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Specialize FORCE_DEFINING_FILE_TO_BE_LINKED using a GCC trick
to avoid using constructor calls for static objects. This reduces the number of objects requiring static constructors in a typical LLVM build by around 20%. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48665 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -26,16 +26,29 @@
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///
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/// And, foo.cp would use:<br/>
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/// <tt>DEFINING_FILE_FOR(foo)</tt><br/>
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#ifdef __GNUC__
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// If the `used' attribute is available, use it to create a variable
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// with an initializer that will force the linking of the defining file.
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#define FORCE_DEFINING_FILE_TO_BE_LINKED(name) \
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namespace llvm { \
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extern char name ## LinkVar; \
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static IncludeFile name ## LinkObj ( &name ## LinkVar ); \
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extern const char name ## LinkVar; \
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__attribute__((used)) static const char *const name ## LinkObj = \
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&name ## LinkVar; \
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}
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#else
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// Otherwise use a constructor call.
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#define FORCE_DEFINING_FILE_TO_BE_LINKED(name) \
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namespace llvm { \
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extern const char name ## LinkVar; \
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static const IncludeFile name ## LinkObj ( &name ## LinkVar ); \
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}
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#endif
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/// This macro is the counterpart to FORCE_DEFINING_FILE_TO_BE_LINKED. It should
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/// be used in a .cpp file to define the name referenced in a header file that
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/// will cause linkage of the .cpp file. It should only be used at extern level.
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#define DEFINING_FILE_FOR(name) namespace llvm { char name ## LinkVar; }
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#define DEFINING_FILE_FOR(name) \
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namespace llvm { const char name ## LinkVar = 0; }
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namespace llvm {
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@ -57,7 +70,7 @@ namespace llvm {
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/// <tt>static IncludeFile LinkMyModule(&LinkMyCodeStub);</tt><br/>
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/// @brief Class to ensure linking of corresponding object file.
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struct IncludeFile {
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IncludeFile(void *);
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explicit IncludeFile(const void *);
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};
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}
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@ -17,4 +17,4 @@ using namespace llvm;
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// This constructor is used to ensure linking of other modules. See the
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// llvm/System/IncludeFile.h header for details.
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IncludeFile::IncludeFile(void*) {}
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IncludeFile::IncludeFile(const void*) {}
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