[llvm-commits] [llvm] r91811 - in /llvm/trunk: lib/Transforms/Scalar/InstructionCombining.cpp test/Transforms/InstCombine/icmp.ll

[Duncan Sands]

Hi Chris,

> +  // From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0,
> +  // so the values can never be equal.  Similiarly for all other "or equals"
> +  // operators.
> +  
> +  // (X+1) <u X        --> X >u (MAXUINT-1)        --> X != 255

X != 255 should be X == 255

> +  if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
> +    Value *R = ConstantExpr::getSub(ConstantInt::get(CI->getType(), -1ULL), CI);

Shouldn't this use ConstantInt::getAllOnesValue not -1ULL, in case these are
very wide integers?

As a meta point, if you have the NSW/NUW flags set, you can avoid worrying about
the overflow cases.

Ciao,

Duncan.