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[InstCombine] Sanitize undef vector constant to 1 in X*(2^C) with X << C…

Authored by lebedev.ri on Aug 12 2020, 11:06 AM.

Description

[InstCombine] Sanitize undef vector constant to 1 in X*(2^C) with X << C (PR47133)

While x*undef is undef, shift-by-undef is poison,
which we must avoid introducing.

Also log2(iN undef) is *NOT* iN undef, because log2(iN undef) u< N.

See https://bugs.llvm.org/show_bug.cgi?id=47133

Details

Committed
lebedev.riAug 12 2020, 12:06 PM
Parents
rGc561f4d2ec19: [SVE][VLS] Don't combine logical AND.
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