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| author | Mark Mitchell <mark@codesourcery.com> | 2006-04-23 18:04:33 +0000 |
|---|---|---|
| committer | Mark Mitchell <mmitchel@gcc.gnu.org> | 2006-04-23 18:04:33 +0000 |
| commit | 38a4afeecdf392267ff73a27a69f458b5d8b424c (patch) | |
| tree | 795f298e0af32f79064b451399d8021ab268f911 /gcc/cp/class.c | |
| parent | acb188c1ba3c0a94da659f679d4227f955488037 (diff) | |
| download | gcc-38a4afeecdf392267ff73a27a69f458b5d8b424c.zip gcc-38a4afeecdf392267ff73a27a69f458b5d8b424c.tar.gz gcc-38a4afeecdf392267ff73a27a69f458b5d8b424c.tar.bz2 | |
re PR c++/26534 ([4.1] bitfield wrong optimize)
2006-04-23 Mark Mitchell <mark@codesourcery.com>
PR c++/26534
* c-common.h (c_build_bitfield_integer_type): Declare.
* c-decl.c (c_build_bitfield_integer_type): Move to ...
* c-common.c (c_build_bitfield_integer_type): ... here.
2006-04-23 Mark Mitchell <mark@codesourcery.com>
PR c++/26534
* cp-tree.h (is_bitfield_expr_with_lowered_type): New function.
* typeck.c (is_bitfield_expr_with_lowered_type): New function.
(decay_conversion): Convert bitfield expressions to the correct
type.
(build_modify_expr): Remove spurious conversions.
* class.c (layout_class_type): Modify the type of bitfields to
indicate a limited range.
* call.c (standard_conversion): Adjust the type of bitfield
expressions used in an rvalue context.
(build_conditional_expr): Likewise.
2006-04-23 Mark Mitchell <mark@codesourcery.com>
PR c++/26534
* g++.dg/opt/bitfield1.C: New test.
* g++.dg/compat/abi/bitfield1_main.C: Add -w.
* g++.dg/compat/abi/bitfield1_x.C: Likewise.
* g++.dg/compat/abi/bitfield1_y.C: Likewise.
* g++.dg/compat/abi/bitfield2_main.C: Likewise.
* g++.dg/compat/abi/bitfield2_x.C: Likewise.
* g++.dg/compat/abi/bitfield2_y.C: Likewise.
* g++.dg/abi/bitfield1.C: Add dg-warning markers.
* g++.dg/abi/bitfield2.C: Likewise.
* g++.dg/init/bitfield1.C: Likewise.
From-SVN: r113199
Diffstat (limited to 'gcc/cp/class.c')
| -rw-r--r-- | gcc/cp/class.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/gcc/cp/class.c b/gcc/cp/class.c index cc26cb8..1cf87dc 100644 --- a/gcc/cp/class.c +++ b/gcc/cp/class.c @@ -4727,6 +4727,29 @@ layout_class_type (tree t, tree *virtuals_p) "classes to be placed at different locations in a " "future version of GCC", field); + /* The middle end uses the type of expressions to determine the + possible range of expression values. In order to optimize + "x.i > 7" to "false" for a 2-bit bitfield "i", the middle end + must be made aware of the width of "i", via its type. + + Because C++ does not have integer types of arbitrary width, + we must (for the purposes of the front end) convert from the + type assigned here to the declared type of the bitfield + whenever a bitfield expression is used as an rvalue. + Similarly, when assigning a value to a bitfield, the value + must be converted to the type given the bitfield here. */ + if (DECL_C_BIT_FIELD (field)) + { + tree ftype; + unsigned HOST_WIDE_INT width; + ftype = TREE_TYPE (field); + width = tree_low_cst (DECL_SIZE (field), /*unsignedp=*/1); + if (width != TYPE_PRECISION (ftype)) + TREE_TYPE (field) + = c_build_bitfield_integer_type (width, + TYPE_UNSIGNED (ftype)); + } + /* If we needed additional padding after this field, add it now. */ if (padding) |