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/PowerPC/AsmParser/PPCAsmParser.cpp b/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
index eedbdd3aaf0..7e7902c27a8 100644
--- a/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
+++ b/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
@@ -1786,7 +1786,7 @@ bool PPCAsmParser::ParseDirectiveLocalEntry(SMLoc L) {
 
 
 /// Force static initialization.
-extern "C" void LLVMInitializePowerPCAsmParser() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializePowerPCAsmParser() {
   RegisterMCAsmParser<PPCAsmParser> A(getThePPC32Target());
   RegisterMCAsmParser<PPCAsmParser> B(getThePPC64Target());
   RegisterMCAsmParser<PPCAsmParser> C(getThePPC64LETarget());
diff --git a/llvm/lib/Target/PowerPC/Disassembler/PPCDisassembler.cpp b/llvm/lib/Target/PowerPC/Disassembler/PPCDisassembler.cpp
index 935fa066244..e3c0f958c7e 100644
--- a/llvm/lib/Target/PowerPC/Disassembler/PPCDisassembler.cpp
+++ b/llvm/lib/Target/PowerPC/Disassembler/PPCDisassembler.cpp
@@ -50,7 +50,7 @@ static MCDisassembler *createPPCLEDisassembler(const Target &T,
   return new PPCDisassembler(STI, Ctx, /*IsLittleEndian=*/true);
 }
 
-extern "C" void LLVMInitializePowerPCDisassembler() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializePowerPCDisassembler() {
   // Register the disassembler for each target.
   TargetRegistry::RegisterMCDisassembler(getThePPC32Target(),
                                          createPPCDisassembler);
diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCTargetDesc.cpp b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCTargetDesc.cpp
index 18bff4c7883..cbfb8e2ff28 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCTargetDesc.cpp
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCTargetDesc.cpp
@@ -292,7 +292,7 @@ static MCInstPrinter *createPPCMCInstPrinter(const Triple &T,
   return new PPCInstPrinter(MAI, MII, MRI, T);
 }
 
-extern "C" void LLVMInitializePowerPCTargetMC() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializePowerPCTargetMC() {
   for (Target *T :
        {&getThePPC32Target(), &getThePPC64Target(), &getThePPC64LETarget()}) {
     // Register the MC asm info.
diff --git a/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp b/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
index 0458f5a2548..4311df5dbeb 100644
--- a/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
+++ b/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
@@ -1801,7 +1801,7 @@ createPPCAsmPrinterPass(TargetMachine &tm,
 }
 
 // Force static initialization.
-extern "C" void LLVMInitializePowerPCAsmPrinter() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializePowerPCAsmPrinter() {
   TargetRegistry::RegisterAsmPrinter(getThePPC32Target(),
                                      createPPCAsmPrinterPass);
   TargetRegistry::RegisterAsmPrinter(getThePPC64Target(),
diff --git a/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp b/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
index 657fdcba1a4..2caf4c99a1f 100644
--- a/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
+++ b/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
@@ -94,7 +94,7 @@ static cl::opt<bool>
   ReduceCRLogical("ppc-reduce-cr-logicals",
                   cl::desc("Expand eligible cr-logical binary ops to branches"),
                   cl::init(true), cl::Hidden);
-extern "C" void LLVMInitializePowerPCTarget() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializePowerPCTarget() {
   // Register the targets
   RegisterTargetMachine<PPCTargetMachine> A(getThePPC32Target());
   RegisterTargetMachine<PPCTargetMachine> B(getThePPC64Target());
diff --git a/llvm/lib/Target/PowerPC/TargetInfo/PowerPCTargetInfo.cpp b/llvm/lib/Target/PowerPC/TargetInfo/PowerPCTargetInfo.cpp
index 99b5dec7466..649bd648a6c 100644
--- a/llvm/lib/Target/PowerPC/TargetInfo/PowerPCTargetInfo.cpp
+++ b/llvm/lib/Target/PowerPC/TargetInfo/PowerPCTargetInfo.cpp
@@ -23,7 +23,7 @@ Target &llvm::getThePPC64LETarget() {
   return ThePPC64LETarget;
 }
 
-extern "C" void LLVMInitializePowerPCTargetInfo() {
+extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializePowerPCTargetInfo() {
   RegisterTarget<Triple::ppc, /*HasJIT=*/true> X(getThePPC32Target(), "ppc32",
                                                  "PowerPC 32", "PPC");