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re PR tree-optimization/54985 (dom optimization erroneous remove conditional goto.) 

PR tree-optimization/54985
        * tree-ssa-threadedge.c (cond_arg_set_in_bb): New function extracted
        from thread_across_edge.
        (thread_across_edge): Use it in all cases where we might thread
        across a back edge.

        * gcc.c-torture/execute/pr54985.c: New test.

From-SVN: r193108
This commit is contained in:
Jeff Law 2012-11-02 14:19:16 -06:00 committed by Jeff Law
parent e54acbedb8
commit e8b6f29ec1
4 changed files with 101 additions and 19 deletions
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8
gcc/ChangeLog
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@ -1,3 +1,11 @@
2012-11-02 Jeff Law <law@redhat.com>
PR tree-optimization/54985
* tree-ssa-threadedge.c (cond_arg_set_in_bb): New function extracted
from thread_across_edge.
(thread_across_edge): Use it in all cases where we might thread
across a back edge.
2012-10-31 Eric Botcazou <ebotcazou@adacore.com>
* config/i386/i386.c (ix86_expand_prologue): Emit frame info for the

4
gcc/testsuite/ChangeLog
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@ -1,3 +1,7 @@
2012-11-02 Jeff Law <law@redhat.com>
* gcc.c-torture/execute/pr54985.c: New test.
2012-10-29 Eric Botcazou <ebotcazou@adacore.com>
PR ada/53517

36
gcc/testsuite/gcc.c-torture/execute/pr54985.c Normal file
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@ -0,0 +1,36 @@
typedef struct st {
int a;
} ST;
int __attribute__((noinline,noclone))
foo(ST *s, int c)
{
int first = 1;
int count = c;
ST *item = s;
int a = s->a;
int x;
while (count--)
{
x = item->a;
if (first)
first = 0;
else if (x >= a)
return 1;
a = x;
item++;
}
return 0;
}
extern void abort (void);
int main ()
{
ST _1[2] = {{2}, {1}};
if (foo(_1, 2) != 0)
abort ();
return 0;
}

72
gcc/tree-ssa-threadedge.c
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@ -574,6 +574,44 @@ simplify_control_stmt_condition (edge e,
return cached_lhs;
}
/* Return TRUE if the statement at the end of e->dest depends on
the output of any statement in BB. Otherwise return FALSE.
This is used when we are threading a backedge and need to ensure
that temporary equivalences from BB do not affect the condition
in e->dest. */
static bool
cond_arg_set_in_bb (edge e, basic_block bb)
{
ssa_op_iter iter;
use_operand_p use_p;
gimple last = last_stmt (e->dest);
/* E->dest does not have to end with a control transferring
instruction. This can occurr when we try to extend a jump
threading opportunity deeper into the CFG. In that case
it is safe for this check to return false. */
if (!last)
return false;
if (gimple_code (last) != GIMPLE_COND
&& gimple_code (last) != GIMPLE_GOTO
&& gimple_code (last) != GIMPLE_SWITCH)
return false;
FOR_EACH_SSA_USE_OPERAND (use_p, last, iter, SSA_OP_USE | SSA_OP_VUSE)
{
tree use = USE_FROM_PTR (use_p);
if (TREE_CODE (use) == SSA_NAME
&& gimple_code (SSA_NAME_DEF_STMT (use)) != GIMPLE_PHI
&& gimple_bb (SSA_NAME_DEF_STMT (use)) == bb)
return true;
}
return false;
}
/* TAKEN_EDGE represents the an edge taken as a result of jump threading.
See if we can thread around TAKEN_EDGE->dest as well. If so, return
the edge out of TAKEN_EDGE->dest that we can statically compute will be
@ -707,19 +745,8 @@ thread_across_edge (gimple dummy_cond,
safe to thread this edge. */
if (e->flags & EDGE_DFS_BACK)
{
ssa_op_iter iter;
use_operand_p use_p;
gimple last = gsi_stmt (gsi_last_bb (e->dest));
FOR_EACH_SSA_USE_OPERAND (use_p, last, iter, SSA_OP_USE | SSA_OP_VUSE)
{
tree use = USE_FROM_PTR (use_p);
if (TREE_CODE (use) == SSA_NAME
&& gimple_code (SSA_NAME_DEF_STMT (use)) != GIMPLE_PHI
&& gimple_bb (SSA_NAME_DEF_STMT (use)) == e->dest)
goto fail;
}
if (cond_arg_set_in_bb (e, e->dest))
goto fail;
}
stmt_count = 0;
@ -760,7 +787,9 @@ thread_across_edge (gimple dummy_cond,
address. If DEST is not null, then see if we can thread
through it as well, this helps capture secondary effects
of threading without having to re-run DOM or VRP. */
if (dest)
if (dest
&& ((e->flags & EDGE_DFS_BACK) == 0
|| ! cond_arg_set_in_bb (taken_edge, e->dest)))
{
/* We don't want to thread back to a block we have already
visited. This may be overly conservative. */
@ -818,11 +847,16 @@ thread_across_edge (gimple dummy_cond,
e3 = taken_edge;
do
{
e2 = thread_around_empty_block (e3,
dummy_cond,
handle_dominating_asserts,
simplify,
visited);
if ((e->flags & EDGE_DFS_BACK) == 0
|| ! cond_arg_set_in_bb (e3, e->dest))
e2 = thread_around_empty_block (e3,
dummy_cond,
handle_dominating_asserts,
simplify,
visited);
else
e2 = NULL;
if (e2)
{
e3 = e2;