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[InstCombine] fix vector shuffle transform to replace undef elements (PR37648)

Authored by spatel on Jun 1 2018, 12:23 PM.

Description

[InstCombine] fix vector shuffle transform to replace undef elements (PR37648)

This bug:
https://bugs.llvm.org/show_bug.cgi?id=37648
...was created with the enhancement to this transform with rL332479.

The urem test shows the disaster potential: any undef divisor lane makes
the whole op undef.

The test diffs show that vector demanded elements turns some of the potential,
but not all, unused binop operands back into undef already.

llvm-svn: 333782

Details

Committed
spatelJun 1 2018, 12:23 PM
Parents
rG36d457c20d86: [lldb, process] Fix occasional hang when launching a process in LLDB
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