(Previous message: https://gcc.gnu.org/ml/gcc-patches/2015-12/msg02159.html) On Sat, Dec 26, 2015 at 18:58 PM, Richard Biener <richard.guent...@gmail.com> wrote:
>> I'm not sure whether adding a pass_copy_prop is the right thing here, but >> since >> loop-header-copying can create such opportunities, it seems good to take >> them! > > Aww. I'd rather have general infrastructure (like SCEV) deal with > those non-propagated copies. > > There are likely other missed propagation / folding opportunities > caused from partial peeling. > > Richard. I take your second point, but I am concerned that this leads to duplication of copy-propagation code throughout the compiler? However, this patch does that. Making analyze_initial_condition (alone) follow copies, is enough to solve my case of missed vectorization of pr65947-2.c; but I also used the routine in analyze_scalar_evolution_1, as it found copies to follow in both bootstrap and a significant number of testcases: c-c++-common/gomp/pr58472.c gcc.c-torture/execute/20000422-1.c gcc.c-torture/execute/20041213-2.c gcc.c-torture/execute/20100430-1.c gcc.c-torture/execute/pr49712.c gcc.c-torture/execute/pr58640.c gcc.dg/Warray-bounds-13.c gcc.dg/graphite/block-{1,5,6}.c gcc.dg/graphite/interchange-12.c gcc.dg/graphite/interchange-mvt.c gcc.dg/graphite/pr19910.c gcc.dg/graphite/uns-block-1.c gcc.dg/loop-unswitch-{2,4}.c gcc.dg/pr59670.c gcc.dg/torture/matrix-{1,2,3,4,5,6}.c gcc.dg/torture/pr24750-1.c gcc.dg/torture/transpose-{1,2,3,4,5,6}.c ...some of which were resolved to constants. (Of course, this approach is not as thorough as adding a pass_copy_prop. E.g. it does *not* enable vectorization of the inlined copy in pr65947-9.c.) Bootstrapped + check-gcc + check-g++ on ARM, AArch64, x86_64. gcc/ChangeLog: * tree-scalar-evolution.c (follow_copies): New. (analyze_initial_condition, analyze_scalar_evolution_1): Call previous. --- gcc/tree-scalar-evolution.c | 53 ++++++++++++++++++++++++++++++--------------- 1 file changed, 36 insertions(+), 17 deletions(-) diff --git a/gcc/tree-scalar-evolution.c b/gcc/tree-scalar-evolution.c index 9b33693..357eb8f 100644 --- a/gcc/tree-scalar-evolution.c +++ b/gcc/tree-scalar-evolution.c @@ -1522,6 +1522,37 @@ analyze_evolution_in_loop (gphi *loop_phi_node, return evolution_function; } +/* While VAR is an SSA_NAME whose definition is a straight copy of another name, + or (perhaps via a degenerate phi) a constant, follows that definition. + Returns the constant, or the earliest SSA_NAME whose definition is neither + constant nor copy. */ + +static tree +follow_copies (tree var) +{ + while (TREE_CODE (var) == SSA_NAME) + { + gimple *def = SSA_NAME_DEF_STMT (var); + if (gphi *phi = dyn_cast <gphi *> (def)) + { + tree rhs = degenerate_phi_result (phi); + /* Don't follow degenerate phi's of SSA_NAMES, that can break + loop-closed SSA form. */ + if (rhs && is_gimple_min_invariant (rhs)) + var = rhs; + break; + } + else if (gimple_assign_single_p (def) + && !gimple_vuse (def) + && (gimple_assign_rhs_code (def) == SSA_NAME + || is_gimple_min_invariant (gimple_assign_rhs1 (def)))) + var = gimple_assign_rhs1 (def); + else + break; + } + return var; +} + /* Given a loop-phi-node, return the initial conditions of the variable on entry of the loop. When the CCP has propagated constants into the loop-phi-node, the initial condition is @@ -1574,21 +1605,9 @@ analyze_initial_condition (gphi *loop_phi_node) if (init_cond == chrec_not_analyzed_yet) init_cond = chrec_dont_know; - /* During early loop unrolling we do not have fully constant propagated IL. - Handle degenerate PHIs here to not miss important unrollings. */ - if (TREE_CODE (init_cond) == SSA_NAME) - { - gimple *def = SSA_NAME_DEF_STMT (init_cond); - if (gphi *phi = dyn_cast <gphi *> (def)) - { - tree res = degenerate_phi_result (phi); - if (res != NULL_TREE - /* Only allow invariants here, otherwise we may break - loop-closed SSA form. */ - && is_gimple_min_invariant (res)) - init_cond = res; - } - } + /* We may not have fully constant propagated IL. Handle degenerate PHIs here + to not miss important early loop unrollings. */ + init_cond = follow_copies (init_cond); if (dump_file && (dump_flags & TDF_SCEV)) { @@ -1968,8 +1987,8 @@ analyze_scalar_evolution_1 (struct loop *loop, tree var, tree res) if (bb == NULL || !flow_bb_inside_loop_p (loop, bb)) { - /* Keep the symbolic form. */ - res = var; + /* Keep symbolic form, but look through obvious copies for constants. */ + res = follow_copies (var); goto set_and_end; } -- 1.9.1