[PATCH] D123394: [CodeGen] Late cleanup of redundant address/immediate definitions.

[Philip Reames via Phabricator via llvm-commits]

reames added a comment.

This looks very interesting.  I've been thinking about ways to improve stack addressing sequences on RISCV, and this nicely tackles many of the cases I was just thinking about.

Unfortunately, I think the patch as landed is wrong.  See the inline comment on an example where we can't forward due to a clobber which doesn't appear to be respected.



================
Comment at: llvm/test/CodeGen/RISCV/rvv/rv64-spill-zvlsseg.ll:44
 ; SPILL-O2-NEXT:    #NO_APP
-; SPILL-O2-NEXT:    addi a0, sp, 16
-; SPILL-O2-NEXT:    csrr a1, vlenb
----------------
This line looks to be wrong.  a0 is clobbered on line 40 which is after the previous definition being forwarded from line 37.  


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  https://reviews.llvm.org/D123394/new/

https://reviews.llvm.org/D123394