[PATCH] D69918: [CR][WIP] Add `subWithNoWrap()` method

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: nikic, shchenz, efriedma.
lebedev.ri added a project: LLVM.
Herald added a subscriber: hiraditya.

Much like D67339 <https://reviews.llvm.org/D67339>, adds ConstantRange handling for
when we know no-wrap behavior of the `sub`.

This is WIP, just barely working enough to post.

As noted in https://reviews.llvm.org/D67339#inline-629306,
there is something wrong with the exhaustive tests,
Those overflow checks in `addWithNoWrap()` aren't needed,
as per test coverage.

Even if i add a check `if every permutation
of ForeachNumInConstantRange()*ForeachNumInConstantRange()` says
there's overflow, then `ConstantRange::*WithNoWrap()` should
have returned Empty set, those overflow checks
are still not needed for `add`. One check is needed for `sub` though.

So, what is the missing check?


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D69918

Files:
  llvm/include/llvm/IR/ConstantRange.h
  llvm/lib/IR/ConstantRange.cpp
  llvm/unittests/IR/ConstantRangeTest.cpp

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