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Summary: Lift the restrictions that prevented the tree walking introduced in the previous change and add support for patterns like: (G_ADD (G_MUL (G_SEXT $src1), (G_SEXT $src2)), $src3) -> SMADDWrrr $dst, $src1, $src2, $src3 Also adds support for G_SEXT and G_ZEXT to support these cases. One particular aspect of this that I should draw attention to is that I've tried to be overly conservative in determining the safety of matches that involve non-adjacent instructions and multiple basic blocks. This is intended to be used as a cheap initial check and we may add a more expensive check in the future. The current rules are: * Reject if any instruction may load/store (we'd need to check for intervening memory operations. * Reject if any instruction has implicit operands. * Reject if any instruction has unmodelled side-effects. See isObviouslySafeToFold(). Reviewers: t.p.northover, javed.absar, qcolombet, aditya_nandakumar, ab, rovka Reviewed By: ab Subscribers: igorb, dberris, llvm-commits, kristof.beyls Differential Revision: https://reviews.llvm.org/D30539 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299430 91177308-0d34-0410-b5e6-96231b3b80d8