[PATCH] D138050: AMDGPU/GlobalISel: Insert freeze when splitting vector G_SEXT_INREG

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

In D138050#3930454 <https://reviews.llvm.org/D138050#3930454>, @Pierre-vh wrote:

> What makes this combine specifically require a freeze? Could we have more combine that need it to or is it something with G_SEXT_INREG's semantics that makes it need the G_FREEZE?

It's introducing an expectation for potentially poisonous bits in two distinct uses since the low half is used in two different places. Both uses need to use the same value. There are plenty of places that are probably missing freezes

There have been a number of talks on freeze, e.g. https://www.youtube.com/watch?v=ZMaZH3YYJqY


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