diff options
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 53 |
1 files changed, 37 insertions, 16 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 25fa071..ed6ae0f 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -865,14 +865,44 @@ negate_mathfn_p (enum built_in_function code) return false; } +/* Check whether we may negate an integer constant T without causing + overflow. */ + +bool +may_negate_without_overflow_p (tree t) +{ + unsigned HOST_WIDE_INT val; + unsigned int prec; + tree type; + + if (TREE_CODE (t) != INTEGER_CST) + abort (); + + type = TREE_TYPE (t); + if (TYPE_UNSIGNED (type)) + return false; + + prec = TYPE_PRECISION (type); + if (prec > HOST_BITS_PER_WIDE_INT) + { + if (TREE_INT_CST_LOW (t) != 0) + return true; + prec -= HOST_BITS_PER_WIDE_INT; + val = TREE_INT_CST_HIGH (t); + } + else + val = TREE_INT_CST_LOW (t); + if (prec < HOST_BITS_PER_WIDE_INT) + val &= ((unsigned HOST_WIDE_INT) 1 << prec) - 1; + return val != ((unsigned HOST_WIDE_INT) 1 << (prec - 1)); +} + /* Determine whether an expression T can be cheaply negated using the function negate_expr. */ static bool negate_expr_p (tree t) { - unsigned HOST_WIDE_INT val; - unsigned int prec; tree type; if (t == 0) @@ -888,19 +918,7 @@ negate_expr_p (tree t) return true; /* Check that -CST will not overflow type. */ - prec = TYPE_PRECISION (type); - if (prec > HOST_BITS_PER_WIDE_INT) - { - if (TREE_INT_CST_LOW (t) != 0) - return true; - prec -= HOST_BITS_PER_WIDE_INT; - val = TREE_INT_CST_HIGH (t); - } - else - val = TREE_INT_CST_LOW (t); - if (prec < HOST_BITS_PER_WIDE_INT) - val &= ((unsigned HOST_WIDE_INT) 1 << prec) - 1; - return val != ((unsigned HOST_WIDE_INT) 1 << (prec - 1)); + return may_negate_without_overflow_p (t); case REAL_CST: case NEGATE_EXPR: @@ -9615,7 +9633,10 @@ tree_expr_nonzero_p (tree t) return tree_expr_nonzero_p (TREE_OPERAND (t, 0)); case INTEGER_CST: - return !integer_zerop (t); + /* We used to test for !integer_zerop here. This does not work correctly + if TREE_CONSTANT_OVERFLOW (t). */ + return (TREE_INT_CST_LOW (t) != 0 + || TREE_INT_CST_HIGH (t) != 0); case PLUS_EXPR: if (!TYPE_UNSIGNED (type) && !flag_wrapv) |