op->getOperand(1))) {
+        // The multiplier is really 1 << CST.
+        RHS = ConstantExpr::getShl(ConstantInt::get(Op->getType(), 1), CST);
+        return Instruction::Mul;
+      }
     }
+    return Op->getOpcode();
   }
 
   // TODO: We can add other conversions e.g. shr => div etc.
-
-  LHS = Op->getOperand(0);
-  RHS = Op->getOperand(1);
-  return Op->getOpcode();
 }
 
 /// This tries to simplify binary operations by factorizing out common terms
@@ -529,8 +559,9 @@ Value *InstCombiner::SimplifyUsingDistributiveLaws(BinaryOperator &I) {
 
   // Factorization.
   Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr;
-  Instruction::BinaryOps LHSOpcode = getBinOpsForFactorization(Op0, A, B);
+  auto TopLevelOpcode = I.getOpcode();
-  Instruction::BinaryOps RHSOpcode = getBinOpsForFactorization(Op1, C, D);
+  auto LHSOpcode = getBinOpsForFactorization(TopLevelOpcode, Op0, A, B);
+  auto RHSOpcode = getBinOpsForFactorization(TopLevelOpcode, Op1, C, D);
 
   // The instruction has the form "(A op' B) op (C op' D)".  Try to factorize
   // a common term.
@@ -552,7 +583,6 @@ Value *InstCombiner::SimplifyUsingDistributiveLaws(BinaryOperator &I) {
     return V;
 
   // Expansion.
-  Instruction::BinaryOps TopLevelOpcode = I.getOpcode();
   if (Op0 && RightDistributesOverLeft(Op0->getOpcode(), TopLevelOpcode)) {
     // The instruction has the form "(A op' B) op C".  See if expanding it out
     // to "(A op C) op' (B op C)" results in simplifications.