As mentioned in https://gcc.gnu.org/ml/gcc-patches/2017-11/msg01575.html , the scatter handling in vectorizable_store seems to be dead code at the moment. Enabling it with the vect_analyze_data_ref_access part of that patch triggered an ICE in the avx512f-scatter-*.c tests (which previously didn't use scatters). The problem was that the NARROW and WIDEN handling uses permute_vec_elements to marshal the inputs, and permute_vec_elements expected the lhs of the stmt to be an SSA_NAME, which of course it isn't for stores.
This patch makes permute_vec_elements create a fresh variable in this case. Tested on x86_64-linux-gnu. OK to install? Richard 2018-01-09 Richard Sandiford <richard.sandif...@linaro.org> gcc/ * tree-vect-stmts.c (permute_vec_elements): Create a fresh variable if the destination isn't an SSA_NAME. Index: gcc/tree-vect-stmts.c =================================================================== --- gcc/tree-vect-stmts.c 2018-01-03 21:47:27.956862491 +0000 +++ gcc/tree-vect-stmts.c 2018-01-09 11:30:00.578821631 +0000 @@ -6585,7 +6585,11 @@ permute_vec_elements (tree x, tree y, tr tree perm_dest, data_ref; gimple *perm_stmt; - perm_dest = vect_create_destination_var (gimple_get_lhs (stmt), vectype); + tree scalar_dest = gimple_get_lhs (stmt); + if (TREE_CODE (scalar_dest) == SSA_NAME) + perm_dest = vect_create_destination_var (scalar_dest, vectype); + else + perm_dest = vect_get_new_vect_var (vectype, vect_simple_var, NULL); data_ref = make_ssa_name (perm_dest); /* Generate the permute statement. */