From f9bb13f37b87855ae980d9e774bd54f11b8d3a3f Mon Sep 17 00:00:00 2001 From: Bernd Edlinger Date: Wed, 25 Jun 2014 17:24:34 +0000 Subject: tree-ssa-forwprop.c (associate_plusminus): For widening conversions check for undefined overflow in (T)(P + A) - (T)P -> (T)A. 2014-06-25 Bernd Edlinger * tree-ssa-forwprop.c (associate_plusminus): For widening conversions check for undefined overflow in (T)(P + A) - (T)P -> (T)A. Issue a strict overflow warning if appropriate. testsuite: 2014-06-25 Bernd Edlinger * gcc.c-torture/execute/20140622-1.c: New test. From-SVN: r211988 --- gcc/tree-ssa-forwprop.c | 35 ++++++++++++++++++++++++++++------- 1 file changed, 28 insertions(+), 7 deletions(-) (limited to 'gcc/tree-ssa-forwprop.c') diff --git a/gcc/tree-ssa-forwprop.c b/gcc/tree-ssa-forwprop.c index 33fede2..0e5e619 100644 --- a/gcc/tree-ssa-forwprop.c +++ b/gcc/tree-ssa-forwprop.c @@ -47,6 +47,7 @@ along with GCC; see the file COPYING3. If not see #include "tree-pass.h" #include "langhooks.h" #include "flags.h" +#include "diagnostic.h" #include "expr.h" #include "cfgloop.h" #include "optabs.h" @@ -2666,15 +2667,35 @@ associate_plusminus (gimple_stmt_iterator *gsi) { /* And finally (T)(P + A) - (T)P. */ tree a = gimple_assign_rhs2 (def_stmt2); - /* For pointer types, if the conversion of A to the final - type requires a sign- or zero-extension, then we have - to punt - it is not defined which one is correct. */ - if (!POINTER_TYPE_P (TREE_TYPE (rhs1)) - || TYPE_PRECISION (TREE_TYPE (rhs1)) - <= TYPE_PRECISION (TREE_TYPE (a)) - || (TREE_CODE (a) == INTEGER_CST + if (TYPE_PRECISION (TREE_TYPE (rhs1)) + <= TYPE_PRECISION (TREE_TYPE (a)) + /* For integer types, if A has a smaller type + than T the result depends on the possible + overflow in P + A. + E.g. T=size_t, A=(unsigned)429497295, P>0. + However, if an overflow in P + A would cause + undefined behavior, we can assume that there + is no overflow. */ + || (INTEGRAL_TYPE_P (TREE_TYPE (p)) + && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (p))) + /* For pointer types, if the conversion of A to the + final type requires a sign- or zero-extension, + then we have to punt - it is not defined which + one is correct. */ + || (POINTER_TYPE_P (TREE_TYPE (p)) + && TREE_CODE (a) == INTEGER_CST && tree_int_cst_sign_bit (a) == 0)) { + if (issue_strict_overflow_warning + (WARN_STRICT_OVERFLOW_MISC) + && TYPE_PRECISION (TREE_TYPE (rhs1)) + > TYPE_PRECISION (TREE_TYPE (a)) + && INTEGRAL_TYPE_P (TREE_TYPE (p))) + warning_at (gimple_location (stmt), + OPT_Wstrict_overflow, + "assuming signed overflow does not " + "occur when assuming that " + "(T)(P + A) - (T)P is always (T)A"); if (useless_type_conversion_p (TREE_TYPE (rhs1), TREE_TYPE (a))) code = TREE_CODE (a); -- cgit v1.1