From: Tom de Vries Date: Thu, 16 Jun 2011 17:57:08 +0000 (+0000) Subject: re PR middle-end/45098 (Missed induction variable optimization) X-Git-Tag: releases/gcc-4.7.0~5952 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=0703f020cd4b22e0bb64612c608bfcc12a2222fd;p=thirdparty%2Fgcc.git re PR middle-end/45098 (Missed induction variable optimization) 2011-06-16 Tom de Vries PR target/45098 * tree-ssa-loop-niter.c (infer_loop_bounds_from_pointer_arith): Disallow NULL pointer for pointer arithmetic. From-SVN: r175105 --- diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 29d0f27ccabc..4ea21cf83392 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2011-06-16 Tom de Vries + + PR target/45098 + * tree-ssa-loop-niter.c (infer_loop_bounds_from_pointer_arith): Disallow + NULL pointer for pointer arithmetic. + 2011-06-16 Ramana Radhakrishnan PR target/49398 diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c index fa3ccc63f592..cf2f4556395b 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); }