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Set bit instead of calling pow() to compute 2 << n 

llvm-svn: 85814
This commit is contained in:
Victor Hernandez 2009-11-02 18:51:28 +00:00
parent ec344ed2f5
commit df022f1449
1 changed files with 13 additions and 5 deletions
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16
llvm/lib/Analysis/MemoryBuiltins.cpp
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@ -16,6 +16,7 @@
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/Module.h"
#include "llvm/ADT/APInt.h"
#include "llvm/Analysis/ConstantFolding.h"
using namespace llvm;
@ -156,10 +157,17 @@ static Value* isArrayMallocHelper(const CallInst *CI, LLVMContext &Context,
return Op1;
}
if (Opcode == Instruction::Shl) {
ConstantInt* Op1Int = dyn_cast<ConstantInt>(Op1);
if (!Op1Int) return NULL;
Value* Op1Pow = ConstantInt::get(Op1->getType(), (uint64_t)
pow(2.0, (double) Op1Int->getZExtValue()));
ConstantInt* Op1CI = dyn_cast<ConstantInt>(Op1);
if (!Op1CI) return NULL;
APInt Op1Int = Op1CI->getValue();
unsigned Op1Width = Op1Int.getBitWidth();
// check for overflow
if (Op1Int.getActiveBits() > 64 || Op1Int.getZExtValue() > Op1Width)
return NULL;
Value* Op1Pow = ConstantInt::get(Context,
APInt(Op1Width, 0).set(Op1Int.getZExtValue()));
if (Op0 == ElementSize || (FoldedElementSize && Op0 == FoldedElementSize))
// ArraySize << log2(ElementSize)
return Op1Pow;