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

[Chris Lattner]

Changes in directory llvm/lib/Transforms/Scalar:

InstructionCombining.cpp updated: 1.161 -> 1.162

---
Log message:

Fix InstCombine/2004-02-23-ShiftShiftOverflow.ll
Also, turn 'shr int %X, 1234' into 'shr int %X, 31'



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Diffs of the changes:  (+10 -3)

Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp
diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.161 llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.162
--- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.161	Mon Feb 23 01:16:20 2004
+++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp	Mon Feb 23 14:30:06 2004
@@ -1570,9 +1570,14 @@
     // of a signed value.
     //
     unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
-    if (CUI->getValue() >= TypeBits &&
-        (!Op0->getType()->isSigned() || isLeftShift))
-      return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
+    if (CUI->getValue() >= TypeBits) {
+      if (!Op0->getType()->isSigned() || isLeftShift)
+        return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
+      else {
+        I.setOperand(1, ConstantUInt::get(Type::UByteTy, TypeBits-1));
+        return &I;
+      }
+    }
 
     // ((X*C1) << C2) == (X * (C1 << C2))
     if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
@@ -1636,6 +1641,8 @@
         // Check for (A << c1) << c2   and   (A >> c1) >> c2
         if (I.getOpcode() == Op0SI->getOpcode()) {
           unsigned Amt = ShiftAmt1+ShiftAmt2;   // Fold into one big shift...
+          if (Op0->getType()->getPrimitiveSize()*8 < Amt)
+            Amt = Op0->getType()->getPrimitiveSize()*8;
           return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
                                ConstantUInt::get(Type::UByteTy, Amt));
         }