Inspired by
https://discourse.llvm.org/t/rfc-signedness-independent-icmps/81423

As noted when #82404 was pushed (canonicalizing `sitofp` -> `uitofp`),
different signedness on fp casts can have dramatic performance
implications on different backends.

So, it makes to create a reliable means for the backend to pick its
cast signedness if either are correct.

Further, this allows us to start canonicalizing `sitofp`- > `uitofp`
which may easy middle end analysis.

Closes #86141

This patch adds the nuw (no unsigned wrap) and nsw (no signed wrap)
poison-generating flags to the trunc instruction.

Discourse thread:
https://discourse.llvm.org/t/rfc-add-nowrap-flags-to-trunc/77453

This flag indicates that every bit is known to be zero in at least one
of the inputs. This allows the Or to be treated as an Add since there is
no possibility of a carry from any bit.

If the flag is present and this property does not hold, the result is
poison.

This makes it easier to reverse the InstCombine transform that turns Add
into Or.

This is inspired by a comment here
https://github.com/llvm/llvm-project/pull/71955#discussion_r1391614578

Discourse thread
https://discourse.llvm.org/t/rfc-add-or-disjoint-flag/75036

Add an nneg flag to the zext instruction, which specifies that the
argument is non-negative. Otherwise, the result is a poison value.

The primary use-case for the flag is to preserve information when sext
gets replaced with zext due to range-based canonicalization. The nneg
flag allows us to convert the zext back into an sext later. This is
useful for some optimizations (e.g. a signed icmp can fold with sext but
not zext), as well as some targets (e.g. RISCV prefers sext over zext).

Discourse thread: https://discourse.llvm.org/t/rfc-add-zext-nneg-flag/73914

This patch is based on https://reviews.llvm.org/D156444 by
@Panagiotis156, with some implementation simplifications and additional
tests.

---------

Co-authored-by: Panagiotis K <karouzakispan@gmail.com>

llvm-svn: 216022

Change the default for `-num-shuffles` to 5 and better document the
algorithm in the header docs of `verify-uselistorder`.

llvm-svn: 214419

llvm-svn: 214318

Fix the sort of expected order in the reader to correctly return `false`
when comparing a `Use` against itself.

This was caught by test/Bitcode/binaryIntInstructions.3.2.ll, so I'm
adding a `RUN` line using `llvm-uselistorder` for every test in
`test/Bitcode` that passes.

A few tests still fail, so I'll investigate those next.

This is part of PR5680.

llvm-svn: 214157

of a forward-reference, which doesn't use an "abbrev" encoding.

llvm-svn: 94454