move some select simplifications out out instcombine into

inst simplify.  No functionality change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101873 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/InstructionSimplify.h

@@ -46,6 +46,10 @@ namespace llvm {
   Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
                           const TargetData *TD = 0);
   
+  /// SimplifySelectInst - Given operands for a SelectInst, see if we can fold
+  /// the result.  If not, this returns null.
+  Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
+                            const TargetData *TD = 0);
 
   /// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can
   /// fold the result.  If not, this returns null.

lib/Analysis/InstructionSimplify.cpp

@@ -314,6 +314,35 @@ Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
   return 0;
 }
 
+/// SimplifySelectInst - Given operands for a SelectInst, see if we can fold
+/// the result.  If not, this returns null.
+Value *llvm::SimplifySelectInst(Value *CondVal, Value *TrueVal, Value *FalseVal,
+                                const TargetData *TD) {
+  // select true, X, Y  -> X
+  // select false, X, Y -> Y
+  if (ConstantInt *CB = dyn_cast<ConstantInt>(CondVal))
+    return CB->getZExtValue() ? TrueVal : FalseVal;
+  
+  // select C, X, X -> X
+  if (TrueVal == FalseVal)
+    return TrueVal;
+  
+  if (isa<UndefValue>(TrueVal))   // select C, undef, X -> X
+    return FalseVal;
+  if (isa<UndefValue>(FalseVal))   // select C, X, undef -> X
+    return TrueVal;
+  if (isa<UndefValue>(CondVal)) {  // select undef, X, Y -> X or Y
+    if (isa<Constant>(TrueVal))
+      return TrueVal;
+    return FalseVal;
+  }
+  
+  
+  
+  return 0;
+}
+
+
 /// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can
 /// fold the result.  If not, this returns null.
 Value *llvm::SimplifyGEPInst(Value *const *Ops, unsigned NumOps,
@@ -391,6 +420,9 @@ Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD) {
   case Instruction::FCmp:
     return SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
                             I->getOperand(0), I->getOperand(1), TD);
+  case Instruction::Select:
+    return SimplifySelectInst(I->getOperand(0), I->getOperand(1),
+                              I->getOperand(2), TD);
   case Instruction::GetElementPtr: {
     SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
     return SimplifyGEPInst(&Ops[0], Ops.size(), TD);

lib/Transforms/InstCombine/InstCombineSelect.cpp

@@ -13,6 +13,7 @@
 
 #include "InstCombine.h"
 #include "llvm/Support/PatternMatch.h"
+#include "llvm/Analysis/InstructionSimplify.h"
 using namespace llvm;
 using namespace PatternMatch;
 
@@ -421,49 +422,30 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
   Value *TrueVal = SI.getTrueValue();
   Value *FalseVal = SI.getFalseValue();
 
-  // select true, X, Y  -> X
+  if (Value *V = SimplifySelectInst(CondVal, TrueVal, FalseVal, TD))
-  // select false, X, Y -> Y
+    return ReplaceInstUsesWith(SI, V);
-  if (ConstantInt *C = dyn_cast<ConstantInt>(CondVal))
-    return ReplaceInstUsesWith(SI, C->getZExtValue() ? TrueVal : FalseVal);
-
-  // select C, X, X -> X
-  if (TrueVal == FalseVal)
-    return ReplaceInstUsesWith(SI, TrueVal);
-
-  if (isa<UndefValue>(TrueVal))   // select C, undef, X -> X
-    return ReplaceInstUsesWith(SI, FalseVal);
-  if (isa<UndefValue>(FalseVal))   // select C, X, undef -> X
-    return ReplaceInstUsesWith(SI, TrueVal);
-  if (isa<UndefValue>(CondVal)) {  // select undef, X, Y -> X or Y
-    if (isa<Constant>(TrueVal))
-      return ReplaceInstUsesWith(SI, TrueVal);
-    else
-      return ReplaceInstUsesWith(SI, FalseVal);
-  }
 
   if (SI.getType()->isIntegerTy(1)) {
     if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) {
       if (C->getZExtValue()) {
         // Change: A = select B, true, C --> A = or B, C
         return BinaryOperator::CreateOr(CondVal, FalseVal);
-      } else {
-        // Change: A = select B, false, C --> A = and !B, C
-        Value *NotCond =
-          InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
-                                             "not."+CondVal->getName()), SI);
-        return BinaryOperator::CreateAnd(NotCond, FalseVal);
       }
+      // Change: A = select B, false, C --> A = and !B, C
+      Value *NotCond =
+        InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
+                                           "not."+CondVal->getName()), SI);
+      return BinaryOperator::CreateAnd(NotCond, FalseVal);
     } else if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) {
       if (C->getZExtValue() == false) {
         // Change: A = select B, C, false --> A = and B, C
         return BinaryOperator::CreateAnd(CondVal, TrueVal);
-      } else {
-        // Change: A = select B, C, true --> A = or !B, C
-        Value *NotCond =
-          InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
-                                             "not."+CondVal->getName()), SI);
-        return BinaryOperator::CreateOr(NotCond, TrueVal);
       }
+      // Change: A = select B, C, true --> A = or !B, C
+      Value *NotCond =
+        InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
+                                           "not."+CondVal->getName()), SI);
+      return BinaryOperator::CreateOr(NotCond, TrueVal);
     }
     
     // select a, b, a  -> a&b