[llvm-commits] CVS: llvm/lib/Transforms/Scalar/InstructionCombining.cpp

[Chris Lattner]

Changes in directory llvm/lib/Transforms/Scalar:

InstructionCombining.cpp updated: 1.98 -> 1.99

---
Log message:

IC: (X & 5) == 13 --> false
IC: (X | 8) == 4  --> false


---
Diffs of the changes:

Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp
diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.98 llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.99
--- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.98	Wed Jul 23 10:22:24 2003
+++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp	Wed Jul 23 12:02:11 2003
@@ -697,15 +697,35 @@
   // integers at the end of their ranges...
   //
   if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
-    if (CI->isNullValue()) {
-      if (I.getOpcode() == Instruction::SetNE)
-        return new CastInst(Op0, Type::BoolTy, I.getName());
-      else if (I.getOpcode() == Instruction::SetEQ) {
+    // Simplify seteq and setne instructions...
+    if (I.getOpcode() == Instruction::SetEQ ||
+        I.getOpcode() == Instruction::SetNE) {
+      bool isSetNE = I.getOpcode() == Instruction::SetNE;
+
+      if (CI->isNullValue()) {   // Simplify [seteq|setne] X, 0
+        CastInst *Val = new CastInst(Op0, Type::BoolTy, I.getName()+".not");
+        if (isSetNE) return Val;
+
         // seteq X, 0 -> not (cast X to bool)
-        Instruction *Val = new CastInst(Op0, Type::BoolTy, I.getName()+".not");
         InsertNewInstBefore(Val, I);
         return BinaryOperator::createNot(Val, I.getName());
       }
+
+      // If the first operand is (and|or) with a constant, and the second
+      // operand is a constant, simplify a bit.
+      if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
+        if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1)))
+          if (BO->getOpcode() == Instruction::Or) {
+            // If bits are being or'd in that are not present in the constant we
+            // are comparing against, then the comparison could never succeed!
+            if (!(*BOC & *~*CI)->isNullValue())
+              return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
+          } else if (BO->getOpcode() == Instruction::And) {
+            // If bits are being compared against that are and'd out, then the
+            // comparison can never succeed!
+            if (!(*CI & *~*BOC)->isNullValue())
+              return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
+          }
     }
 
     // Check to see if we are comparing against the minimum or maximum value...