[PATCH] D70043: [ConstantRange] Add `mulWithNoWrap()` method

[Roman Lebedev via Phabricator via llvm-commits]

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

I'm not happy about this.

Baseline `ConstantRange::mul()` does not have an exhaustive test,
and if i add one (`TestUnsignedBinOpExhaustive()`+`/*CorrectnessOnly=*/true`),
it doesn't pass.

However `mulWithNoWrap` does pass conservatively correctness test.
Though it is less constrained than the brute-force approach.
I don't think it needs a different testing approach though?

Here we don't get `EXPECT_EQ(CR.isEmptySet(), AllOverflow);`
postcondition for free in any of the cases, so it needs to be 
manually enforced. I wonder, shouldn't we be using
`unsigned*?MayOverflow() == OverflowResult::AlwaysOverflowsHigh*`
for that, everywhere? Should be more readable than manual inlined checks..


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D70043

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

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