Replace MCTargetOptionsCommandFlags.inc and CommandFlags.inc by runtime registration

MCTargetOptionsCommandFlags.inc and CommandFlags.inc are headers which contain
cl::opt with static storage.
These headers are meant to be incuded by tools to make it easier to parametrize
codegen/mc.

However, these headers are also included in at least two libraries: lldCommon
and handle-llvm. As a result, when creating DYLIB, clang-cpp holds a reference
to the options, and lldCommon holds another reference. Linking the two in a
single executable, as zig does[0], results in a double registration.

This patch explores an other approach: the .inc files are moved to regular
files, and the registration happens on-demand through static declaration of
options in the constructor of a static object.

[0] https://bugzilla.redhat.com/show_bug.cgi?id=1756977#c5

Differential Revision: https://reviews.llvm.org/D75579

1 files changed, 4 insertions, 2 deletions

diff --git a/llvm/tools/llvm-mc/llvm-mc.cpp b/llvm/tools/llvm-mc/llvm-mc.cpp
index dadb7f5..eee51a5 100644
--- a/llvm/tools/llvm-mc/llvm-mc.cpp
+++ b/llvm/tools/llvm-mc/llvm-mc.cpp
@@ -25,7 +25,7 @@
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSubtargetInfo.h"
-#include "llvm/MC/MCTargetOptionsCommandFlags.inc"
+#include "llvm/MC/MCTargetOptionsCommandFlags.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Compression.h"
 #include "llvm/Support/FileUtilities.h"
@@ -41,6 +41,8 @@
 
 using namespace llvm;
 
+static mc::RegisterMCTargetOptionsFlags MOF;
+
 static cl::opt<std::string>
 InputFilename(cl::Positional, cl::desc("<input file>"), cl::init("-"));
 
@@ -317,7 +319,7 @@ int main(int argc, char **argv) {
   cl::AddExtraVersionPrinter(TargetRegistry::printRegisteredTargetsForVersion);
 
   cl::ParseCommandLineOptions(argc, argv, "llvm machine code playground\n");
-  const MCTargetOptions MCOptions = InitMCTargetOptionsFromFlags();
+  const MCTargetOptions MCOptions = mc::InitMCTargetOptionsFromFlags();
   setDwarfDebugFlags(argc, argv);
 
   setDwarfDebugProducer();