Summary:
This change splits `makeICmpRegion` into `makeAllowedICmpRegion` and
`makeSatisfyingICmpRegion` with slightly different contracts. The first
one is useful for determining what values some expression //may// take,
given that a certain `icmp` evaluates to true. The second one is useful
for determining what values are guaranteed to //satisfy// a given
`icmp`.
Reviewers: nlewycky
Reviewed By: nlewycky
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D8345
llvm-svn: 232575
Multiplication is not dependent on signedness, so just treating
all input ranges as unsigned is not incorrect. However it will cause
overly pessimistic ranges (such as full-set) when used with signed
negative values.
Teach multiply to try to interpret its inputs as both signed and
unsigned, and then to take the most specific (smallest population)
as its result.
llvm-svn: 231483
a bit surprising, as the class is almost entirely abstracted away from
any particular IR, however it encodes the comparsion predicates which
mutate ranges as ICmp predicate codes. This is reasonable as they're
used for both instructions and constants. Thus, it belongs in the IR
library with instructions and constants.
llvm-svn: 202838
Sanjoy Das