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

6 files changed, 6 insertions, 6 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp b/llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp
index 42a667b67bf..9e07b4d252b 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp
@@ -90,7 +90,7 @@ createAMDGPUAsmPrinterPass(TargetMachine &tm,
   return new AMDGPUAsmPrinter(tm, std::move(Streamer));
 }
 
-extern "C" void LLVMInitializeAMDGPUAsmPrinter() {
+extern "C" void LLVM_EXTERNAL_VISIBILITY LLVMInitializeAMDGPUAsmPrinter() {
   TargetRegistry::RegisterAsmPrinter(getTheAMDGPUTarget(),
                                      llvm::createR600AsmPrinterPass);
   TargetRegistry::RegisterAsmPrinter(getTheGCNTarget(),
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
index 57853963b01..c8dc6f6e3bf 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
@@ -183,7 +183,7 @@ static cl::opt<bool> EnableScalarIRPasses(
   cl::init(true),
   cl::Hidden);
 
-extern "C" void LLVMInitializeAMDGPUTarget() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAMDGPUTarget() {
   // Register the target
   RegisterTargetMachine<R600TargetMachine> X(getTheAMDGPUTarget());
   RegisterTargetMachine<GCNTargetMachine> Y(getTheGCNTarget());
diff --git a/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp b/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
index d5834826fcd..f3aa1a58236 100644
--- a/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
+++ b/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
@@ -6980,7 +6980,7 @@ AMDGPUOperand::Ptr AMDGPUAsmParser::defaultABID() const {
 }
 
 /// Force static initialization.
-extern "C" void LLVMInitializeAMDGPUAsmParser() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAMDGPUAsmParser() {
   RegisterMCAsmParser<AMDGPUAsmParser> A(getTheAMDGPUTarget());
   RegisterMCAsmParser<AMDGPUAsmParser> B(getTheGCNTarget());
 }
diff --git a/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp b/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
index 968d653bd74..419513bdc24 100644
--- a/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
+++ b/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
@@ -1252,7 +1252,7 @@ static MCDisassembler *createAMDGPUDisassembler(const Target &T,
   return new AMDGPUDisassembler(STI, Ctx, T.createMCInstrInfo());
 }
 
-extern "C" void LLVMInitializeAMDGPUDisassembler() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAMDGPUDisassembler() {
   TargetRegistry::RegisterMCDisassembler(getTheGCNTarget(),
                                          createAMDGPUDisassembler);
   TargetRegistry::RegisterMCSymbolizer(getTheGCNTarget(),
diff --git a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCTargetDesc.cpp b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCTargetDesc.cpp
index 88df64d18cc..9507836c64c 100644
--- a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCTargetDesc.cpp
+++ b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCTargetDesc.cpp
@@ -134,7 +134,7 @@ static MCInstrAnalysis *createAMDGPUMCInstrAnalysis(const MCInstrInfo *Info) {
   return new AMDGPUMCInstrAnalysis(Info);
 }
 
-extern "C" void LLVMInitializeAMDGPUTargetMC() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAMDGPUTargetMC() {
 
   TargetRegistry::RegisterMCInstrInfo(getTheGCNTarget(), createAMDGPUMCInstrInfo);
   TargetRegistry::RegisterMCInstrInfo(getTheAMDGPUTarget(), createR600MCInstrInfo);
diff --git a/llvm/lib/Target/AMDGPU/TargetInfo/AMDGPUTargetInfo.cpp b/llvm/lib/Target/AMDGPU/TargetInfo/AMDGPUTargetInfo.cpp
index 30cf12337c6..9ec437760c0 100644
--- a/llvm/lib/Target/AMDGPU/TargetInfo/AMDGPUTargetInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/TargetInfo/AMDGPUTargetInfo.cpp
@@ -28,7 +28,7 @@ Target &llvm::getTheGCNTarget() {
 }
 
 /// Extern function to initialize the targets for the AMDGPU backend
-extern "C" void LLVMInitializeAMDGPUTargetInfo() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAMDGPUTargetInfo() {
   RegisterTarget<Triple::r600, false> R600(getTheAMDGPUTarget(), "r600",
                                            "AMD GPUs HD2XXX-HD6XXX", "AMDGPU");
   RegisterTarget<Triple::amdgcn, false> GCN(getTheGCNTarget(), "amdgcn",