[PATCH] D20907: [IfConversion] Bugfix: don't add Undef flag on use if reg is live.

[Quentin Colombet via llvm-commits]

qcolombet added a subscriber: qcolombet.
qcolombet added a comment.

Hi Jonas,

Undef does not mean dead, just that this specific use does not care what is in the register. So it can be anything.

  /// IsUndef - True if this register operand reads an "undef" value, i.e. the
  /// read value doesn't matter.

Some passes may make this assumption and we should fix them. Which pass does the invalid transformation?

Cheers,
-Quentin


http://reviews.llvm.org/D20907