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This patch adds logic to deal with the following constructions: %iv = phi i64 ... %trunc = trunc i64 %iv to i32 %cmp = icmp <pred> i32 %trunc, %invariant Replacing it with %iv = phi i64 ... %cmp = icmp <pred> i64 %iv, sext/zext(%invariant) In case if it is legal. Specifically, if `%iv` has signed comparison users, it is required that `sext(trunc(%iv)) == %iv`, and if it has unsigned comparison uses then we require `zext(trunc(%iv)) == %iv`. The current implementation bails if `%trunc` has other uses than `icmp`, but in theory we can handle more cases here (e.g. if the user of trunc is bitcast). Differential Revision: https://reviews.llvm.org/D47928 Reviewed By: reames llvm-svn: 335020
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