[PATCH] D136015: [InstCombine] Fold series of instructions into mull

[Allen zhong via Phabricator via llvm-commits]

Allen added a comment.

Thanks for your attention, I do this as there is case  https://godbolt.org/z/x5jMhqW8s is our benchmark,
and the source is equel to an mull operater for two 64bits integer vaules, so it should be fold to similar assemble.
This is the 1st step try to generate the **mul**. so now I only enable it with `i64` as the instruction **umulh**.

  mul   x8,x1,x0
  umulh x9,x0,x1
  str   x8,[x2]
  str   x9,[x3]




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  https://reviews.llvm.org/D136015/new/

https://reviews.llvm.org/D136015