commit c4a68ddfbf2ad447212733fe40e15c730b4357c5
author Sanjay Patel <spatel@rotateright.com> Thu Mar 21 13:57:07 2019 +0000
committer Sanjay Patel <spatel@rotateright.com> Thu Mar 21 13:57:07 2019 +0000
tree 5e41b3d3c13a0143a57c08ac4ccde4221a8df301
parent 380737bf6dbbe64044cc67bde06f3d31e13c0155

[CodeGenPrepare] limit formation of overflow intrinsics (PR41129)

This is probably a bigger limitation than necessary, but since we don't have any evidence yet
that this transform led to real-world perf improvements rather than regressions, I'm making a
quick, blunt fix.

In the motivating x86 example from:
https://bugs.llvm.org/show_bug.cgi?id=41129
...and shown in the regression test, we want to avoid an extra instruction in the dominating
block because that could be costly.

The x86 LSR test diff is reversing the changes from D57789. There's no evidence that 1 version
is any better than the other yet.

Differential Revision: https://reviews.llvm.org/D59602

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356665 91177308-0d34-0410-b5e6-96231b3b80d8