There's an issue with LLVM metadata support; it triggers an assert when trying

to generate asm for code with metadata globals.
This new pass is used as a workaround: it strips metadata from the module before
it reaches the code generator.
Obviously, this is disabled if LLVM doesn't support metadata.

gen/optimizer.cpp

@@ -50,6 +50,12 @@ disableGCToStack("disable-gc2stack",
     cl::desc("Disable promotion of GC allocations to stack memory in -O<N>"),
     cl::ZeroOrMore);
 
+// Not recommended; metadata currently triggers an assert in the backend...
+static cl::opt<bool>
+disableStripMetaData("disable-strip-metadata",
+    cl::desc("Disable default metadata stripping (not recommended)"),
+    cl::ZeroOrMore);
+
 static cl::opt<opts::BoolOrDefaultAdapter, false, opts::FlagParser>
 enableInlining("inlining",
     cl::desc("(*) Enable function inlining in -O<N>"),
@@ -137,6 +143,13 @@ static void addPassesForOptLevel(PassManager& pm) {
             pm.add(createCFGSimplificationPass());
         }
     }
+#ifdef USE_METADATA
+    if (!disableStripMetaData) {
+        // This one is purposely not disabled by disableLangSpecificPasses
+        // because the code generator will assert if it's not used.
+        pm.add(createStripMetaData());
+    }
+#endif
 
     // -O3
     if (optimizeLevel >= 3)
@@ -181,8 +194,18 @@ static void addPassesForOptLevel(PassManager& pm) {
 // Returns true if any optimization passes were invoked.
 bool ldc_optimize_module(llvm::Module* m)
 {
-    if (!optimize())
+    if (!optimize()) {
+#ifdef USE_METADATA
+        if (!disableStripMetaData) {
+            // This one always needs to run if metadata is generated, because
+            // the code generator will assert if it's not used.
+            ModulePass* stripMD = createStripMetaData();
+            stripMD->runOnModule(*m);
+            delete stripMD;
+        }
+#endif
         return false;
+    }
 
     PassManager pm;
     pm.add(new TargetData(m));

gen/passes/Passes.h

@@ -1,13 +1,19 @@
 #ifndef LDC_PASSES_H
 #define LDC_PASSES_H
 
+#include "gen/metadata.h"
 namespace llvm {
     class FunctionPass;
+    class ModulePass;
 }
 
 // Performs simplifications on runtime calls.
 llvm::FunctionPass* createSimplifyDRuntimeCalls();
 llvm::FunctionPass* createGarbageCollect2Stack();
 
+#ifdef USE_METADATA
+llvm::ModulePass *createStripMetaData();
+#endif
+
 
 #endif

gen/passes/StripMetaData.cpp

@@ -0,0 +1,85 @@
+//===- StripMetaData - Strips D-specific metadata -------------------------===//
+//
+//                             The LLVM D Compiler
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// There's an issue with the new LLVM metadata support; an assertion fires when
+// trying to generate asm for metadata globals.
+//
+// This pass is a workaround; it deletes the metadata LDC generates so the code
+// generator doesn't see it.
+// Obviously, this should only run after all passes that make use of that
+// metadata or they won't work.
+//
+//===----------------------------------------------------------------------===//
+
+#include "gen/metadata.h"
+
+// This pass isn't needed without metadata, so #ifdef it out entirely if the
+// LLVM version in use doesn't support it.
+#ifdef USE_METADATA
+
+
+#define DEBUG_TYPE "strip-metadata"
+
+#include "Passes.h"
+
+#include "llvm/Pass.h"
+#include "llvm/Module.h"
+#include "llvm/Constants.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+using namespace llvm;
+
+STATISTIC(NumDeleted, "Number of metadata globals deleted");
+
+//===----------------------------------------------------------------------===//
+// StripMetaData Pass Implementation
+//===----------------------------------------------------------------------===//
+
+namespace {
+    /// This pass optimizes library functions from the D runtime as used by LDC.
+    ///
+    class VISIBILITY_HIDDEN StripMetaData : public ModulePass {
+        public:
+        static char ID; // Pass identification
+        StripMetaData() : ModulePass(&ID) {}
+        
+        bool runOnModule(Module &M);
+    };
+    char StripMetaData::ID = 0;
+} // end anonymous namespace.
+
+static RegisterPass<StripMetaData>
+X("strip-metadata", "Delete D-specific metadata");
+
+// Public interface to the pass.
+ModulePass *createStripMetaData() {
+  return new StripMetaData(); 
+}
+
+/// runOnFunction - Top level algorithm.
+///
+bool StripMetaData::runOnModule(Module &M) {
+    bool Changed = false;
+    for (Module::global_iterator I = M.global_begin(), E = M.global_end(); I != E;) {
+        GlobalVariable* G = I++;
+        if (G->getNameLen() >= 9 && !strncmp(G->getNameStart(), "llvm.ldc.", 9)) {
+            assert(G->hasInitializer() && isa<MDNode>(G->getInitializer())
+                && "Not a metadata global?");
+            Changed = true;
+            NumDeleted++;
+            DEBUG(DOUT << "Deleting " << *G << '\n');
+            G->eraseFromParent();
+        }
+    }
+    return Changed;
+}
+
+
+#endif //USE_METADATA