[PATCH] D75982: [DAGCombine] Respect the uses when combine FMA for a*b+/-c*d and add target hook if there uses are the same
Roman Lebedev via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Wed Mar 11 06:18:08 PDT 2020
lebedev.ri added reviewers: cameron.mcinally, uweigand.
lebedev.ri added a comment.
> If their uses are the same, add a target hook to allow some platform such as PowerPC to make the choice, as it has different precisions between these two folding which is caused by round a*b or c*d.
> In PowerPC, we have some floating precision quite sensitive libraries that depend on the slightly difference between rounding a*b or c*d. So, we need some way to control the behavior of this combine.
To me that sounds like strict floating point semantics should be used there?
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https://reviews.llvm.org/D75982/new/
https://reviews.llvm.org/D75982
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