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| author | Richard Guenther <rguenther@suse.de> | 2005-07-26 07:34:58 +0000 |
|---|---|---|
| committer | Richard Biener <rguenth@gcc.gnu.org> | 2005-07-26 07:34:58 +0000 |
| commit | 46c0a59dfb7e787766e70fae751b66e527a8932a (patch) | |
| tree | 0c96be52bba7fbb40aef73b7e70cfd92198df875 /gcc/fold-const.c | |
| parent | 3e2844cb07459014e55308e43ec26dd75e280f30 (diff) | |
| download | gcc-46c0a59dfb7e787766e70fae751b66e527a8932a.zip gcc-46c0a59dfb7e787766e70fae751b66e527a8932a.tar.gz gcc-46c0a59dfb7e787766e70fae751b66e527a8932a.tar.bz2 | |
re PR tree-optimization/22486 (Upcasts are not folded away)
2005-07-26 Richard Guenther <rguenther@suse.de>
PR tree-optimization/22486
* fold-const.c (fold_unary): Fold away useless component
references of the form (T *)&T.x, if the address
doesn't change.
* gcc.dg/tree-ssa/upcast-1.c: New testcase.
From-SVN: r102381
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 9a9ea22..bdda600 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -6711,6 +6711,29 @@ fold_unary (enum tree_code code, tree type, tree op0) return fold_build1 (code, type, TREE_OPERAND (op0, 0)); } + /* Handle (T *)&A.B.C for A being of type T and B and C + living at offset zero. This occours frequently in + C++ upcasting and then accessing the base. */ + if (TREE_CODE (op0) == ADDR_EXPR + && POINTER_TYPE_P (type) + && handled_component_p (TREE_OPERAND (op0, 0))) + { + HOST_WIDE_INT bitsize, bitpos; + tree offset; + enum machine_mode mode; + int unsignedp, volatilep; + tree base = TREE_OPERAND (op0, 0); + base = get_inner_reference (base, &bitsize, &bitpos, &offset, + &mode, &unsignedp, &volatilep, false); + /* If the reference was to a (constant) zero offset, we can use + the address of the base if it has the same base type + as the result type. */ + if (! offset && bitpos == 0 + && TYPE_MAIN_VARIANT (TREE_TYPE (type)) + == TYPE_MAIN_VARIANT (TREE_TYPE (base))) + return fold_convert (type, build_fold_addr_expr (base)); + } + if (TREE_CODE (op0) == MODIFY_EXPR && TREE_CONSTANT (TREE_OPERAND (op0, 1)) /* Detect assigning a bitfield. */ |