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re PR tree-optimization/72817 (wrong code at -O3 on x86_64-linux-gnu (in both 32-bit and 64-bit modes)) 

PR tree-optimization/72817
	PR tree-optimization/73450
	* tree-ssa-loop-niter.c (number_of_iterations_ne): Check
	multiple_of_p for adjusted IV.base.

	gcc/testsuite
	* gcc.dg/tree-ssa/pr72817.c: New test.
	* gcc.dg/tree-ssa/pr73450.c: New test.

From-SVN: r239494
This commit is contained in:
Bin Cheng 2016-08-16 09:13:50 +00:00 committed by Bin Cheng
parent f6ba953d24
commit 8f21990a67
5 changed files with 72 additions and 20 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2016-08-16 Bin Cheng <bin.cheng@arm.com>
PR tree-optimization/72817
PR tree-optimization/73450
* tree-ssa-loop-niter.c (number_of_iterations_ne): Check
multiple_of_p for adjusted IV.base.
2016-08-15 Uros Bizjak <ubizjak@gmail.com>
PR target/72867

7
gcc/testsuite/ChangeLog
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@ -1,3 +1,10 @@
2016-08-16 Bin Cheng <bin.cheng@arm.com>
PR tree-optimization/72817
PR tree-optimization/73450
* gcc.dg/tree-ssa/pr72817.c: New test.
* gcc.dg/tree-ssa/pr73450.c: New test.
2016-08-15 Fritz Reese <fritzoreese@gmail.com>
* gfortran.dg/init_flag_13.f90: New testcase.

13
gcc/testsuite/gcc.dg/tree-ssa/pr72817.c Normal file
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@ -0,0 +1,13 @@
/* { dg-do run } */
/* { dg-options "-O3" } */
char a;
short b;
int main ()
{
for (a = 3; a != -1; a -= 5)
while (b)
;
return 0;
}

14
gcc/testsuite/gcc.dg/tree-ssa/pr73450.c Normal file
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@ -0,0 +1,14 @@
/* { dg-do run } */
/* { dg-options "-O3" } */
int a;
char b;
int main() {
char c = 0;
for (; c != 3; c = c + 7) {
a = b & a;
if (a)
break;
}
return 0;
}

51
gcc/tree-ssa-loop-niter.c
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@ -999,33 +999,36 @@ number_of_iterations_ne (struct loop *loop, tree type, affine_iv *iv,
mpz_clear (max);
/* Compute no-overflow information for the control iv. This can be
proven when below two conditions hold.
1) |FINAL - base| is an exact multiple of step.
2) IV evaluates toward FINAL at beginning, i.e:
proven when below two conditions are satisfied:
1) IV evaluates toward FINAL at beginning, i.e:
base <= FINAL ; step > 0
base >= FINAL ; step < 0
Note the first condition holds, the second can be then relaxed
to below condition.
2) |FINAL - base| is an exact multiple of step.
base - step < FINAL ; step > 0
&& base - step doesn't underflow
base - step > FINAL ; step < 0
&& base - step doesn't overflow
Unfortunately, it's hard to prove above conditions after pass loop-ch
because loop with exit condition (IV != FINAL) usually will be guarded
by initial-condition (IV.base - IV.step != FINAL). In this case, we
can alternatively try to prove below conditions:
The relaxation is important because after pass loop-ch, loop
with exit condition (IV != FINAL) will usually be guarded by
pre-condition (IV.base - IV.step != FINAL). Please refer to
PR34114 as an example.
1') IV evaluates toward FINAL at beginning, i.e:
new_base = base - step < FINAL ; step > 0
&& base - step doesn't underflow
new_base = base - step > FINAL ; step < 0
&& base - step doesn't overflow
Also note, for NE_EXPR, base equals to FINAL is a special case, in
2') |FINAL - new_base| is an exact multiple of step.
Please refer to PR34114 as an example of loop-ch's impact, also refer
to PR72817 as an example why condition 2') is necessary.
Note, for NE_EXPR, base equals to FINAL is a special case, in
which the loop exits immediately, and the iv does not overflow. */
if (!niter->control.no_overflow
&& (integer_onep (s) || multiple_of_p (type, c, s)))
{
tree t, cond, relaxed_cond = boolean_false_node;
tree t, cond, new_c, relaxed_cond = boolean_false_node;
if (tree_int_cst_sign_bit (iv->step))
{
@ -1039,8 +1042,12 @@ number_of_iterations_ne (struct loop *loop, tree type, affine_iv *iv,
if (integer_nonzerop (t))
{
t = fold_build2 (MINUS_EXPR, type, iv->base, iv->step);
relaxed_cond = fold_build2 (GT_EXPR, boolean_type_node,
t, final);
new_c = fold_build2 (MINUS_EXPR, niter_type,
fold_convert (niter_type, t),
fold_convert (niter_type, final));
if (multiple_of_p (type, new_c, s))
relaxed_cond = fold_build2 (GT_EXPR, boolean_type_node,
t, final);
}
}
}
@ -1056,8 +1063,12 @@ number_of_iterations_ne (struct loop *loop, tree type, affine_iv *iv,
if (integer_nonzerop (t))
{
t = fold_build2 (MINUS_EXPR, type, iv->base, iv->step);
relaxed_cond = fold_build2 (LT_EXPR, boolean_type_node,
t, final);
new_c = fold_build2 (MINUS_EXPR, niter_type,
fold_convert (niter_type, final),
fold_convert (niter_type, t));
if (multiple_of_p (type, new_c, s))
relaxed_cond = fold_build2 (LT_EXPR, boolean_type_node,
t, final);
}
}
}