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re PR middle-end/55481 (-O2 generates a wrong-code infinite loop in C++Benchmark's simple_types_constant_folding int8 xor test) 

2012-12-12  Zdenek Dvorak  <ook@ucw.cz>

	PR tree-optimization/55481
	* tree-ssa-loop-ivopts.c (rewrite_use_nonlinear_expr): Fall
	back to general rewriting if we cannot leave an original biv
	definition alone.

	* gcc.dg/torture/pr55481.c: New testcase.

From-SVN: r194444
This commit is contained in:
Zdenek Dvorak 2012-12-12 14:07:19 +01:00 committed by Richard Biener
parent 85619b6fc1
commit d06a01bf68
4 changed files with 38 additions and 32 deletions
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7
gcc/ChangeLog
View File

@ -1,3 +1,10 @@
2012-12-12 Zdenek Dvorak <ook@ucw.cz>
PR tree-optimization/55481
* tree-ssa-loop-ivopts.c (rewrite_use_nonlinear_expr): Fall
back to general rewriting if we cannot leave an original biv
definition alone.
2012-12-12 Jakub Jelinek <jakub@redhat.com>
PR target/55659

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2012-12-12 Zdenek Dvorak <ook@ucw.cz>
PR tree-optimization/55481
* gcc.dg/torture/pr55481.c: New testcase.
2012-12-12 Steven Bosscher <steven@gcc.gnu.org>
Jakub Jelinek <jakub@redhat.com>

16
gcc/testsuite/gcc.dg/torture/pr55481.c Normal file
View File

@ -0,0 +1,16 @@
/* { dg-do run } */
int main()
{
signed char result = 0;
int n;
for (n = 0; n < 13; ++n)
{
int tem = result;
tem = tem + 31;
result = tem;
}
if (result != -109)
__builtin_abort ();
return 0;
}

42
gcc/tree-ssa-loop-ivopts.c
View File

@ -6088,35 +6088,24 @@ rewrite_use_nonlinear_expr (struct ivopts_data *data,
if (cand->pos == IP_ORIGINAL
&& cand->incremented_at == use->stmt)
{
tree step, ctype, utype;
enum tree_code incr_code = PLUS_EXPR, old_code;
enum tree_code stmt_code;
gcc_assert (is_gimple_assign (use->stmt));
gcc_assert (gimple_assign_lhs (use->stmt) == cand->var_after);
step = cand->iv->step;
ctype = TREE_TYPE (step);
utype = TREE_TYPE (cand->var_after);
if (TREE_CODE (step) == NEGATE_EXPR)
{
incr_code = MINUS_EXPR;
step = TREE_OPERAND (step, 0);
}
/* Check whether we may leave the computation unchanged.
This is the case only if it does not rely on other
computations in the loop -- otherwise, the computation
we rely upon may be removed in remove_unused_ivs,
thus leading to ICE. */
old_code = gimple_assign_rhs_code (use->stmt);
if (old_code == PLUS_EXPR
|| old_code == MINUS_EXPR
|| old_code == POINTER_PLUS_EXPR)
stmt_code = gimple_assign_rhs_code (use->stmt);
if (stmt_code == PLUS_EXPR
|| stmt_code == MINUS_EXPR
|| stmt_code == POINTER_PLUS_EXPR)
{
if (gimple_assign_rhs1 (use->stmt) == cand->var_before)
op = gimple_assign_rhs2 (use->stmt);
else if (old_code != MINUS_EXPR
&& gimple_assign_rhs2 (use->stmt) == cand->var_before)
else if (gimple_assign_rhs2 (use->stmt) == cand->var_before)
op = gimple_assign_rhs1 (use->stmt);
else
op = NULL_TREE;
@ -6124,23 +6113,12 @@ rewrite_use_nonlinear_expr (struct ivopts_data *data,
else
op = NULL_TREE;
if (op
&& (TREE_CODE (op) == INTEGER_CST
|| operand_equal_p (op, step, 0)))
if (op && expr_invariant_in_loop_p (data->current_loop, op))
return;
}
/* Otherwise, add the necessary computations to express
the iv. */
op = fold_convert (ctype, cand->var_before);
comp = fold_convert (utype,
build2 (incr_code, ctype, op,
unshare_expr (step)));
}
else
{
comp = get_computation (data->current_loop, use, cand);
gcc_assert (comp != NULL_TREE);
}
comp = get_computation (data->current_loop, use, cand);
gcc_assert (comp != NULL_TREE);
switch (gimple_code (use->stmt))
{