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[CodeGenPrepare] limit formation of overflow intrinsics (PR41129)

Authored by spatel on Mar 21 2019, 6:57 AM.

Description

[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

llvm-svn: 356665

Details

Committed
spatelMar 21 2019, 6:57 AM
Differential Revision
D59602: [CodeGenPrepare] limit formation of overflow intrinsics (PR41129)
Parents
rG3e9e55491e78: [llvm-readobj] Format codes. NFC.
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