Commit 0dbcb363 authored by Tom Stellard's avatar Tom Stellard
Browse files

CMake: Make most target symbols hidden by default 

Summary:
For builds with LLVM_BUILD_LLVM_DYLIB=ON and BUILD_SHARED_LIBS=OFF
this change makes all symbols in the target specific libraries hidden
by default.

A new macro called LLVM_EXTERNAL_VISIBILITY has been added to mark symbols in these
libraries public, which is mainly needed for the definitions of the
LLVMInitialize* functions.

This patch reduces the number of public symbols in libLLVM.so by about
25%.  This should improve load times for the dynamic library and also
make abi checker tools, like abidiff require less memory when analyzing
libLLVM.so

One side-effect of this change is that for builds with
LLVM_BUILD_LLVM_DYLIB=ON and LLVM_LINK_LLVM_DYLIB=ON some unittests that
access symbols that are no longer public will need to be statically linked.

Before and after public symbol counts (using gcc 8.2.1, ld.bfd 2.31.1):
nm before/libLLVM-9svn.so | grep ' [A-Zuvw] ' | wc -l
36221
nm after/libLLVM-9svn.so | grep ' [A-Zuvw] ' | wc -l
26278

Reviewers: chandlerc, beanz, mgorny, rnk, hans

Reviewed By: rnk, hans

Subscribers: merge_guards_bot, luismarques, smeenai, ldionne, lenary, s.egerton, pzheng, sameer.abuasal, MaskRay, wuzish, echristo, Jim, hiraditya, michaelplatings, chapuni, jholewinski, arsenm, dschuff, jyknight, dylanmckay, sdardis, nemanjai, jvesely, javed.absar, sbc100, jgravelle-google, aheejin, kbarton, fedor.sergeev, asb, rbar, johnrusso, simoncook, apazos, sabuasal, niosHD, jrtc27, zzheng, edward-jones, mgrang, atanasyan, rogfer01, MartinMosbeck, brucehoult, the_o, PkmX, jocewei, kristina, jsji, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D54439
parent 1b5404af

llvm/include/llvm/Support/Compiler.h

+6 −0
Original line number Diff line number Diff line
@@ -117,11 +117,17 @@ 
/// not accessible from outside it.  Can also be used to mark variables and

/// functions, making them private to any shared library they are linked into.

/// On PE/COFF targets, library visibility is the default, so this isn't needed.

///

/// LLVM_EXTERNAL_VISIBILITY - classes, functions, and variables marked with

/// this attribute will be made public and visible outside of any shared library

/// they are linked in to.

#if (__has_attribute(visibility) || LLVM_GNUC_PREREQ(4, 0, 0)) &&              \

    !defined(__MINGW32__) && !defined(__CYGWIN__) && !defined(_WIN32)

#define LLVM_LIBRARY_VISIBILITY __attribute__ ((visibility("hidden")))

#define LLVM_EXTERNAL_VISIBILITY __attribute__ ((visibility("default")))

#else

#define LLVM_LIBRARY_VISIBILITY

#define LLVM_EXTERNAL_VISIBILITY

#endif



#if defined(__GNUC__)

llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp

+1 −1
Original line number Diff line number Diff line
@@ -1298,7 +1298,7 @@ void AArch64AsmPrinter::EmitInstruction(const MachineInstr *MI) { 
}



// Force static initialization.

extern "C" void LLVMInitializeAArch64AsmPrinter() {

extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAArch64AsmPrinter() {

  RegisterAsmPrinter<AArch64AsmPrinter> X(getTheAArch64leTarget());

  RegisterAsmPrinter<AArch64AsmPrinter> Y(getTheAArch64beTarget());

  RegisterAsmPrinter<AArch64AsmPrinter> Z(getTheARM64Target());

llvm/lib/Target/AArch64/AArch64TargetMachine.cpp

+1 −1
Original line number Diff line number Diff line
@@ -154,7 +154,7 @@ static cl::opt<bool> 
                        cl::desc("Enable the AAcrh64 branch target pass"),

                        cl::init(true));



extern "C" void LLVMInitializeAArch64Target() {

extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAArch64Target() {

  // Register the target.

  RegisterTargetMachine<AArch64leTargetMachine> X(getTheAArch64leTarget());

  RegisterTargetMachine<AArch64beTargetMachine> Y(getTheAArch64beTarget());

llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp

+1 −1
Original line number Diff line number Diff line
@@ -5515,7 +5515,7 @@ AArch64AsmParser::classifySymbolRef(const MCExpr *Expr, 
}



/// Force static initialization.

extern "C" void LLVMInitializeAArch64AsmParser() {

extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAArch64AsmParser() {

  RegisterMCAsmParser<AArch64AsmParser> X(getTheAArch64leTarget());

  RegisterMCAsmParser<AArch64AsmParser> Y(getTheAArch64beTarget());

  RegisterMCAsmParser<AArch64AsmParser> Z(getTheARM64Target());

llvm/lib/Target/AArch64/Disassembler/AArch64Disassembler.cpp

+1 −1
Original line number Diff line number Diff line
@@ -277,7 +277,7 @@ createAArch64ExternalSymbolizer(const Triple &TT, LLVMOpInfoCallback GetOpInfo, 
                                       SymbolLookUp, DisInfo);

}



extern "C" void LLVMInitializeAArch64Disassembler() {

extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAArch64Disassembler() {

  TargetRegistry::RegisterMCDisassembler(getTheAArch64leTarget(),

                                         createAArch64Disassembler);

  TargetRegistry::RegisterMCDisassembler(getTheAArch64beTarget(),