[InstCombine] Remove the zextOrTrunc from ShrinkDemandedConstant.

The demanded mask and the constant should always be the same width for all callers today.

Also stop copying the demanded mask as its passed in. We should avoid allocating memory unless we are going to do something. The final AND to create the new constant will take care of it.

llvm-svn: 300927

1 files changed, 2 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index b1bd5593f6f..2f6e411345f 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -26,7 +26,7 @@ using namespace llvm::PatternMatch;
 /// 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) {
+                                   const APInt &Demanded) {
   assert(I && "No instruction?");
   assert(OpNo < I->getNumOperands() && "Operand index too large");
 
@@ -37,13 +37,11 @@ static bool ShrinkDemandedConstant(Instruction *I, unsigned OpNo,
     return false;
 
   // If there are no bits set that aren't demanded, nothing to do.
-  Demanded = Demanded.zextOrTrunc(C->getBitWidth());
   if (C->isSubsetOf(Demanded))
     return false;
 
   // This instruction is producing bits that are not demanded. Shrink the RHS.
-  Demanded &= *C;
-  I->setOperand(OpNo, ConstantInt::get(Op->getType(), Demanded));
+  I->setOperand(OpNo, ConstantInt::get(Op->getType(), *C & Demanded));
 
   return true;
 }