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Diffstat (limited to 'gcc/tree-ssa-loop-niter.c')
| -rw-r--r-- | gcc/tree-ssa-loop-niter.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c index fa3ccc6..cf2f455 100644 --- a/gcc/tree-ssa-loop-niter.c +++ b/gcc/tree-ssa-loop-niter.c @@ -2875,6 +2875,16 @@ infer_loop_bounds_from_pointer_arith (struct loop *loop, gimple stmt) low = lower_bound_in_type (type, type); high = upper_bound_in_type (type, type); + /* In C, pointer arithmetic p + 1 cannot use a NULL pointer, and p - 1 cannot + produce a NULL pointer. The contrary would mean NULL points to an object, + while NULL is supposed to compare unequal with the address of all objects. + Furthermore, p + 1 cannot produce a NULL pointer and p - 1 cannot use a + NULL pointer since that would mean wrapping, which we assume here not to + happen. So, we can exclude NULL from the valid range of pointer + arithmetic. */ + if (flag_delete_null_pointer_checks && int_cst_value (low) == 0) + low = build_int_cstu (TREE_TYPE (low), TYPE_ALIGN_UNIT (TREE_TYPE (type))); + record_nonwrapping_iv (loop, base, step, stmt, low, high, false, true); } |