[llvm-commits] [llvm] r90417 - in /llvm/trunk: lib/Target/ARM/ARMISelLowering.cpp test/CodeGen/ARM/2009-12-02-vtrn-undef.ll

[Duncan Sands]

Hi Bob,

> Recognize canonical forms of vector shuffles where the same vector is used for
> both source operands.  In the canonical form, the 2nd operand is changed to an
> undef and the shuffle mask is adjusted to only reference elements from the 1st
> operand.  Radar 7434842.

this sounds like a general optimization, i.e. not ARM specific.  How about doing
this in the DAG combiner instead?

Ciao,

Duncan.