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/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp b/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
index 44136b69efe..a8d88154cfa 100644
--- a/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
+++ b/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
@@ -764,7 +764,7 @@ public:
 } // end anonymous namespace
 
 // Force static initialization.
-extern "C" void LLVMInitializeWebAssemblyAsmParser() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeWebAssemblyAsmParser() {
   RegisterMCAsmParser<WebAssemblyAsmParser> X(getTheWebAssemblyTarget32());
   RegisterMCAsmParser<WebAssemblyAsmParser> Y(getTheWebAssemblyTarget64());
 }
diff --git a/llvm/lib/Target/WebAssembly/Disassembler/WebAssemblyDisassembler.cpp b/llvm/lib/Target/WebAssembly/Disassembler/WebAssemblyDisassembler.cpp
index f9bf3f85d30..60e55499baf 100644
--- a/llvm/lib/Target/WebAssembly/Disassembler/WebAssemblyDisassembler.cpp
+++ b/llvm/lib/Target/WebAssembly/Disassembler/WebAssemblyDisassembler.cpp
@@ -65,7 +65,7 @@ static MCDisassembler *createWebAssemblyDisassembler(const Target &T,
   return new WebAssemblyDisassembler(STI, Ctx, std::move(MCII));
 }
 
-extern "C" void LLVMInitializeWebAssemblyDisassembler() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeWebAssemblyDisassembler() {
   // Register the disassembler for each target.
   TargetRegistry::RegisterMCDisassembler(getTheWebAssemblyTarget32(),
                                          createWebAssemblyDisassembler);
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.cpp
index 21545c39164..82e8e91afdd 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.cpp
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.cpp
@@ -95,7 +95,7 @@ static MCTargetStreamer *createNullTargetStreamer(MCStreamer &S) {
 }
 
 // Force static initialization.
-extern "C" void LLVMInitializeWebAssemblyTargetMC() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeWebAssemblyTargetMC() {
   for (Target *T :
        {&getTheWebAssemblyTarget32(), &getTheWebAssemblyTarget64()}) {
     // Register the MC asm info.
diff --git a/llvm/lib/Target/WebAssembly/TargetInfo/WebAssemblyTargetInfo.cpp b/llvm/lib/Target/WebAssembly/TargetInfo/WebAssemblyTargetInfo.cpp
index e4afe2bb283..87317f8a7f1 100644
--- a/llvm/lib/Target/WebAssembly/TargetInfo/WebAssemblyTargetInfo.cpp
+++ b/llvm/lib/Target/WebAssembly/TargetInfo/WebAssemblyTargetInfo.cpp
@@ -26,7 +26,7 @@ Target &llvm::getTheWebAssemblyTarget64() {
   return TheWebAssemblyTarget64;
 }
 
-extern "C" void LLVMInitializeWebAssemblyTargetInfo() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeWebAssemblyTargetInfo() {
   RegisterTarget<Triple::wasm32> X(getTheWebAssemblyTarget32(), "wasm32",
                                    "WebAssembly 32-bit", "WebAssembly");
   RegisterTarget<Triple::wasm64> Y(getTheWebAssemblyTarget64(), "wasm64",
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
index 7f9d41da397..97f14a2d698 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
@@ -443,7 +443,7 @@ bool WebAssemblyAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
 }
 
 // Force static initialization.
-extern "C" void LLVMInitializeWebAssemblyAsmPrinter() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeWebAssemblyAsmPrinter() {
   RegisterAsmPrinter<WebAssemblyAsmPrinter> X(getTheWebAssemblyTarget32());
   RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(getTheWebAssemblyTarget64());
 }
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
index 937d272d213..9f45a0dca27 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
@@ -45,7 +45,7 @@ static cl::opt<bool> EnableEmSjLj(
     cl::desc("WebAssembly Emscripten-style setjmp/longjmp handling"),
     cl::init(false));
 
-extern "C" void LLVMInitializeWebAssemblyTarget() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeWebAssemblyTarget() {
   // Register the target.
   RegisterTargetMachine<WebAssemblyTargetMachine> X(
       getTheWebAssemblyTarget32());