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
Currently LLVM will generally merge GEPs. This allows backends to use more complex addressing modes. In some cases this is not happening because there is PHI inbetween the two GEPs: GEP1--\ |-->PHI1-->GEP3 GEP2--/ This patch checks to see if GEP1 and GEP2 are similiar enough that they can be cloned (GEP12) in GEP3's BB, allowing GEP->GEP merging (GEP123): GEP1--\ --\ --\ |-->PHI1-->GEP3 ==> |-->PHI2->GEP12->GEP3 == > |-->PHI2->GEP123 GEP2--/ --/ --/ This also breaks certain use chains that are preventing GEP->GEP merges that the the existing instcombine would merge otherwise. Tests included. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209843 91177308-0d34-0410-b5e6-96231b3b80d8