[PATCH] D89381: [SCEV] Re-enable "Use nw flag and symbolic iteration count to sharpen ranges of AddRecs", attempt 3

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev added a comment.

Here's the study that I made on the example of rdopt_coding_state. Units below are Ir (hopefully it's "instructions retired") on compilation with clang O3 <https://reviews.llvm.org/owners/package/3/>.

Almost queries are made for `start = 0`, constant step & BE count expression that varies from small to really huge expressions.
IR without patch: 220370413
IR with previous version of patch (no SCEV size limits): 224114149 (2% regression).
When I started limiting the size of IRs involved in transform, the dynamics was following:
Limit = 2: 220517261
Limit = 3: 221761742
Limit = 4-6: 222841240

So starting size 4, we have 1% regression on this test (but wide picture might be different). In the patch I set the limit of 6 because it's the minimum value needed to pass all tests in the way as they passed without limits. @nikic could you please evaluate this one?


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