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| author | sayle <sayle@138bc75d-0d04-0410-961f-82ee72b054a4> | 2006-02-18 05:22:46 +0000 |
|---|---|---|
| committer | sayle <sayle@138bc75d-0d04-0410-961f-82ee72b054a4> | 2006-02-18 05:22:46 +0000 |
| commit | 819aeb26f6dcc0f1759eed90116a5f9e9e0e480d (patch) | |
| tree | 4d37d7702bbfbd33a364527a6c3b6ba57cad4e0a /gcc/fold-const.c | |
| parent | 003f258f2ea9f8e5ee0e750e898b317b7cad9fac (diff) | |
| download | gcc-819aeb26f6dcc0f1759eed90116a5f9e9e0e480d.tar.gz | |
PR middle-end/25600
* fold-const.c (fold_binary): Fold (X >> C) != 0 into X < 0 when
C is one less than the width of X (and related transformations).
* simplify_rtx.c (simplify_unary_operation_1): Transform
(neg (lt x 0)) into either (ashiftrt X C) or (lshiftrt X C)
depending on STORE_FLAG_VALUE, were C is one less then the
width of X.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@111226 138bc75d-0d04-0410-961f-82ee72b054a4
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 7413883a904..c77e7ba82eb 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -10042,6 +10042,30 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1) return t1; } + /* Fold (X >> C) != 0 into X < 0 if C is one less than the width + of X. Similarly fold (X >> C) == 0 into X >= 0. */ + if ((code == EQ_EXPR || code == NE_EXPR) + && integer_zerop (arg1) + && TREE_CODE (arg0) == RSHIFT_EXPR + && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST) + { + tree arg00 = TREE_OPERAND (arg0, 0); + tree arg01 = TREE_OPERAND (arg0, 1); + tree itype = TREE_TYPE (arg00); + if (TREE_INT_CST_HIGH (arg01) == 0 + && TREE_INT_CST_LOW (arg01) + == (unsigned HOST_WIDE_INT) (TYPE_PRECISION (itype) - 1)) + { + if (TYPE_UNSIGNED (itype)) + { + itype = lang_hooks.types.signed_type (itype); + arg00 = fold_convert (itype, arg00); + } + return fold_build2 (code == EQ_EXPR ? GE_EXPR : LT_EXPR, + type, arg00, build_int_cst (itype, 0)); + } + } + if ((code == EQ_EXPR || code == NE_EXPR) && integer_zerop (arg1) && tree_expr_nonzero_p (arg0)) |