[PATCH] Fix a performance problem in gep(gep ...) merging

[Quentin Colombet]

Hi Wei,

Could you upload the context with your patch to ease the review?

Thanks,
-Quentin


REPOSITORY
  rL LLVM

================
Comment at: lib/Transforms/InstCombine/InstructionCombining.cpp:1474
@@ +1473,2 @@
+        if (!isa<Constant>(GO1) || !isa<Constant>(SO1))
+          return nullptr;
----------------
Without the context, this is hard to say whether or not this is true.
In particular, if the new GEP can be folded in an addressing mode, this is good for the register pressure.

http://reviews.llvm.org/D8911

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