[llvm] [CGP] Reassociate GEPs to separate scalar and vector indexing (PR #146379)

[Philip Reames via llvm-commits]

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@@ -6235,23 +6239,177 @@ bool CodeGenPrepare::optimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
   return true;
 }
 
+Value *CodeGenPrepare::splitLastVectorIndex(Instruction *MemoryInst,
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preames wrote:

This block is just the original code, pulled out into a helper.  I'd originally tried to merge both into a single implementation, but the complexity kept confusing me.  The split structure is much easier to reason about.  

https://github.com/llvm/llvm-project/pull/146379