[llvm-commits] [llvm] r52315 - in /llvm/trunk: include/llvm/Analysis/ValueTracking.h lib/Analysis/ValueTracking.cpp lib/Transforms/Scalar/InstructionCombining.cpp

[Matthijs Kooijman]

Hi Chris,

> Can't passes just insert a new ExtractValueInst and expect instcombine  
> to simplify stuff away?
Currently, this method is only used by SCCP, IPConstProp and InstCombine
itself. The first two use it to propagate constants or known values out of
functions (ie, propage known return values). This means they really have to
try to find the actual value instead of just inserting extractvalue.

We could probably reduce this to only look at the first level of inserts or
something, but that would require always running instcombine before these
passes (which ends up being slower, I would expect) and causes some
simplifications to be left out.

So, I don't think changing this is the way to go.

Gr.

Matthijs
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