Move some rem transforms out of instcombine and into instsimplify.

This automagically provides a transform noticed by my super-optimizer
as occurring quite often: "rem x, (select cond, x, 1)" -> 0.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130694 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/InstructionSimplify.cpp

@@ -901,6 +901,111 @@ Value *llvm::SimplifyFDivInst(Value *Op0, Value *Op1, const TargetData *TD,
   return ::SimplifyFDivInst(Op0, Op1, TD, DT, RecursionLimit);
 }
 
+/// SimplifyRem - Given operands for an SRem or URem, see if we can
+/// fold the result.  If not, this returns null.
+static Value *SimplifyRem(Instruction::BinaryOps Opcode, Value *Op0, Value *Op1,
+                          const TargetData *TD, const DominatorTree *DT,
+                          unsigned MaxRecurse) {
+  if (Constant *C0 = dyn_cast<Constant>(Op0)) {
+    if (Constant *C1 = dyn_cast<Constant>(Op1)) {
+      Constant *Ops[] = { C0, C1 };
+      return ConstantFoldInstOperands(Opcode, C0->getType(), Ops, 2, TD);
+    }
+  }
+
+  bool isSigned = Opcode == Instruction::SRem;
+
+  // X % undef -> undef
+  if (match(Op1, m_Undef()))
+    return Op1;
+
+  // undef % X -> 0
+  if (match(Op0, m_Undef()))
+    return Constant::getNullValue(Op0->getType());
+
+  // 0 % X -> 0, we don't need to preserve faults!
+  if (match(Op0, m_Zero()))
+    return Op0;
+
+  // X % 0 -> undef, we don't need to preserve faults!
+  if (match(Op1, m_Zero()))
+    return UndefValue::get(Op0->getType());
+
+  // X % 1 -> 0
+  if (match(Op1, m_One()))
+    return Constant::getNullValue(Op0->getType());
+
+  if (Op0->getType()->isIntegerTy(1))
+    // It can't be remainder by zero, hence it must be remainder by one.
+    return Constant::getNullValue(Op0->getType());
+
+  // X % X -> 0
+  if (Op0 == Op1)
+    return Constant::getNullValue(Op0->getType());
+
+  // If the operation is with the result of a select instruction, check whether
+  // operating on either branch of the select always yields the same value.
+  if (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
+    if (Value *V = ThreadBinOpOverSelect(Opcode, Op0, Op1, TD, DT, MaxRecurse))
+      return V;
+
+  // If the operation is with the result of a phi instruction, check whether
+  // operating on all incoming values of the phi always yields the same value.
+  if (isa<PHINode>(Op0) || isa<PHINode>(Op1))
+    if (Value *V = ThreadBinOpOverPHI(Opcode, Op0, Op1, TD, DT, MaxRecurse))
+      return V;
+
+  return 0;
+}
+
+/// SimplifySRemInst - Given operands for an SRem, see if we can
+/// fold the result.  If not, this returns null.
+static Value *SimplifySRemInst(Value *Op0, Value *Op1, const TargetData *TD,
+                               const DominatorTree *DT, unsigned MaxRecurse) {
+  if (Value *V = SimplifyRem(Instruction::SRem, Op0, Op1, TD, DT, MaxRecurse))
+    return V;
+
+  return 0;
+}
+
+Value *llvm::SimplifySRemInst(Value *Op0, Value *Op1, const TargetData *TD,
+                              const DominatorTree *DT) {
+  return ::SimplifySRemInst(Op0, Op1, TD, DT, RecursionLimit);
+}
+
+/// SimplifyURemInst - Given operands for a URem, see if we can
+/// fold the result.  If not, this returns null.
+static Value *SimplifyURemInst(Value *Op0, Value *Op1, const TargetData *TD,
+                               const DominatorTree *DT, unsigned MaxRecurse) {
+  if (Value *V = SimplifyRem(Instruction::URem, Op0, Op1, TD, DT, MaxRecurse))
+    return V;
+
+  return 0;
+}
+
+Value *llvm::SimplifyURemInst(Value *Op0, Value *Op1, const TargetData *TD,
+                              const DominatorTree *DT) {
+  return ::SimplifyURemInst(Op0, Op1, TD, DT, RecursionLimit);
+}
+
+static Value *SimplifyFRemInst(Value *Op0, Value *Op1, const TargetData *,
+                               const DominatorTree *, unsigned) {
+  // undef % X -> undef    (the undef could be a snan).
+  if (match(Op0, m_Undef()))
+    return Op0;
+
+  // X % undef -> undef
+  if (match(Op1, m_Undef()))
+    return Op1;
+
+  return 0;
+}
+
+Value *llvm::SimplifyFRemInst(Value *Op0, Value *Op1, const TargetData *TD,
+                              const DominatorTree *DT) {
+  return ::SimplifyFRemInst(Op0, Op1, TD, DT, RecursionLimit);
+}
+
 /// SimplifyShift - Given operands for an Shl, LShr or AShr, see if we can
 /// fold the result.  If not, this returns null.
 static Value *SimplifyShift(unsigned Opcode, Value *Op0, Value *Op1,
@@ -1994,6 +2099,9 @@ static Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
   case Instruction::SDiv: return SimplifySDivInst(LHS, RHS, TD, DT, MaxRecurse);
   case Instruction::UDiv: return SimplifyUDivInst(LHS, RHS, TD, DT, MaxRecurse);
   case Instruction::FDiv: return SimplifyFDivInst(LHS, RHS, TD, DT, MaxRecurse);
+  case Instruction::SRem: return SimplifySRemInst(LHS, RHS, TD, DT, MaxRecurse);
+  case Instruction::URem: return SimplifyURemInst(LHS, RHS, TD, DT, MaxRecurse);
+  case Instruction::FRem: return SimplifyFRemInst(LHS, RHS, TD, DT, MaxRecurse);
   case Instruction::Shl:
     return SimplifyShlInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false,
                            TD, DT, MaxRecurse);
@@ -2088,6 +2196,15 @@ Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD,
   case Instruction::FDiv:
     Result = SimplifyFDivInst(I->getOperand(0), I->getOperand(1), TD, DT);
     break;
+  case Instruction::SRem:
+    Result = SimplifySRemInst(I->getOperand(0), I->getOperand(1), TD, DT);
+    break;
+  case Instruction::URem:
+    Result = SimplifyURemInst(I->getOperand(0), I->getOperand(1), TD, DT);
+    break;
+  case Instruction::FRem:
+    Result = SimplifyFRemInst(I->getOperand(0), I->getOperand(1), TD, DT);
+    break;
   case Instruction::Shl:
     Result = SimplifyShlInst(I->getOperand(0), I->getOperand(1),
                              cast<BinaryOperator>(I)->hasNoSignedWrap(),

