If the gep is nusw (usually via inbounds) and the offset is
non-negative, we can infer nuw.

Proof: https://alive2.llvm.org/ce/z/ihztLy

This patch tries to flip the signedness of predicates when folding an
unsigned icmp with a signed min/max. It will enable more optimizations
as we canonicalizes a signed icmp into an unsigned icmp when both
operands are known to have the same sign.
Fixes #76672.

Compile-time impact:
http://llvm-compile-time-tracker.com/compare.php?from=949ec83eaf6fa6dbffb94c2ea9c0a4d5efdbd239&to=2deca1aea8a4e13609bab72c522a97d424f0fc2d&stat=instructions:u


|stage1-O3|stage1-ReleaseThinLTO|stage1-ReleaseLTO-g|stage1-O0-g|stage2-O3|stage2-O0-g|stage2-clang|
|--|--|--|--|--|--|--|
|-0.00%|+0.01%|+0.05%|-0.12%|-0.01%|-0.03%|-0.00%|

NOTE: We can flip the signedness of predicate if both operands are
negative. But I don't see the benefit of handling these cases.

The disjoint flag was recently added to IR in #72583 

We were failing to set the known bits for add/sub in the multi-use
case, resulting in odd behavioral differences depending on the
number of uses. Noticed while adding a consistency assertion.

The test changes are essentially a revert to the state before
d6498ab. These changes are not really desirable, but if we don't
want them, that needs to be handled as part of the heuristic for
demanded constant shrinking, not by artifically suppressing the
known bits in one specific case.

For `smin` if either `X` or `Y` is negative, the result is non-zero.
For `smax` if either `X` or `Y` is strictly positive, the result is
non-zero.

For both if `X != 0` and `Y != 0` the result is non-zero.

Alive2 Link:
    https://alive2.llvm.org/ce/z/7yvbgN
    https://alive2.llvm.org/ce/z/zizbvq

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D149417

This is the first patch in a series intended for removing flag
-enable-new-pm=0 from lit tests. This is part of a bigger
effort of completely removing legacy code related to legacy
pass manager in favor of currently default new pass manager.

In this patch flag has been removed only from tests where no significant
change has been required because checks has been duplicated for
both PMs.

Reviewed By: fhahn

Differential Revision: https://reviews.llvm.org/D134150

This was originally part of D133788. There are no visible
regressions. All of the diffs show a large unsigned constant
becoming a small negative constant. This should be better
for analysis (and slightly less compile-time) and codegen.

The basic idea to this is that a) having a single canonical type makes CSE easier, and b) many of our transforms are inconsistent about which types we end up with based on visit order.

I'm restricting this to constants as for non-constants, we'd have to decide whether the simplicity was worth extra instructions. For constants, there are no extra instructions.

We chose the canonical type as i64 arbitrarily.  We might consider changing this to something else in the future if we have cause.

Differential Revision: https://reviews.llvm.org/D115387