[llvm-commits] [llvm] r53167 - /llvm/trunk/lib/Analysis/ScalarEvolution.cpp

[Nick Lewycky]

Author: nicholas
Date: Mon Jul  7 01:15:49 2008
New Revision: 53167

URL: http://llvm.org/viewvc/llvm-project?rev=53167&view=rev
Log:
Handle 'lshr' instruction with SCEVUDiv object.
Comment the xor %x, -1 case.

Modified:
    llvm/trunk/lib/Analysis/ScalarEvolution.cpp

Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=53167&r1=53166&r2=53167&view=diff

==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Mon Jul  7 01:15:49 2008
@@ -1742,12 +1742,14 @@
     }
     break;
   case Instruction::Xor:
-    // If the RHS of the xor is a signbit, then this is just an add.
-    // Instcombine turns add of signbit into xor as a strength reduction step.
     if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
+      // If the RHS of the xor is a signbit, then this is just an add.
+      // Instcombine turns add of signbit into xor as a strength reduction step.
       if (CI->getValue().isSignBit())
         return SE.getAddExpr(getSCEV(U->getOperand(0)),
                              getSCEV(U->getOperand(1)));
+
+      // If the RHS of xor is -1, then this is a not operation.
       else if (CI->isAllOnesValue())
         return SE.getNotSCEV(getSCEV(U->getOperand(0)));
     }
@@ -1763,6 +1765,16 @@
     }
     break;
 
+  case Instruction::LShr:
+    // Turn logical shift right of a constant into a unsigned divide.
+    if (ConstantInt *SA = dyn_cast<ConstantInt>(U->getOperand(1))) {
+      uint32_t BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
+      Constant *X = ConstantInt::get(
+        APInt(BitWidth, 1).shl(SA->getLimitedValue(BitWidth)));
+      return SE.getUDivExpr(getSCEV(U->getOperand(0)), getSCEV(X));
+    }
+    break;
+
   case Instruction::Trunc:
     return SE.getTruncateExpr(getSCEV(U->getOperand(0)), U->getType());