https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102087
--- Comment #6 from Jiu Fu Guo <guojiufu at gcc dot gnu.org> ---
Drafting patch to calculate three items: control, bound and cmp.
----
diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c
index 7af92d1c893..c6e4b24fd83 100644
--- a/gcc/tree-ssa-loop-niter.c
+++ b/gcc/tree-ssa-loop-niter.c
@@ -1482,7 +1482,7 @@ number_of_iterations_until_wrap (class loop *, tree type,
affine_iv *iv0,
affine_iv *iv1, class tree_niter_desc *niter)
{
tree niter_type = unsigned_type_for (type);
- tree step, num, assumptions, may_be_zero;
+ tree step, num, assumptions, may_be_zero, span;
wide_int high, low, max, min;
may_be_zero = fold_build2 (LE_EXPR, boolean_type_node, iv1->base,
iv0->base);
@@ -1513,6 +1513,8 @@ number_of_iterations_until_wrap (class loop *, tree type,
affine_iv *iv0,
low = wi::to_wide (iv0->base);
else
low = min;
+
+ niter->control = *iv1;
}
/* {base, -C} < n. */
else if (tree_int_cst_sign_bit (iv0->step) && integer_zerop (iv1->step))
@@ -1533,6 +1535,8 @@ number_of_iterations_until_wrap (class loop *, tree type,
affine_iv *iv0,
high = wi::to_wide (iv1->base);
else
high = max;
+
+ niter->control = *iv0;
}
else
return false;
@@ -1556,6 +1560,14 @@ number_of_iterations_until_wrap (class loop *, tree
type, affine_iv *iv0,
niter->assumptions, assumptions);
niter->control.no_overflow = false;
+ tree niter_m1 = fold_build2 (MINUS_EXPR, niter_type, niter->niter,
+ build_int_cst (niter_type, 1));
+ span = fold_build2 (MULT_EXPR, niter_type, niter_m1,
+ fold_convert (niter_type, niter->control.step));
+ niter->bound = fold_build2 (PLUS_EXPR, niter_type, span,
+ fold_convert (niter_type, niter->control.base));
+ niter->bound = fold_convert (type, niter->bound);
+ niter->cmp = NE_EXPR;
return true;
}
------------------------
While this code may generate complicated niter->bound if the step is not +-1.
