Richard Biener <richard.guent...@gmail.com> writes: > On Tue, Nov 5, 2019 at 3:25 PM Richard Sandiford > <richard.sandif...@arm.com> wrote: >> >> This patch makes two tweaks to vectorizable_conversion. The first >> is to use "modifier" to distinguish between promotion, demotion, >> and neither promotion nor demotion, rather than using a code for >> some cases and "modifier" for others. The second is to take ncopies >> into account for the promotion and demotion costs; previously we gave >> multiple copies the same cost as a single copy. >> >> Later patches test this, but it seemed worth splitting out. > > OK, but does ncopies properly handle unrolling with SLP?
Bah, thanks for catching that. Here's a fixed version, tested as before. Richard 2019-11-07 Richard Sandiford <richard.sandif...@arm.com> gcc/ * tree-vect-stmts.c (vect_model_promotion_demotion_cost): Take the number of ncopies as an additional argument. (vectorizable_conversion): Update call accordingly. Use "modifier" to check whether a conversion is between vectors with the same numbers of units. Index: gcc/tree-vect-stmts.c =================================================================== --- gcc/tree-vect-stmts.c 2019-11-07 15:11:49.000000000 +0000 +++ gcc/tree-vect-stmts.c 2019-11-07 15:11:50.134775028 +0000 @@ -917,26 +917,27 @@ vect_model_simple_cost (stmt_vec_info st } -/* Model cost for type demotion and promotion operations. PWR is normally - zero for single-step promotions and demotions. It will be one if - two-step promotion/demotion is required, and so on. Each additional +/* Model cost for type demotion and promotion operations. PWR is + normally zero for single-step promotions and demotions. It will be + one if two-step promotion/demotion is required, and so on. NCOPIES + is the number of vector results (and thus number of instructions) + for the narrowest end of the operation chain. Each additional step doubles the number of instructions required. */ static void vect_model_promotion_demotion_cost (stmt_vec_info stmt_info, - enum vect_def_type *dt, int pwr, + enum vect_def_type *dt, + unsigned int ncopies, int pwr, stmt_vector_for_cost *cost_vec) { - int i, tmp; + int i; int inside_cost = 0, prologue_cost = 0; for (i = 0; i < pwr + 1; i++) { - tmp = (STMT_VINFO_TYPE (stmt_info) == type_promotion_vec_info_type) ? - (i + 1) : i; - inside_cost += record_stmt_cost (cost_vec, vect_pow2 (tmp), - vec_promote_demote, stmt_info, 0, - vect_body); + inside_cost += record_stmt_cost (cost_vec, ncopies, vec_promote_demote, + stmt_info, 0, vect_body); + ncopies *= 2; } /* FORNOW: Assuming maximum 2 args per stmts. */ @@ -4964,7 +4965,7 @@ vectorizable_conversion (stmt_vec_info s if (!vec_stmt) /* transformation not required. */ { DUMP_VECT_SCOPE ("vectorizable_conversion"); - if (code == FIX_TRUNC_EXPR || code == FLOAT_EXPR) + if (modifier == NONE) { STMT_VINFO_TYPE (stmt_info) = type_conversion_vec_info_type; vect_model_simple_cost (stmt_info, ncopies, dt, ndts, slp_node, @@ -4973,14 +4974,24 @@ vectorizable_conversion (stmt_vec_info s else if (modifier == NARROW) { STMT_VINFO_TYPE (stmt_info) = type_demotion_vec_info_type; - vect_model_promotion_demotion_cost (stmt_info, dt, multi_step_cvt, - cost_vec); + /* The final packing step produces one vector result per copy. */ + unsigned int nvectors + = (slp_node ? SLP_TREE_NUMBER_OF_VEC_STMTS (slp_node) : ncopies); + vect_model_promotion_demotion_cost (stmt_info, dt, nvectors, + multi_step_cvt, cost_vec); } else { STMT_VINFO_TYPE (stmt_info) = type_promotion_vec_info_type; - vect_model_promotion_demotion_cost (stmt_info, dt, multi_step_cvt, - cost_vec); + /* The initial unpacking step produces two vector results + per copy. MULTI_STEP_CVT is 0 for a single conversion, + so >> MULTI_STEP_CVT divides by 2^(number of steps - 1). */ + unsigned int nvectors + = (slp_node + ? SLP_TREE_NUMBER_OF_VEC_STMTS (slp_node) >> multi_step_cvt + : ncopies * 2); + vect_model_promotion_demotion_cost (stmt_info, dt, nvectors, + multi_step_cvt, cost_vec); } interm_types.release (); return true;