This patch came out of a discussion held in the gcc mailing list (https://gcc.gnu.org/ml/gcc/2015-11/msg00067.html).
The patch restricts folding of conditional exprs with lhs previously set by a type conversion to occur only if the source of the type conversion's mode is word mode or smaller. Bootstrapped and reg tested on x86_64 (with --enable-languages=c,c++). If ok, could you commit please? I don't have commit access. Regards Senthil gcc/ChangeLog 2015-11-11 Senthil Kumar Selvaraj <senthil_kumar.selva...@atmel.com> * tree-vrp.c (simplify_cond_using_ranges): Fold only if innerop's mode is word_mode or smaller. diff --git gcc/tree-vrp.c gcc/tree-vrp.c index e2393e4..c139bc6 100644 --- gcc/tree-vrp.c +++ gcc/tree-vrp.c @@ -9467,6 +9467,8 @@ simplify_cond_using_ranges (gcond *stmt) innerop = gimple_assign_rhs1 (def_stmt); if (TREE_CODE (innerop) == SSA_NAME + && (GET_MODE_SIZE(TYPE_MODE(TREE_TYPE(innerop))) + <= GET_MODE_SIZE(word_mode)) && !POINTER_TYPE_P (TREE_TYPE (innerop))) { value_range *vr = get_value_range (innerop);