diff options
| author | James A. Morrison <phython@gcc.gnu.org> | 2005-06-12 08:03:23 +0000 |
|---|---|---|
| committer | James A. Morrison <phython@gcc.gnu.org> | 2005-06-12 08:03:23 +0000 |
| commit | 13d61949ea3014f28b9285218b1e5b096e06b321 (patch) | |
| tree | 341f5a35ba0116afe7ce890b2b5c25eed5beff64 /gcc/fold-const.c | |
| parent | 9401be5d1b5e97db751cf687deff5455d41cdb0b (diff) | |
2005-06-12 James A. Morrison <phython@gcc.gnu.org>
PR tree-optimization/14796
* fold-const.c (fold_binary): Transform (A >> C) << C into
one BIT_AND_EXPR.
<shift>: Transform (A OP c1) OP c2 into A OP (c1 + c2).
git-svn-id: https://gcc.gnu.org/svn/gcc/trunk@100853 138bc75d-0d04-0410-961f-82ee72b054a4
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 96fffe995d4..1994410d4be 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -8742,6 +8742,59 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1) don't try to compute it in the compiler. */ if (TREE_CODE (arg1) == INTEGER_CST && tree_int_cst_sgn (arg1) < 0) return NULL_TREE; + + /* Turn (a OP c1) OP c2 into a OP (c1+c2). */ + if (TREE_CODE (arg0) == code && host_integerp (arg1, false) + && TREE_INT_CST_LOW (arg1) < TYPE_PRECISION (type) + && host_integerp (TREE_OPERAND (arg0, 1), false) + && TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1)) < TYPE_PRECISION (type)) + { + HOST_WIDE_INT low = (TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1)) + + TREE_INT_CST_LOW (arg1)); + + /* Deal with a OP (c1 + c2) being undefined but (a OP c1) OP c2 + being well defined. */ + if (low >= TYPE_PRECISION (type)) + { + if (code == LROTATE_EXPR || code == RROTATE_EXPR) + low = low % TYPE_PRECISION (type); + else if (TYPE_UNSIGNED (type) || code == LSHIFT_EXPR) + return build_int_cst (type, 0); + else + low = TYPE_PRECISION (type) - 1; + } + + return fold_build2 (code, type, TREE_OPERAND (arg0, 0), + build_int_cst (type, low)); + } + + /* Transform (x >> c) << c into x & (-1<<c) */ + if (code == LSHIFT_EXPR && TREE_CODE (arg0) == RSHIFT_EXPR + && host_integerp (arg1, false) + && TREE_INT_CST_LOW (arg1) < TYPE_PRECISION (type) + && host_integerp (TREE_OPERAND (arg0, 1), false) + && TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1)) < TYPE_PRECISION (type)) + { + HOST_WIDE_INT low0 = TREE_INT_CST_LOW (TREE_OPERAND (arg0, 1)); + HOST_WIDE_INT low1 = TREE_INT_CST_LOW (arg1); + unsigned HOST_WIDE_INT low; + HOST_WIDE_INT high; + tree lshift; + tree arg00; + + if (low0 == low1) + { + arg00 = fold_convert (type, TREE_OPERAND (arg0, 0)); + + lshift_double (-1, -1, low0 < low1 ? low0 : low1, + TYPE_PRECISION (type), &low, &high, 1); + lshift = build_int_cst_wide (type, low, high); + + return fold_build2 (BIT_AND_EXPR, type, arg00, lshift); + } + } + + /* Rewrite an LROTATE_EXPR by a constant into an RROTATE_EXPR by a new constant. */ if (code == LROTATE_EXPR && TREE_CODE (arg1) == INTEGER_CST) |