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: Jim, hiraditya, michaelplatings, chapuni, jholewinski, arsenm, dschuff, jyknight, dylanmckay, sdardis, nemanjai, jvesely, nhaehnle, 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

llvm-svn: 362990

5 files changed, 5 insertions, 5 deletions

diff --git a/llvm/lib/Target/XCore/Disassembler/XCoreDisassembler.cpp b/llvm/lib/Target/XCore/Disassembler/XCoreDisassembler.cpp
index ff3d41fd527..230726a0283 100644
--- a/llvm/lib/Target/XCore/Disassembler/XCoreDisassembler.cpp
+++ b/llvm/lib/Target/XCore/Disassembler/XCoreDisassembler.cpp
@@ -774,7 +774,7 @@ static MCDisassembler *createXCoreDisassembler(const Target &T,
   return new XCoreDisassembler(STI, Ctx);
 }
 
-extern "C" void LLVMInitializeXCoreDisassembler() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeXCoreDisassembler() {
   // Register the disassembler.
   TargetRegistry::RegisterMCDisassembler(getTheXCoreTarget(),
                                          createXCoreDisassembler);
diff --git a/llvm/lib/Target/XCore/MCTargetDesc/XCoreMCTargetDesc.cpp b/llvm/lib/Target/XCore/MCTargetDesc/XCoreMCTargetDesc.cpp
index 877f38e22f9..715ea9d5e54 100644
--- a/llvm/lib/Target/XCore/MCTargetDesc/XCoreMCTargetDesc.cpp
+++ b/llvm/lib/Target/XCore/MCTargetDesc/XCoreMCTargetDesc.cpp
@@ -121,7 +121,7 @@ static MCTargetStreamer *createTargetAsmStreamer(MCStreamer &S,
 }
 
 // Force static initialization.
-extern "C" void LLVMInitializeXCoreTargetMC() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeXCoreTargetMC() {
   // Register the MC asm info.
   RegisterMCAsmInfoFn X(getTheXCoreTarget(), createXCoreMCAsmInfo);
 
diff --git a/llvm/lib/Target/XCore/TargetInfo/XCoreTargetInfo.cpp b/llvm/lib/Target/XCore/TargetInfo/XCoreTargetInfo.cpp
index 5604f29db3e..d5f66c2bd82 100644
--- a/llvm/lib/Target/XCore/TargetInfo/XCoreTargetInfo.cpp
+++ b/llvm/lib/Target/XCore/TargetInfo/XCoreTargetInfo.cpp
@@ -15,7 +15,7 @@ Target &llvm::getTheXCoreTarget() {
   return TheXCoreTarget;
 }
 
-extern "C" void LLVMInitializeXCoreTargetInfo() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeXCoreTargetInfo() {
   RegisterTarget<Triple::xcore> X(getTheXCoreTarget(), "xcore", "XCore",
                                   "XCore");
 }
diff --git a/llvm/lib/Target/XCore/XCoreAsmPrinter.cpp b/llvm/lib/Target/XCore/XCoreAsmPrinter.cpp
index 9f615b9e774..a0823cf81dc 100644
--- a/llvm/lib/Target/XCore/XCoreAsmPrinter.cpp
+++ b/llvm/lib/Target/XCore/XCoreAsmPrinter.cpp
@@ -292,6 +292,6 @@ void XCoreAsmPrinter::EmitInstruction(const MachineInstr *MI) {
 }
 
 // Force static initialization.
-extern "C" void LLVMInitializeXCoreAsmPrinter() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeXCoreAsmPrinter() {
   RegisterAsmPrinter<XCoreAsmPrinter> X(getTheXCoreTarget());
 }
diff --git a/llvm/lib/Target/XCore/XCoreTargetMachine.cpp b/llvm/lib/Target/XCore/XCoreTargetMachine.cpp
index 2a8cd6b657b..75d6f239248 100644
--- a/llvm/lib/Target/XCore/XCoreTargetMachine.cpp
+++ b/llvm/lib/Target/XCore/XCoreTargetMachine.cpp
@@ -105,7 +105,7 @@ void XCorePassConfig::addPreEmitPass() {
 }
 
 // Force static initialization.
-extern "C" void LLVMInitializeXCoreTarget() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeXCoreTarget() {
   RegisterTargetMachine<XCoreTargetMachine> X(getTheXCoreTarget());
 }