From da64698159fe69b68f5264b54cebcb67c501b3cf Mon Sep 17 00:00:00 2001 From: Richard Biener Date: Mon, 11 Nov 2024 09:40:20 +0100 Subject: [PATCH] tree-optimization/117510 - fix guard hoisting validity check For the loop in the testcase we currently fail to hoist the guard check of the inner loop (m > 0) out of the outer loop because find_loop_guard checks all blocks of the outer loop for side-effects, including those that are skipped by the guard. This usually is harmless as the guard does not skip any blocks in the outer loop but in this case store-motion was applied to the inner loop and thus there's now a skipped store in the outer loop. The following properly skips blocks that are dominated by the entry to the skipped region. PR tree-optimization/117510 * tree-ssa-loop-unswitch.cc (find_loop_guard): Only check not skipped blocks for side-effects. * gcc.dg/vect/vect-outer-pr117510.c: New testcase. --- gcc/testsuite/gcc.dg/vect/vect-outer-pr117510.c | 13 +++++++++++++ gcc/tree-ssa-loop-unswitch.cc | 6 +++++- 2 files changed, 18 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/gcc.dg/vect/vect-outer-pr117510.c diff --git a/gcc/testsuite/gcc.dg/vect/vect-outer-pr117510.c b/gcc/testsuite/gcc.dg/vect/vect-outer-pr117510.c new file mode 100644 index 00000000000..e50b67ce040 --- /dev/null +++ b/gcc/testsuite/gcc.dg/vect/vect-outer-pr117510.c @@ -0,0 +1,13 @@ +/* { dg-do compile } */ +/* { dg-require-effective-target vect_double } */ +/* { dg-additional-options "-O3" } */ + +void f(int n, int m, double *a) +{ + a = __builtin_assume_aligned (a, __BIGGEST_ALIGNMENT__); + for (int i = 0; i < n; i++) + for (int j = 0; j < m; j++) + a[i] += 2*a[i] + j; +} + +/* { dg-final { scan-tree-dump "OUTER LOOP VECTORIZED" "vect" } } */ diff --git a/gcc/tree-ssa-loop-unswitch.cc b/gcc/tree-ssa-loop-unswitch.cc index 847f7ac739f..88516fdb0a1 100644 --- a/gcc/tree-ssa-loop-unswitch.cc +++ b/gcc/tree-ssa-loop-unswitch.cc @@ -1256,7 +1256,11 @@ find_loop_guard (class loop *loop, vec &dbg_to_reset) guard_edge = NULL; goto end; } - if (!empty_bb_without_guard_p (loop, bb, dbg_to_reset)) + /* If any of the not skipped blocks has side-effects or defs with + uses outside of the loop we cannot hoist the guard. */ + if (!dominated_by_p (CDI_DOMINATORS, + bb, guard_edge == te ? fe->dest : te->dest) + && !empty_bb_without_guard_p (loop, bb, dbg_to_reset)) { if (dump_enabled_p ()) dump_printf_loc (MSG_MISSED_OPTIMIZATION, loc,