Warn on undefined loop exit.
2014-11-20 Andrew Stubbs <ams@codesourcery.com> gcc/ * tree-ssa-loop-niter.c (maybe_lower_iteration_bound): Warn if a loop condition would be removed due to undefined behaviour. gcc/testsuite/ * gcc.dg/undefined-loop-1.c: New file. * gcc.dg/undefined-loop-2.c: New file. From-SVN: r217891
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@ -1,3 +1,8 @@
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2014-11-20 Andrew Stubbs <ams@codesourcery.com>
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* tree-ssa-loop-niter.c (maybe_lower_iteration_bound): Warn if a loop
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condition would be removed due to undefined behaviour.
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2014-11-20 Andrew Pinski <apinski@cavium.com>
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PR ipa/63981
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@ -1,3 +1,8 @@
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2014-11-20 Andrew Stubbs <ams@codesourcery.com>
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* gcc.dg/undefined-loop-1.c: New file.
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* gcc.dg/undefined-loop-2.c: New file.
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2014-11-20 Tejas Belagod <tejas.belagod@arm.com>
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* gcc.target/aarch64/symbol-range.c: New.
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@ -0,0 +1,18 @@
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/* Check that loops whose final iteration is undefined are detected. */
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/* { dg-do compile } */
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/* { dg-options "-O2 -Waggressive-loop-optimizations" } */
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void doSomething(char);
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char array[5];
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void
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foo (void)
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{
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int i;
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for (i = 0;
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array[i] /* { dg-message "note: possible undefined statement is here" } */
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&& i < 5; /* { dg-warning "loop exit may only be reached after undefined behavior" } */
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i++)
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doSomething(array[i]);
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}
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@ -0,0 +1,22 @@
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/* Check that loops whose final iteration is undefined are detected. */
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/* { dg-do compile } */
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/* { dg-options "-O2 -Waggressive-loop-optimizations" } */
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void doSomething(char);
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char array1[5];
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char array2[5];
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void
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foo (int p)
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{
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int i;
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for (i=0;
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(p
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? array1[i] /* { dg-message "note: possible undefined statement is here" } */
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: array2[i]) /* { dg-message "note: possible undefined statement is here" } */
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&& i < 5 /* { dg-warning "loop exit may only be reached after undefined behavior" } */
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&& i < 100; /* { dg-warning "loop exit may only be reached after undefined behavior" } */
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i++)
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doSomething(array1[i]);
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}
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@ -3294,6 +3294,7 @@ maybe_lower_iteration_bound (struct loop *loop)
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struct nb_iter_bound *elt;
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bool found_exit = false;
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vec<basic_block> queue = vNULL;
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vec<gimple> problem_stmts = vNULL;
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bitmap visited;
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/* Collect all statements with interesting (i.e. lower than
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@ -3339,6 +3340,7 @@ maybe_lower_iteration_bound (struct loop *loop)
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if (not_executed_last_iteration->contains (stmt))
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{
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stmt_found = true;
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problem_stmts.safe_push (stmt);
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break;
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}
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if (gimple_has_side_effects (stmt))
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@ -3382,9 +3384,53 @@ maybe_lower_iteration_bound (struct loop *loop)
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"undefined statement must be executed at the last iteration.\n");
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record_niter_bound (loop, loop->nb_iterations_upper_bound - 1,
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false, true);
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if (warn_aggressive_loop_optimizations)
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{
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bool exit_warned = false;
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for (elt = loop->bounds; elt; elt = elt->next)
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{
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if (elt->is_exit
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&& wi::gtu_p (elt->bound, loop->nb_iterations_upper_bound))
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{
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basic_block bb = gimple_bb (elt->stmt);
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edge exit_edge = EDGE_SUCC (bb, 0);
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struct tree_niter_desc niter;
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if (!loop_exit_edge_p (loop, exit_edge))
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exit_edge = EDGE_SUCC (bb, 1);
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if(number_of_iterations_exit (loop, exit_edge,
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&niter, false, false)
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&& integer_onep (niter.assumptions)
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&& integer_zerop (niter.may_be_zero)
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&& niter.niter
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&& TREE_CODE (niter.niter) == INTEGER_CST
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&& wi::ltu_p (loop->nb_iterations_upper_bound,
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wi::to_widest (niter.niter)))
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{
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if (warning_at (gimple_location (elt->stmt),
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OPT_Waggressive_loop_optimizations,
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"loop exit may only be reached after undefined behavior"))
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exit_warned = true;
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}
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}
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}
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if (exit_warned && !problem_stmts.empty ())
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{
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gimple stmt;
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int index;
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FOR_EACH_VEC_ELT (problem_stmts, index, stmt)
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inform (gimple_location (stmt),
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"possible undefined statement is here");
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}
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}
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}
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BITMAP_FREE (visited);
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queue.release ();
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problem_stmts.release ();
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delete not_executed_last_iteration;
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}
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