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tree-optimization/104519 - adjust PR100499 niter fix

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The following adjusts the PR100499 niter fix to use the appropriate
types when checking whether the difference between the final and base
values of the IV are a multiple of the step.  It also gets rid of
an always false condition in multiple_of_p which lead me to a
wrong solution first.

2022-02-15  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/104519
	* fold-const.cc (multiple_of_p): Remove never true condition.
	* tree-ssa-loop-niter.cc (number_of_iterations_ne): Use
	the appropriate types for determining whether the difference
	of final and base is a multiple of the step.

	* gcc.dg/torture/pr104519.c: New testcase.
This commit is contained in:
Richard Biener 2022-02-15 09:40:59 +01:00
parent c4c0aa6089
commit d8b6da8dd1
3 changed files with 22 additions and 10 deletions
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6
gcc/fold-const.cc
View file

@ -14208,11 +14208,7 @@ multiple_of_p (tree type, const_tree top, const_tree bottom, bool nowrap)
&& multiple_of_p (type, TREE_OPERAND (top, 2), bottom, nowrap));
case INTEGER_CST:
if (TREE_CODE (bottom) != INTEGER_CST
|| integer_zerop (bottom)
|| (TYPE_UNSIGNED (type)
&& (tree_int_cst_sgn (top) < 0
|| tree_int_cst_sgn (bottom) < 0)))
if (TREE_CODE (bottom) != INTEGER_CST || integer_zerop (bottom))
return 0;
return wi::multiple_of_p (wi::to_widest (top), wi::to_widest (bottom),
SIGNED);

10
gcc/testsuite/gcc.dg/torture/pr104519.c Normal file
View file

@ -0,0 +1,10 @@
/* { dg-do run } */
signed char a, b;
int main()
{
for (b = -7; b; b += 3)
if (a)
__builtin_abort();
return 0;
}

16
gcc/tree-ssa-loop-niter.cc
View file

@ -1048,13 +1048,19 @@ number_of_iterations_ne (class loop *loop, tree type, affine_iv *iv,
which the loop exits immediately, and the iv does not overflow.
Also note, we prove condition 2) by checking base and final seperately
along with condition 1) or 1'). */
along with condition 1) or 1'). Since we ensure the difference
computation of c does not wrap with cond below and the adjusted s
will fit a signed type as well as an unsigned we can safely do
this using the type of the IV if it is not pointer typed. */
tree mtype = type;
if (POINTER_TYPE_P (type))
mtype = niter_type;
if (!niter->control.no_overflow
&& (integer_onep (s)
|| (multiple_of_p (type, fold_convert (niter_type, iv->base), s,
false)
&& multiple_of_p (type, fold_convert (niter_type, final), s,
false))))
|| (multiple_of_p (mtype, fold_convert (mtype, iv->base),
fold_convert (mtype, s), false)
&& multiple_of_p (mtype, fold_convert (mtype, final),
fold_convert (mtype, s), false))))
{
tree t, cond, relaxed_cond = boolean_false_node;