================
@@ -1523,6 +1523,34 @@ static Instruction *foldBoxMultiply(BinaryOperator &I) {
return nullptr;
}
+/// Canonicalize a nested add/sub with a constant on the inner RHS by
+/// sinking the constant to the outer RHS.
+/// (X +/- C) +/- Y -> (X +/- Y) +/- C
----------------
MaxGraey wrote:
Yeah, but as far as I know, Reassociate pass only works when the inner and
outer associative operations are the same. To avoid this conflict, we can stop
this reassociating in this case. It’s actually strange why this is done, since
simple binary canonization in LLVM (and not only here) is designed so that a
constant is always on the right-hand side; therefore, to simplify the constant
folding and reduce the number of isomorphic forms for matching, it makes sense
to push constants from the nested expression nodes in the same direction if
this possible.
https://github.com/llvm/llvm-project/pull/191022
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