1760effa33
This commit implements gcc_struct attribute with the behavior similar to
one in GCC. Current behavior is as follows:
When ItaniumRecordLayoutBuilder is used, [[gcc_struct]] will locally
cancel the effect of -mms-bitfields on a record. If -mms-bitfields is
not supplied and is not a default behavior on a target, [[gcc_struct]]
will be a no-op. This should provide enough compatibility with GCC.
If C++ ABI is "Microsoft", [[gcc_struct]] will currently always produce
a diagnostic, since support for it is not yet implemented in
MicrosoftRecordLayoutBuilder. Note, however, that all the infrastructure
is ready for the future implementation.
In particular, check for default value of -mms-bitfields is moved from a
driver to ASTContext, since it now non-trivially depends on other
supplied flags. This also, unfortunately, makes it impossible to use
usual argument parsing for `-m{no-,}ms-bitfields`.
The patch doesn't introduce any backwards-incompatible changes, except
for situations when cc1 is called directly with `-mms-bitfields` option.
Work towards #24757
---------
Co-authored-by: Martin Storsjö <martin@martin.st>
37 lines
1008 B
C++
37 lines
1008 B
C++
// RUN: %clang_cc1 -emit-llvm-only -triple %itanium_abi_triple -fms-layout-compatibility=itanium -fdump-record-layouts %s 2>/dev/null \
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// RUN: | FileCheck %s
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// On z/OS, a bit-field has single byte alignment. Add aligned(4) on z/OS so the union has
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// the same size & alignment as expected.
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#ifdef __MVS__
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#define ALIGN4 __attribute__((aligned(4)))
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#else
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#define ALIGN4
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#endif
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union A {
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int f1 : 3 ALIGN4;
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A();
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};
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A::A() {}
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union B {
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char f1 : 35 ALIGN4;
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B();
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};
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B::B() {}
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// CHECK:*** Dumping AST Record Layout
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// CHECK-NEXT: 0 | union A
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// CHECK-NEXT: 0:0-2 | int f1
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// CHECK-NEXT: | [sizeof=4, dsize=1, align=4{{(, preferredalign=4,)?}}
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// CHECK-NEXT: | nvsize=1, nvalign=4{{(, preferrednvalign=4)?}}]
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// CHECK:*** Dumping AST Record Layout
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// CHECK-NEXT: 0 | union B
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// CHECK-NEXT: 0:0-34 | char f1
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// CHECK-NEXT: | [sizeof=8, dsize=5, align=4{{(, preferredalign=4,)?}}
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// CHECK-NEXT: | nvsize=5, nvalign=4{{(, preferrednvalign=4)?}}]
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