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

[Chris Lattner]

Changes in directory llvm/lib/Transforms/Scalar:

InstructionCombining.cpp updated: 1.392 -> 1.393
---
Log message:

fold nested and's early to avoid inefficiencies in MaskedValueIsZero.  This
fixes a very slow compile in PR639: http://llvm.cs.uiuc.edu/PR639 .


---
Diffs of the changes:  (+9 -0)

 InstructionCombining.cpp |    9 +++++++++
 1 files changed, 9 insertions(+)


Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp
diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.392 llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.393
--- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.392	Mon Oct 24 01:35:18 2005
+++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp	Wed Oct 26 12:18:16 2005
@@ -1725,6 +1725,15 @@
     // and X, -1 == X
     if (AndRHS->isAllOnesValue())
       return ReplaceInstUsesWith(I, Op0);
+    
+    // and (and X, c1), c2 -> and (x, c1&c2).  Handle this case here, before
+    // calling MaskedValueIsZero, to avoid inefficient cases where we traipse
+    // through many levels of ands.
+    {
+      Value *X; ConstantInt *C1;
+      if (match(Op0, m_And(m_Value(X), m_ConstantInt(C1))))
+        return BinaryOperator::createAnd(X, ConstantExpr::getAnd(C1, AndRHS));
+    }
 
     if (MaskedValueIsZero(Op0, AndRHS))        // LHS & RHS == 0
       return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));