diff options
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 378578d..7d8fff9 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -6966,6 +6966,18 @@ fold (tree expr) || (INTEGRAL_TYPE_P (type) && flag_wrapv && !flag_trapv))) return fold (build2 (PLUS_EXPR, type, arg0, negate_expr (arg1))); + /* Try folding difference of addresses. */ + { + HOST_WIDE_INT diff; + + if (TREE_CODE (arg0) == ADDR_EXPR + && TREE_CODE (arg1) == ADDR_EXPR + && ptr_difference_const (TREE_OPERAND (arg0, 0), + TREE_OPERAND (arg1, 0), + &diff)) + return build_int_cst_type (type, diff); + } + if (TREE_CODE (arg0) == MULT_EXPR && TREE_CODE (arg1) == MULT_EXPR && (INTEGRAL_TYPE_P (type) || flag_unsafe_math_optimizations)) @@ -10668,3 +10680,51 @@ round_down (tree value, int divisor) return value; } + +/* Returns true if addresses of E1 and E2 differ by a constant, false + otherwise. If they do, &E1 - &E2 is stored in *DIFF. */ + +bool +ptr_difference_const (tree e1, tree e2, HOST_WIDE_INT *diff) +{ + tree core1, core2; + HOST_WIDE_INT bitsize1, bitsize2; + HOST_WIDE_INT bitpos1, bitpos2; + tree toffset1, toffset2, tdiff, type; + enum machine_mode mode1, mode2; + int unsignedp1, unsignedp2, volatilep1, volatilep2; + + core1 = get_inner_reference (e1, &bitsize1, &bitpos1, &toffset1, &mode1, + &unsignedp1, &volatilep1); + core2 = get_inner_reference (e2, &bitsize2, &bitpos2, &toffset2, &mode2, + &unsignedp2, &volatilep2); + + if (bitpos1 % BITS_PER_UNIT != 0 + || bitpos2 % BITS_PER_UNIT != 0 + || !operand_equal_p (core1, core2, 0)) + return false; + + if (toffset1 && toffset2) + { + type = TREE_TYPE (toffset1); + if (type != TREE_TYPE (toffset2)) + toffset2 = fold_convert (type, toffset2); + + tdiff = fold (build2 (MINUS_EXPR, type, toffset1, toffset2)); + if (!host_integerp (tdiff, 0)) + return false; + + *diff = tree_low_cst (tdiff, 0); + } + else if (toffset1 || toffset2) + { + /* If only one of the offsets is non-constant, the difference cannot + be a constant. */ + return false; + } + else + *diff = 0; + + *diff += (bitpos1 - bitpos2) / BITS_PER_UNIT; + return true; +} |