Changes in directory llvm/lib/Transforms/Scalar:
InstructionCombining.cpp updated: 1.654 -> 1.655
---
Log message:
Add an APInt version of ShrinkDemandedConstant.
Patch by Zhou Sheng.
---
Diffs of the changes: (+24 -0)
InstructionCombining.cpp | 24 ++++++++++++++++++++++++
1 files changed, 24 insertions(+)
Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp
diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.654
llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.655
--- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.654 Mon Mar 12
11:54:56 2007
+++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp Mon Mar 12 12:15:10 2007
@@ -1004,6 +1004,30 @@
return true;
}
+/// ShrinkDemandedConstant - Check to see if the specified operand of the
+/// specified instruction is a constant integer. If so, check to see if there
+/// are any bits set in the constant that are not demanded. If so, shrink the
+/// constant and return true.
+static bool ShrinkDemandedConstant(Instruction *I, unsigned OpNo,
+ APInt Demanded) {
+ assert(I && "No instruction?");
+ assert(OpNo < I->getNumOperands() && "Operand index too large");
+
+ // If the operand is not a constant integer, nothing to do.
+ ConstantInt *OpC = dyn_cast<ConstantInt>(I->getOperand(OpNo));
+ if (!OpC) return false;
+
+ // If there are no bits set that aren't demanded, nothing to do.
+ Demanded.zextOrTrunc(OpC->getValue().getBitWidth());
+ if ((~Demanded & OpC->getValue()) == 0)
+ return false;
+
+ // This instruction is producing bits that are not demanded. Shrink the RHS.
+ Demanded &= OpC->getValue();
+ I->setOperand(OpNo, ConstantInt::get(Demanded));
+ return true;
+}
+
// ComputeSignedMinMaxValuesFromKnownBits - Given a signed integer type and a
// set of known zero and one bits, compute the maximum and minimum values that
// could have the specified known zero and known one bits, returning them in
_______________________________________________
llvm-commits mailing list
llvm-commits@cs.uiuc.edu
http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
