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

6 files changed, 6 insertions, 6 deletions

diff --git a/llvm/lib/Target/AVR/AVRAsmPrinter.cpp b/llvm/lib/Target/AVR/AVRAsmPrinter.cpp
index 7586bd7b78f..80b802e8201 100644
--- a/llvm/lib/Target/AVR/AVRAsmPrinter.cpp
+++ b/llvm/lib/Target/AVR/AVRAsmPrinter.cpp
@@ -178,7 +178,7 @@ void AVRAsmPrinter::EmitInstruction(const MachineInstr *MI) {
 
 } // end of namespace llvm
 
-extern "C" void LLVMInitializeAVRAsmPrinter() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAVRAsmPrinter() {
   llvm::RegisterAsmPrinter<llvm::AVRAsmPrinter> X(llvm::getTheAVRTarget());
 }
 
diff --git a/llvm/lib/Target/AVR/AVRTargetMachine.cpp b/llvm/lib/Target/AVR/AVRTargetMachine.cpp
index a36c8b0f964..98de6d320b0 100644
--- a/llvm/lib/Target/AVR/AVRTargetMachine.cpp
+++ b/llvm/lib/Target/AVR/AVRTargetMachine.cpp
@@ -76,7 +76,7 @@ TargetPassConfig *AVRTargetMachine::createPassConfig(PassManagerBase &PM) {
   return new AVRPassConfig(*this, PM);
 }
 
-extern "C" void LLVMInitializeAVRTarget() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAVRTarget() {
   // Register the target.
   RegisterTargetMachine<AVRTargetMachine> X(getTheAVRTarget());
 
diff --git a/llvm/lib/Target/AVR/AsmParser/AVRAsmParser.cpp b/llvm/lib/Target/AVR/AsmParser/AVRAsmParser.cpp
index aac5644711e..4db17459f53 100644
--- a/llvm/lib/Target/AVR/AsmParser/AVRAsmParser.cpp
+++ b/llvm/lib/Target/AVR/AsmParser/AVRAsmParser.cpp
@@ -682,7 +682,7 @@ bool AVRAsmParser::parseLiteralValues(unsigned SizeInBytes, SMLoc L) {
   return (parseMany(parseOne));
 }
 
-extern "C" void LLVMInitializeAVRAsmParser() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAVRAsmParser() {
   RegisterMCAsmParser<AVRAsmParser> X(getTheAVRTarget());
 }
 
diff --git a/llvm/lib/Target/AVR/Disassembler/AVRDisassembler.cpp b/llvm/lib/Target/AVR/Disassembler/AVRDisassembler.cpp
index e203a5069c8..9d88cd33600 100644
--- a/llvm/lib/Target/AVR/Disassembler/AVRDisassembler.cpp
+++ b/llvm/lib/Target/AVR/Disassembler/AVRDisassembler.cpp
@@ -52,7 +52,7 @@ static MCDisassembler *createAVRDisassembler(const Target &T,
 }
 
 
-extern "C" void LLVMInitializeAVRDisassembler() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAVRDisassembler() {
   // Register the disassembler.
   TargetRegistry::RegisterMCDisassembler(getTheAVRTarget(),
                                          createAVRDisassembler);
diff --git a/llvm/lib/Target/AVR/MCTargetDesc/AVRMCTargetDesc.cpp b/llvm/lib/Target/AVR/MCTargetDesc/AVRMCTargetDesc.cpp
index f6607b26a06..bfc274d9cdc 100644
--- a/llvm/lib/Target/AVR/MCTargetDesc/AVRMCTargetDesc.cpp
+++ b/llvm/lib/Target/AVR/MCTargetDesc/AVRMCTargetDesc.cpp
@@ -89,7 +89,7 @@ static MCTargetStreamer *createMCAsmTargetStreamer(MCStreamer &S,
   return new AVRTargetAsmStreamer(S);
 }
 
-extern "C" void LLVMInitializeAVRTargetMC() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAVRTargetMC() {
   // Register the MC asm info.
   RegisterMCAsmInfo<AVRMCAsmInfo> X(getTheAVRTarget());
 
diff --git a/llvm/lib/Target/AVR/TargetInfo/AVRTargetInfo.cpp b/llvm/lib/Target/AVR/TargetInfo/AVRTargetInfo.cpp
index c62d5cb85bc..69b509b33e8 100644
--- a/llvm/lib/Target/AVR/TargetInfo/AVRTargetInfo.cpp
+++ b/llvm/lib/Target/AVR/TargetInfo/AVRTargetInfo.cpp
@@ -15,7 +15,7 @@ Target &getTheAVRTarget() {
 }
 }
 
-extern "C" void LLVMInitializeAVRTargetInfo() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAVRTargetInfo() {
   llvm::RegisterTarget<llvm::Triple::avr> X(llvm::getTheAVRTarget(), "avr",
                                             "Atmel AVR Microcontroller", "AVR");
 }