On Thu, 2007-03-29 at 23:08 -0700, Chris Lattner wrote: > On Mar 28, 2007, at 6:57 PM, Zhou Sheng wrote: > > > @@ -540,8 +540,10 @@ > > if (I->getOpcode() == Instruction::Shl) > > if ((CST = dyn_cast<ConstantInt>(I->getOperand(1)))) { > > // The multiplier is really 1 << CST. > > - Constant *One = ConstantInt::get(V->getType(), 1); > > - CST = cast<ConstantInt>(ConstantExpr::getShl(One, CST)); > > + uint32_t BitWidth = cast<IntegerType>(V->getType())- > > >getBitWidth(); > > + uint32_t CSTVal = CST->getValue().getActiveBits() > 64 ? > > + BitWidth : CST->getZExtValue(); > > + CST = ConstantInt::get(APInt(BitWidth, 1).shl(CSTVal)); > > return I->getOperand(0); > > } > > } > > I don't understand the logic here for the >64 active bits case. Is > the idea that the operation is undefined anyway?
Yes. The CST constant is the operand 1 of a shift, the shift amount. As you noted in previous commits, we have to guard against using getZExtValue even on shift amounts because they could be huge (> 64 bits). In such situations, we just set the shift amount to the bit width (also undefined) and avoid the getZExtValue (and avoid the assert). There will be several more of these. Actually I asked Sheng to change these to use a new method on ConstantInt since the idiom appears to be cropping up all over the place (every shift examination). Reid. > > -Chris > _______________________________________________ > llvm-commits mailing list > llvm-commits@cs.uiuc.edu > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits _______________________________________________ llvm-commits mailing list llvm-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits