diff options
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 30efccd..b04022e 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -7835,6 +7835,48 @@ fold_comparison (enum tree_code code, tree type, tree op0, tree op1) } } + /* Transform comparisons of the form X +- C1 CMP Y +- C2 to + X CMP Y +- C2 +- C1 for signed X, Y. This is valid if + the resulting offset is smaller in absolute value than the + original one. */ + if (!(flag_wrapv || flag_trapv) + && !TYPE_UNSIGNED (TREE_TYPE (arg0)) + && (TREE_CODE (arg0) == PLUS_EXPR || TREE_CODE (arg0) == MINUS_EXPR) + && (TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST + && !TREE_OVERFLOW (TREE_OPERAND (arg0, 1))) + && (TREE_CODE (arg1) == PLUS_EXPR || TREE_CODE (arg1) == MINUS_EXPR) + && (TREE_CODE (TREE_OPERAND (arg1, 1)) == INTEGER_CST + && !TREE_OVERFLOW (TREE_OPERAND (arg1, 1)))) + { + tree const1 = TREE_OPERAND (arg0, 1); + tree const2 = TREE_OPERAND (arg1, 1); + tree variable1 = TREE_OPERAND (arg0, 0); + tree variable2 = TREE_OPERAND (arg1, 0); + tree cst; + + /* Put the constant on the side where it doesn't overflow and is + of lower absolute value than before. */ + cst = int_const_binop (TREE_CODE (arg0) == TREE_CODE (arg1) + ? MINUS_EXPR : PLUS_EXPR, + const2, const1, 0); + if (!TREE_OVERFLOW (cst) + && tree_int_cst_compare (const2, cst) == tree_int_cst_sgn (const2)) + return fold_build2 (code, type, + variable1, + fold_build2 (TREE_CODE (arg1), TREE_TYPE (arg1), + variable2, cst)); + + cst = int_const_binop (TREE_CODE (arg0) == TREE_CODE (arg1) + ? MINUS_EXPR : PLUS_EXPR, + const1, const2, 0); + if (!TREE_OVERFLOW (cst) + && tree_int_cst_compare (const1, cst) == tree_int_cst_sgn (const1)) + return fold_build2 (code, type, + fold_build2 (TREE_CODE (arg0), TREE_TYPE (arg0), + variable1, cst), + variable2); + } + if (FLOAT_TYPE_P (TREE_TYPE (arg0))) { tree targ0 = strip_float_extensions (arg0); |