Debugging infomration is encoded in llvm IR using metadata. This is designed
such a way that debug info for symbols preserved even if symbols are
optimized away by the optimizer.
Add new special pass to remove debug info for such symbols.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107416 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/IPO/StripSymbols.cpp b/lib/Transforms/IPO/StripSymbols.cpp
index 08ad4de..12e8db8 100644
--- a/lib/Transforms/IPO/StripSymbols.cpp
+++ b/lib/Transforms/IPO/StripSymbols.cpp
@@ -73,6 +73,19 @@
AU.setPreservesAll();
}
};
+
+ class StripDeadDebugInfo : public ModulePass {
+ public:
+ static char ID; // Pass identification, replacement for typeid
+ explicit StripDeadDebugInfo()
+ : ModulePass(&ID) {}
+
+ virtual bool runOnModule(Module &M);
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesAll();
+ }
+ };
}
char StripSymbols::ID = 0;
@@ -99,6 +112,14 @@
return new StripDebugDeclare();
}
+char StripDeadDebugInfo::ID = 0;
+static RegisterPass<StripDeadDebugInfo>
+A("strip-dead-debug-info", "Strip debug info for unused symbols");
+
+ModulePass *llvm::createStripDeadDebugInfoPass() {
+ return new StripDeadDebugInfo();
+}
+
/// OnlyUsedBy - Return true if V is only used by Usr.
static bool OnlyUsedBy(Value *V, Value *Usr) {
for(Value::use_iterator I = V->use_begin(), E = V->use_end(); I != E; ++I) {
@@ -295,3 +316,83 @@
return true;
}
+
+/// getRealLinkageName - If special LLVM prefix that is used to inform the asm
+/// printer to not emit usual symbol prefix before the symbol name is used then
+/// return linkage name after skipping this special LLVM prefix.
+static StringRef getRealLinkageName(StringRef LinkageName) {
+ char One = '\1';
+ if (LinkageName.startswith(StringRef(&One, 1)))
+ return LinkageName.substr(1);
+ return LinkageName;
+}
+
+bool StripDeadDebugInfo::runOnModule(Module &M) {
+ bool Changed = false;
+
+ // Debugging infomration is encoded in llvm IR using metadata. This is designed
+ // such a way that debug info for symbols preserved even if symbols are
+ // optimized away by the optimizer. This special pass removes debug info for
+ // such symbols.
+
+ // llvm.dbg.gv keeps track of debug info for global variables.
+ if (NamedMDNode *NMD = M.getNamedMetadata("llvm.dbg.gv")) {
+ SmallVector<MDNode *, 8> MDs;
+ for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i)
+ if (DIGlobalVariable(NMD->getOperand(i)).Verify())
+ MDs.push_back(NMD->getOperand(i));
+ else
+ Changed = true;
+ NMD->eraseFromParent();
+ NMD = NULL;
+
+ for (SmallVector<MDNode *, 8>::iterator I = MDs.begin(),
+ E = MDs.end(); I != E; ++I) {
+ if (M.getGlobalVariable(DIGlobalVariable(*I).getGlobal()->getName(),
+ true)) {
+ if (!NMD)
+ NMD = M.getOrInsertNamedMetadata("llvm.dbg.gv");
+ NMD->addOperand(*I);
+ }
+ else
+ Changed = true;
+ }
+ }
+
+ // llvm.dbg.sp keeps track of debug info for subprograms.
+ if (NamedMDNode *NMD = M.getNamedMetadata("llvm.dbg.sp")) {
+ SmallVector<MDNode *, 8> MDs;
+ for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i)
+ if (DISubprogram(NMD->getOperand(i)).Verify())
+ MDs.push_back(NMD->getOperand(i));
+ else
+ Changed = true;
+ NMD->eraseFromParent();
+ NMD = NULL;
+
+ for (SmallVector<MDNode *, 8>::iterator I = MDs.begin(),
+ E = MDs.end(); I != E; ++I) {
+ bool FnIsLive = false;
+ if (Function *F = DISubprogram(*I).getFunction())
+ if (M.getFunction(F->getName()))
+ FnIsLive = true;
+ if (FnIsLive) {
+ if (!NMD)
+ NMD = M.getOrInsertNamedMetadata("llvm.dbg.sp");
+ NMD->addOperand(*I);
+ } else {
+ // Remove llvm.dbg.lv.fnname named mdnode which may have been used
+ // to hold debug info for dead function's local variables.
+ StringRef FName = DISubprogram(*I).getLinkageName();
+ if (FName.empty())
+ FName = DISubprogram(*I).getName();
+ if (NamedMDNode *LVNMD =
+ M.getNamedMetadata(Twine("llvm.dbg.lv.",
+ getRealLinkageName(FName))))
+ LVNMD->eraseFromParent();
+ }
+ }
+ }
+
+ return Changed;
+}