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| author | Eric Botcazou <ebotcazou@libertysurf.fr> | 2003-07-02 09:41:07 +0200 |
|---|---|---|
| committer | Eric Botcazou <ebotcazou@gcc.gnu.org> | 2003-07-02 07:41:07 +0000 |
| commit | 1a8c4ca62da430aa2d8920b70f1614ab0755059b (patch) | |
| tree | 2f0ff7e67c577a96205f1a538d682dfa6c362eb3 /gcc/fold-const.c | |
| parent | 23cdfcf71f295697ac4322f0a0e8128e22e834b4 (diff) | |
| download | gcc-1a8c4ca62da430aa2d8920b70f1614ab0755059b.zip gcc-1a8c4ca62da430aa2d8920b70f1614ab0755059b.tar.gz gcc-1a8c4ca62da430aa2d8920b70f1614ab0755059b.tar.bz2 | |
re PR rtl-optimization/11210 (optimizer drops conditional with typecast from signed to unsigned char)
PR optimization/11210
* expr.c (handled_component_p) [NOP_EXPR]: Add ??? note
about the behaviour with regard to bitfields.
* fold-const (decode_field_reference): Record outermost type in
case the expression is a NOP. Strip all NOPs. Set the signedness
to that of the outermost type (if any) when the bitsize is equal
to the size of the type.
From-SVN: r68823
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 25069c5..3cc01ea 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -2625,6 +2625,7 @@ decode_field_reference (tree exp, HOST_WIDE_INT *pbitsize, HOST_WIDE_INT *pbitpo enum machine_mode *pmode, int *punsignedp, int *pvolatilep, tree *pmask, tree *pand_mask) { + tree outer_type = 0; tree and_mask = 0; tree mask, inner, offset; tree unsigned_type; @@ -2636,6 +2637,13 @@ decode_field_reference (tree exp, HOST_WIDE_INT *pbitsize, HOST_WIDE_INT *pbitpo if (! INTEGRAL_TYPE_P (TREE_TYPE (exp))) return 0; + /* We are interested in the bare arrangement of bits, so strip everything + that doesn't affect the machine mode. However, record the type of the + outermost expression if it may matter below. */ + if (TREE_CODE (exp) == NOP_EXPR + || TREE_CODE (exp) == CONVERT_EXPR + || TREE_CODE (exp) == NON_LVALUE_EXPR) + outer_type = TREE_TYPE (exp); STRIP_NOPS (exp); if (TREE_CODE (exp) == BIT_AND_EXPR) @@ -2654,6 +2662,12 @@ decode_field_reference (tree exp, HOST_WIDE_INT *pbitsize, HOST_WIDE_INT *pbitpo || TREE_CODE (inner) == PLACEHOLDER_EXPR) return 0; + /* If the number of bits in the reference is the same as the bitsize of + the outer type, then the outer type gives the signedness. Otherwise + (in case of a small bitfield) the signedness is unchanged. */ + if (outer_type && *pbitsize == tree_low_cst (TYPE_SIZE (outer_type), 1)) + *punsignedp = TREE_UNSIGNED (outer_type); + /* Compute the mask to access the bitfield. */ unsigned_type = (*lang_hooks.types.type_for_size) (*pbitsize, 1); precision = TYPE_PRECISION (unsigned_type); |