From 963aeaad25122bc507f9c72b9af6fc13cbeccde4 Mon Sep 17 00:00:00 2001 From: Richard Sandiford Date: Wed, 16 Aug 2017 07:51:13 +0000 Subject: [PATCH] PR81815: Invalid conditional reduction We weren't checking whether the phi in a conditional reduction was used by the condition itself (which isn't a case we handle). 2017-08-11 Richard Sandiford gcc/ PR tree-optimization/81835 * tree-vect-loop.c (vect_is_simple_reduction): Simply checks for the phi SSA_NAME. Check that the condition in a COND_EXPR does not depend on the phi. gcc/testsuite/ PR tree-optimization/81835 * gcc.dg/vect/pr81815.c: New test. From-SVN: r251117 --- gcc/ChangeLog | 7 +++++++ gcc/testsuite/ChangeLog | 5 +++++ gcc/testsuite/gcc.dg/vect/pr81815.c | 26 ++++++++++++++++++++++++++ gcc/tree-vect-loop.c | 19 ++++++++++++------- 4 files changed, 50 insertions(+), 7 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/vect/pr81815.c diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 14768398af8..d86b59f3671 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,10 @@ +2017-08-16 Richard Sandiford + + PR tree-optimization/81835 + * tree-vect-loop.c (vect_is_simple_reduction): Simply checks for + the phi SSA_NAME. Check that the condition in a COND_EXPR does + not depend on the phi. + 2017-08-16 Alan Modra * config/rs6000/rs6000.c (rs6000_init_hard_regno_mode_ok): Delete diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 835a8f4af81..fe2ea0221f8 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2017-08-16 Richard Sandiford + + PR tree-optimization/81835 + * gcc.dg/vect/pr81815.c: New test. + 2017-08-15 Joseph Myers PR target/78460 diff --git a/gcc/testsuite/gcc.dg/vect/pr81815.c b/gcc/testsuite/gcc.dg/vect/pr81815.c new file mode 100644 index 00000000000..1eb7c59b70e --- /dev/null +++ b/gcc/testsuite/gcc.dg/vect/pr81815.c @@ -0,0 +1,26 @@ +/* { dg-do run } */ + +int __attribute__ ((noinline, noclone)) +f (int *x, int n) +{ + int b = 13; + for (int i = 0; i < n; ++i) + { + int next = x[i]; + b = b < 100 ? next : 200; + } + return b; +} + +static int res[32]; + +int +main (void) +{ + for (int i = 0; i < 32; ++i) + res[i] = i; + res[15] = 100; + if (f (res, 32) != 200) + __builtin_abort (); + return 0; +} diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c index 8b2a61e733b..906323b4d76 100644 --- a/gcc/tree-vect-loop.c +++ b/gcc/tree-vect-loop.c @@ -2690,15 +2690,15 @@ vect_is_simple_reduction (loop_vec_info loop_info, gimple *phi, *double_reduc = false; *v_reduc_type = TREE_CODE_REDUCTION; - name = PHI_RESULT (phi); + tree phi_name = PHI_RESULT (phi); /* ??? If there are no uses of the PHI result the inner loop reduction won't be detected as possibly double-reduction by vectorizable_reduction because that tries to walk the PHI arg from the preheader edge which can be constant. See PR60382. */ - if (has_zero_uses (name)) + if (has_zero_uses (phi_name)) return NULL; nloop_uses = 0; - FOR_EACH_IMM_USE_FAST (use_p, imm_iter, name) + FOR_EACH_IMM_USE_FAST (use_p, imm_iter, phi_name) { gimple *use_stmt = USE_STMT (use_p); if (is_gimple_debug (use_stmt)) @@ -2847,10 +2847,7 @@ vect_is_simple_reduction (loop_vec_info loop_info, gimple *phi, simply rewriting this into "res += -x[i]". Avoid changing gimple instruction for the first simple tests and only do this if we're allowed to change code at all. */ - if (code == MINUS_EXPR - && ! ((op1 = gimple_assign_rhs2 (def_stmt)) - && TREE_CODE (op1) == SSA_NAME - && SSA_NAME_DEF_STMT (op1) == phi)) + if (code == MINUS_EXPR && gimple_assign_rhs2 (def_stmt) != phi_name) code = PLUS_EXPR; if (code == COND_EXPR) @@ -2864,6 +2861,14 @@ vect_is_simple_reduction (loop_vec_info loop_info, gimple *phi, op4 = TREE_OPERAND (op3, 1); op3 = TREE_OPERAND (op3, 0); } + if (op3 == phi_name || op4 == phi_name) + { + if (dump_enabled_p ()) + report_vect_op (MSG_MISSED_OPTIMIZATION, def_stmt, + "reduction: condition depends on previous" + " iteration: "); + return NULL; + } op1 = gimple_assign_rhs2 (def_stmt); op2 = gimple_assign_rhs3 (def_stmt); -- 2.30.2