In rL364135, I taught IndVars to fold exiting branches in loops with a zero backedge taken count (i.e. loops that only run one iteration). This extends that to eliminate the dead comparison left around.
llvm-svn: 364155
This turned out to be surprisingly effective. I was originally doing this just for completeness sake, but it seems like there are a lot of cases where SCEV's exit count reasoning is stronger than it's isKnownPredicate reasoning.
Once this is in, I'm thinking about trying to build on the same infrastructure to eliminate provably untaken checks. There may be something generally interesting here.
Differential Revision: https://reviews.llvm.org/D63618
llvm-svn: 364135
We were only matching RHS being a loop invariant value, not the inverse. Since there's nothing which appears to canonicalize loop invariant values to RHS, this means we missed cases.
Differential Revision: https://reviews.llvm.org/D63112
llvm-svn: 363108
As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
This is a follow-up for the patch rL335020. When we replace compares against
trunc with compares against wide IV, we can also replace signed predicates with
unsigned where it is legal.
Reviewed By: reames
Differential Revision: https://reviews.llvm.org/D48763
llvm-svn: 338115
If a trunc has a user in a block which is not reachable from entry,
we can safely perform trunc elimination as if this user didn't exist.
llvm-svn: 335816
This patch adds logic to deal with the following constructions:
%iv = phi i64 ...
%trunc = trunc i64 %iv to i32
%cmp = icmp <pred> i32 %trunc, %invariant
Replacing it with
%iv = phi i64 ...
%cmp = icmp <pred> i64 %iv, sext/zext(%invariant)
In case if it is legal. Specifically, if `%iv` has signed comparison users, it is
required that `sext(trunc(%iv)) == %iv`, and if it has unsigned comparison
uses then we require `zext(trunc(%iv)) == %iv`. The current implementation
bails if `%trunc` has other uses than `icmp`, but in theory we can handle more
cases here (e.g. if the user of trunc is bitcast).
Differential Revision: https://reviews.llvm.org/D47928
Reviewed By: reames
llvm-svn: 335020
Philip Reames