[PATCH] D44282: [PR16756] JumpThreading: explicitly update SSA rather than use SSAUpdater.

[Michael Zolotukhin via Phabricator via llvm-commits]

mzolotukhin added a comment.

Hi,

I created a separate class for bulk SSA updates. With that implementation, we recompute IDF for every individual variable, but usually the subgraph we're working with is smaller. In the previous implementation we computed IDF once for the union of these subgraphs - that was faster, but also we might accidentally insert unneeded phi-nodes, which we later had to clean-up.

I tried to make the interface close to the existing one, and included an example of how it can be used in JumpThreading (if this change is approved, I'll commit these parts separately). With this change, the speedup on the original test is smaller, but still quite good:

  ===-------------------------------------------------------------------------===
    Total Execution Time: 15.0158 seconds (15.0163 wall clock)
  
     ---User Time---   --System Time--   --User+System--   ---Wall Time---  --- Name ---
     4.5962 ( 31.5%)   0.0170 (  3.8%)   4.6132 ( 30.7%)   4.6142 ( 30.7%)  Jump Threading
     3.1789 ( 21.8%)   0.0049 (  1.1%)   3.1838 ( 21.2%)   3.1838 ( 21.2%)  Jump Threading
     1.2104 (  8.3%)   0.1836 ( 41.5%)   1.3940 (  9.3%)   1.3942 (  9.3%)  X86 DAG->DAG Instruction Selection
     1.3558 (  9.3%)   0.0020 (  0.5%)   1.3578 (  9.0%)   1.3577 (  9.0%)  SLP Vectorizer

What do you think?

Thanks,
Michael

PS: Ideas for a better class name are welcome!


Repository:
  rL LLVM

https://reviews.llvm.org/D44282