diff options
Diffstat (limited to 'gcc/tree-ssa-loop-niter.c')
| -rw-r--r-- | gcc/tree-ssa-loop-niter.c | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c index 7510940..06954e4 100644 --- a/gcc/tree-ssa-loop-niter.c +++ b/gcc/tree-ssa-loop-niter.c @@ -1478,7 +1478,7 @@ assert_loop_rolls_lt (tree type, affine_iv *iv0, affine_iv *iv1, The number of iterations is stored to NITER. */ static bool -number_of_iterations_until_wrap (class loop *, tree type, affine_iv *iv0, +number_of_iterations_until_wrap (class loop *loop, tree type, affine_iv *iv0, affine_iv *iv1, class tree_niter_desc *niter) { tree niter_type = unsigned_type_for (type); @@ -1506,6 +1506,23 @@ number_of_iterations_until_wrap (class loop *, tree type, affine_iv *iv0, num = fold_build2 (MINUS_EXPR, niter_type, wide_int_to_tree (type, max), iv1->base); + + /* When base has the form iv + 1, if we know iv >= n, then iv + 1 < n + only when iv + 1 overflows, i.e. when iv == TYPE_VALUE_MAX. */ + if (sgn == UNSIGNED + && integer_onep (step) + && TREE_CODE (iv1->base) == PLUS_EXPR + && integer_onep (TREE_OPERAND (iv1->base, 1))) + { + tree cond = fold_build2 (GE_EXPR, boolean_type_node, + TREE_OPERAND (iv1->base, 0), iv0->base); + cond = simplify_using_initial_conditions (loop, cond); + if (integer_onep (cond)) + may_be_zero = fold_build2 (EQ_EXPR, boolean_type_node, + TREE_OPERAND (iv1->base, 0), + TYPE_MAX_VALUE (type)); + } + high = max; if (TREE_CODE (iv1->base) == INTEGER_CST) low = wi::to_wide (iv1->base) - 1; |