lib/Transforms/InstCombine/InstCombineMulDivRem.cpp

@@ -492,28 +492,6 @@ Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
   return 0;
 }
 
-/// This function implements the transforms on rem instructions that work
-/// regardless of the kind of rem instruction it is (urem, srem, or frem). It 
-/// is used by the visitors to those instructions.
-/// @brief Transforms common to all three rem instructions
-Instruction *InstCombiner::commonRemTransforms(BinaryOperator &I) {
-  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
-
-  if (isa<UndefValue>(Op0)) {             // undef % X -> 0
-    if (I.getType()->isFPOrFPVectorTy())
-      return ReplaceInstUsesWith(I, Op0);  // X % undef -> undef (could be SNaN)
-    return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
-  }
-  if (isa<UndefValue>(Op1))
-    return ReplaceInstUsesWith(I, Op1);  // X % undef -> undef
-
-  // Handle cases involving: rem X, (select Cond, Y, Z)
-  if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
-    return &I;
-
-  return 0;
-}
-
 /// This function implements the transforms common to both integer remainder
 /// instructions (urem and srem). It is called by the visitors to those integer
 /// remainder instructions.
@@ -521,26 +499,11 @@ Instruction *InstCombiner::commonRemTransforms(BinaryOperator &I) {
 Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
 
-  if (Instruction *common = commonRemTransforms(I))
-    return common;
-
-  // X % X == 0
-  if (Op0 == Op1)
-    return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
-
-  // 0 % X == 0 for integer, we don't need to preserve faults!
-  if (Constant *LHS = dyn_cast<Constant>(Op0))
-    if (LHS->isNullValue())
-      return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
+  // Handle cases involving: rem X, (select Cond, Y, Z)
+  if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
+    return &I;
 
   if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
-    // X % 0 == undef, we don't need to preserve faults!
-    if (RHS->equalsInt(0))
-      return ReplaceInstUsesWith(I, UndefValue::get(I.getType()));
-    
-    if (RHS->equalsInt(1))  // X % 1 == 0
-      return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
-
     if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
       if (SelectInst *SI = dyn_cast<SelectInst>(Op0I)) {
         if (Instruction *R = FoldOpIntoSelect(I, SI))
@@ -562,6 +525,9 @@ Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
 Instruction *InstCombiner::visitURem(BinaryOperator &I) {
   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
 
+  if (Value *V = SimplifyURemInst(Op0, Op1, TD))
+    return ReplaceInstUsesWith(I, V);
+
   if (Instruction *common = commonIRemTransforms(I))
     return common;
   
@@ -602,6 +568,9 @@ Instruction *InstCombiner::visitURem(BinaryOperator &I) {
 Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
 
+  if (Value *V = SimplifySRemInst(Op0, Op1, TD))
+    return ReplaceInstUsesWith(I, V);
+
   // Handle the integer rem common cases
   if (Instruction *Common = commonIRemTransforms(I))
     return Common;
@@ -660,6 +629,14 @@ Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
 }
 
 Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
-  return commonRemTransforms(I);
-}
+  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
 
+  if (Value *V = SimplifyFRemInst(Op0, Op1, TD))
+    return ReplaceInstUsesWith(I, V);
+
+  // Handle cases involving: rem X, (select Cond, Y, Z)
+  if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
+    return &I;
+
+  return 0;
+}

test/Transforms/InstSimplify/rem.ll

@@ -0,0 +1,17 @@
+; RUN: opt < %s -instsimplify -S | FileCheck %s
+
+define i32 @select1(i32 %x, i1 %b) {
+; CHECK: @select1
+  %rhs = select i1 %b, i32 %x, i32 1
+  %rem = srem i32 %x, %rhs
+  ret i32 %rem
+; CHECK: ret i32 0
+}
+
+define i32 @select2(i32 %x, i1 %b) {
+; CHECK: @select2
+  %rhs = select i1 %b, i32 %x, i32 1
+  %rem = urem i32 %x, %rhs
+  ret i32 %rem
+; CHECK: ret i32 0
+}