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tree-optimization/117574 - bougs niter lt-to-ne

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When trying to change a IV from IV0 < IV1 to IV0' != IV1' we apply
fancy adjustments to the may_be_zero condition we compute rather
than using the obvious IV0->base >= IV1->base expression (to be
able to use > instead of >=?).  This doesn't seem to go well.

	PR tree-optimization/117574
	* tree-ssa-loop-niter.cc (number_of_iterations_lt_to_ne):
	Use the obvious may_be_zero condition.

	* gcc.dg/torture/pr117574-1.c: New testcase.
This commit is contained in:
Richard Biener 2024-11-15 11:56:14 +01:00 committed by Richard Biener
parent ed6d0867fd
commit ff5a14abeb
2 changed files with 27 additions and 24 deletions
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20
gcc/testsuite/gcc.dg/torture/pr117574-1.c Normal file
View File

@ -0,0 +1,20 @@
/* { dg-do run } */
void abort (void);
int a, c;
long b;
short d;
static long e(long f, long h, long i) {
for (long g = f; g <= h; g += i)
b += g;
return b;
}
int main() {
c = 1;
for (; c >= 0; c--)
;
for (; e(d + 40, d + 76, c + 51) < 4;)
;
if (a != 0)
abort ();
}

31
gcc/tree-ssa-loop-niter.cc
View File

@ -1200,17 +1200,6 @@ number_of_iterations_lt_to_ne (tree type, affine_iv *iv0, affine_iv *iv1,
if (integer_zerop (assumption))
return false;
}
if (mpz_cmp (mmod, bnds->below) < 0)
noloop = boolean_false_node;
else if (POINTER_TYPE_P (type))
noloop = fold_build2 (GT_EXPR, boolean_type_node,
iv0->base,
fold_build_pointer_plus (iv1->base, tmod));
else
noloop = fold_build2 (GT_EXPR, boolean_type_node,
iv0->base,
fold_build2 (PLUS_EXPR, type1,
iv1->base, tmod));
}
else
{
@ -1226,21 +1215,15 @@ number_of_iterations_lt_to_ne (tree type, affine_iv *iv0, affine_iv *iv1,
if (integer_zerop (assumption))
return false;
}
if (mpz_cmp (mmod, bnds->below) < 0)
noloop = boolean_false_node;
else if (POINTER_TYPE_P (type))
noloop = fold_build2 (GT_EXPR, boolean_type_node,
fold_build_pointer_plus (iv0->base,
fold_build1 (NEGATE_EXPR,
type1, tmod)),
iv1->base);
else
noloop = fold_build2 (GT_EXPR, boolean_type_node,
fold_build2 (MINUS_EXPR, type1,
iv0->base, tmod),
iv1->base);
}
/* IV0 < IV1 does not loop if IV0->base >= IV1->base. */
if (mpz_cmp (mmod, bnds->below) < 0)
noloop = boolean_false_node;
else
noloop = fold_build2 (GE_EXPR, boolean_type_node,
iv0->base, iv1->base);
if (!integer_nonzerop (assumption))
niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
niter->assumptions,