This patch folds certain reductions of X & CST to X[I] & CST[I] if I is
the only nonzero element of CST. This includes the motivating case in
which CST[I] is -1.
We could do the same for REDUC_MAX on unsigned types, but I wasn't sure
that that special case was worth it.
2019-01-07 Richard Sandiford <richard.sandiford@arm.com>
gcc/
PR tree-optimization/88598
* tree.h (single_nonzero_element): Declare.
* tree.c (single_nonzero_element): New function.
* match.pd: Fold certain reductions of X & CST to X[I] & CST[I]
if I is the only nonzero element of CST.