[llvm-commits] [llvm] r89959 - in /llvm/trunk: include/llvm/Analysis/ValueTracking.h lib/Analysis/ValueTracking.cpp test/Analysis/BasicAA/gep-alias.ll

[Duncan Sands]

Hi Chris,

> +  /// The scaled symbolic offsets (represented by pairs of a Value* and a scale
> +  /// in the VarIndices vector) are Value*'s that are known to be scaled by the
> +  /// specified amount, but which may have other unrepresented high bits. As
> +  /// such, the gep cannot necessarily be reconstructed from its decomposed
> +  /// form.

it looks like there is no control on how many bits are "unrepresented high
bits".  For example, if you had an extension from i1 somewhere, presumably
all bits except the first may contain some rubbish values.  If you now do
a test like "is this value bigger than 4", how can you answer?

Ciao,

Duncan.