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re PR middle-end/64491 (incorrect warning: loop exit may only be reached after undefined behavior) 

Fix PR64491

2015-03-18  Andrew Stubbs  <ams@codesourcery.com>

	PR middle-end/64491
	Revert:
	2014-11-20  Andrew Stubbs  <ams@codesourcery.com>

	* tree-ssa-loop-niter.c (maybe_lower_iteration_bound): Warn if a loop
	condition would be removed due to undefined behaviour.

2015-03-18  Andrew Stubbs  <ams@codesourcery.com>

	PR middle-end/64491
	Revert:
	2014-11-20  Andrew Stubbs  <ams@codesourcery.com>

	* gcc.dg/undefined-loop-1.c: New file.
	* gcc.dg/undefined-loop-2.c: New file.

	2014-12-24  Andrew Stubbs  <ams@codesourcery.com>

	PR testsuite/64032
	* gcc.dg/undefined-loop-2.c: Don't allow GCC to optimize away the
	loop exits too early.

From-SVN: r221492
This commit is contained in:
Andrew Stubbs 2015-03-18 14:27:13 +00:00 committed by Andrew Stubbs
parent 1aec2ecce4
commit b4f3051a5f
5 changed files with 24 additions and 88 deletions
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9
gcc/ChangeLog
View File

@ -1,3 +1,12 @@
2015-03-18 Andrew Stubbs <ams@codesourcery.com>
PR middle-end/64491
Revert:
2014-11-20 Andrew Stubbs <ams@codesourcery.com>
* tree-ssa-loop-niter.c (maybe_lower_iteration_bound): Warn if a loop
condition would be removed due to undefined behaviour.
2015-03-18 Martin Liska <mliska@suse.cz>
PR ipa/65432

15
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,18 @@
2015-03-18 Andrew Stubbs <ams@codesourcery.com>
PR middle-end/64491
Revert:
2014-11-20 Andrew Stubbs <ams@codesourcery.com>
* gcc.dg/undefined-loop-1.c: New file.
* gcc.dg/undefined-loop-2.c: New file.
2014-12-24 Andrew Stubbs <ams@codesourcery.com>
PR testsuite/64032
* gcc.dg/undefined-loop-2.c: Don't allow GCC to optimize away the
loop exits too early.
2015-03-18 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/65450

18
gcc/testsuite/gcc.dg/undefined-loop-1.c
View File

@ -1,18 +0,0 @@
/* Check that loops whose final iteration is undefined are detected. */
/* { dg-do compile } */
/* { dg-options "-O2 -Waggressive-loop-optimizations" } */
void doSomething(char);
char array[5];
void
foo (void)
{
int i;
for (i = 0;
array[i] /* { dg-message "note: possible undefined statement is here" } */
&& i < 5; /* { dg-warning "loop exit may only be reached after undefined behavior" } */
i++)
doSomething(array[i]);
}

25
gcc/testsuite/gcc.dg/undefined-loop-2.c
View File

@ -1,25 +0,0 @@
/* Check that loops whose final iteration is undefined are detected. */
/* { dg-do compile } */
/* { dg-options "-O2 -Waggressive-loop-optimizations" } */
void doSomething(char);
char array1[5];
char array2[5];
void
foo (int p)
{
int i;
for (i=0;
(p
? array1[i] /* { dg-message "note: possible undefined statement is here" } */
: array2[i]) /* { dg-message "note: possible undefined statement is here" } */
&& i < 100; /* { dg-warning "loop exit may only be reached after undefined behavior" } */
i++)
{
if (i >= 5) /* { dg-warning "loop exit may only be reached after undefined behavior" } */
break;
doSomething(array1[i]);
}
}

45
gcc/tree-ssa-loop-niter.c
View File

@ -3329,7 +3329,6 @@ maybe_lower_iteration_bound (struct loop *loop)
struct nb_iter_bound *elt;
bool found_exit = false;
vec<basic_block> queue = vNULL;
vec<gimple> problem_stmts = vNULL;
bitmap visited;
/* Collect all statements with interesting (i.e. lower than
@ -3375,7 +3374,6 @@ maybe_lower_iteration_bound (struct loop *loop)
if (not_executed_last_iteration->contains (stmt))
{
stmt_found = true;
problem_stmts.safe_push (stmt);
break;
}
if (gimple_has_side_effects (stmt))
@ -3419,53 +3417,10 @@ maybe_lower_iteration_bound (struct loop *loop)
"undefined statement must be executed at the last iteration.\n");
record_niter_bound (loop, loop->nb_iterations_upper_bound - 1,
false, true);
if (warn_aggressive_loop_optimizations)
{
bool exit_warned = false;
for (elt = loop->bounds; elt; elt = elt->next)
{
if (elt->is_exit
&& wi::gtu_p (elt->bound, loop->nb_iterations_upper_bound))
{
basic_block bb = gimple_bb (elt->stmt);
edge exit_edge = EDGE_SUCC (bb, 0);
struct tree_niter_desc niter;
if (!loop_exit_edge_p (loop, exit_edge))
exit_edge = EDGE_SUCC (bb, 1);
if(number_of_iterations_exit (loop, exit_edge,
&niter, false, false)
&& integer_onep (niter.assumptions)
&& integer_zerop (niter.may_be_zero)
&& niter.niter
&& TREE_CODE (niter.niter) == INTEGER_CST
&& wi::ltu_p (loop->nb_iterations_upper_bound,
wi::to_widest (niter.niter)))
{
if (warning_at (gimple_location (elt->stmt),
OPT_Waggressive_loop_optimizations,
"loop exit may only be reached after undefined behavior"))
exit_warned = true;
}
}
}
if (exit_warned && !problem_stmts.is_empty ())
{
gimple stmt;
int index;
FOR_EACH_VEC_ELT (problem_stmts, index, stmt)
inform (gimple_location (stmt),
"possible undefined statement is here");
}
}
}
BITMAP_FREE (visited);
queue.release ();
problem_stmts.release ();
delete not_executed_last_iteration;
}