On Aug 26, 2012, at 11:37 PM, Ted Kremenek <kreme...@apple.com> wrote:
> On Aug 25, 2012, at 12:09 PM, Chris Lattner <clatt...@apple.com> wrote: > >>> Teach CFG that 'if (x & 0)' and 'if (x * 0)' is an unfeasible branch. >> >> Why not teach the general front-end constant folding logic (in >> lib/AST/ExprConstant.cpp) to handle this identity, and then just use it? > > I may have misunderstood the point of ExprConstant, but I thought it's > semantics are tied to restrictions on what we can consider an integer > constant expression. Is that not the case? The "Expr::isIntegerConstantExpr" and "isCXX11ConstantExpr" are limited to folding exactly what the standards spec specifies. EvaluateAsRValue and EvaluateAsInt can use "any crazy technique that we want to" :-) -Chris
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