[CVP] After proving that @llvm.with.overflow()/@llvm.sat() don't overflow, also…

Authored by lebedev.ri on Oct 18 2019, 12:32 PM.


[CVP] After proving that @llvm.with.overflow()/@llvm.sat() don't overflow, also try to prove other no-wrap

CVP, unlike InstCombine, does not run till exaustion.
It only does a single pass.

When dealing with those special binops, if we prove that they can
safely be demoted into their usual binop form,
we do set the no-wrap we deduced. But when dealing with usual binops,
we try to deduce both no-wraps.

So if we convert e.g. @llvm.uadd.with.overflow() to add nuw,
we won't attempt to check whether it can be add nuw nsw.

This patch proposes to call processBinOp() on newly-created binop,
which is identical to what we do for div/rem already.

Reviewers: nikic, spatel, reames

Reviewed By: nikic

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69183

llvm-svn: 375273