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/include/llvm/LinkAllPasses.h b/include/llvm/LinkAllPasses.h
index c2375eaab11a2628782575d135d34ed695711875..876703b90320bd5032fd7495557ca3faf4600d79 100644 (file)
--- a/include/llvm/LinkAllPasses.h
+++ b/include/llvm/LinkAllPasses.h
@@ -113,6 +113,7 @@ namespace {
       (void) llvm::createSingleLoopExtractorPass();
       (void) llvm::createStripSymbolsPass();
       (void) llvm::createStripNonDebugSymbolsPass();
+      (void) llvm::createStripDeadDebugInfoPass();
       (void) llvm::createStripDeadPrototypesPass();
       (void) llvm::createTailCallEliminationPass();
       (void) llvm::createTailDuplicationPass();

diff --git a/include/llvm/Transforms/IPO.h b/include/llvm/Transforms/IPO.h
index 5e179044229389608976f0381715e774f7afd09b..8fb4b63c64638f4a316ed7d40046322ee637cd92 100644 (file)
--- a/include/llvm/Transforms/IPO.h
+++ b/include/llvm/Transforms/IPO.h
@@ -44,6 +44,11 @@ ModulePass *createStripNonDebugSymbolsPass();
 // These pass removes llvm.dbg.declare intrinsics.
 ModulePass *createStripDebugDeclarePass();
 
+//===----------------------------------------------------------------------===//
+//
+// These pass removes unused symbols' debug info.
+ModulePass *createStripDeadDebugInfoPass();
+
 //===----------------------------------------------------------------------===//
 /// createLowerSetJmpPass - This function lowers the setjmp/longjmp intrinsics
 /// to invoke/unwind instructions.  This should really be part of the C/C++

diff --git a/lib/Transforms/IPO/StripSymbols.cpp b/lib/Transforms/IPO/StripSymbols.cpp
index 08ad4de429a0254543239dcb4b69a6ee80b3f92e..12e8db8b4a5463803c918d84aa5ee9a9387900ec 100644 (file)
--- a/lib/Transforms/IPO/StripSymbols.cpp
+++ b/lib/Transforms/IPO/StripSymbols.cpp
@@ -73,6 +73,19 @@ namespace {
       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 @@ ModulePass *llvm::createStripDebugDeclarePass() {
   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 @@ bool StripDebugDeclare::runOnModule(Module &M) {
 
   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;
+}

diff --git a/test/Transforms/StripSymbols/2010-07-01-DeadDbgInfo.ll b/test/Transforms/StripSymbols/2010-07-01-DeadDbgInfo.ll
new file mode 100644 (file)
index 0000000..721f0c8
--- /dev/null
+++ b/test/Transforms/StripSymbols/2010-07-01-DeadDbgInfo.ll
@@ -0,0 +1,47 @@
+; RUN: opt -strip-dead-debug-info | llvm-dis -o %t.ll
+; RUN: grep -v bar %t.ll
+; RUN: grep -v abcd %t.ll
+
+@xyz = global i32 2                               ; <i32*> [#uses=1]
+
+declare void @llvm.dbg.value(metadata, i64, metadata) nounwind readnone
+
+define i32 @fn() nounwind readnone ssp {
+entry:
+  ret i32 0, !dbg !17
+}
+
+define i32 @foo(i32 %i) nounwind readonly ssp {
+entry:
+  tail call void @llvm.dbg.value(metadata !{i32 %i}, i64 0, metadata !14), !dbg !19
+  %.0 = load i32* @xyz, align 4                   ; <i32> [#uses=1]
+  ret i32 %.0, !dbg !20
+}
+
+!llvm.dbg.sp = !{!0, !5, !9}
+!llvm.dbg.lv.bar = !{!12}
+!llvm.dbg.lv.foo = !{!14}
+!llvm.dbg.gv = !{!15, !16}
+
+!0 = metadata !{i32 524334, i32 0, metadata !1, metadata !"bar", metadata !"bar", metadata !"", metadata !1, i32 5, metadata !3, i1 true, i1 true, i32 0, i32 0, null, i1 false, i1 true, null} ; [ DW_TAG_subprogram ]
+!1 = metadata !{i32 524329, metadata !"g.c", metadata !"/tmp/", metadata !2} ; [ DW_TAG_file_type ]
+!2 = metadata !{i32 524305, i32 0, i32 1, metadata !"g.c", metadata !"/tmp/", metadata !"4.2.1 (Based on Apple Inc. build 5658) (LLVM build)", i1 true, i1 true, metadata !"", i32 0} ; [ DW_TAG_compile_unit ]
+!3 = metadata !{i32 524309, metadata !1, metadata !"", metadata !1, i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !4, i32 0, null} ; [ DW_TAG_subroutine_type ]
+!4 = metadata !{null}
+!5 = metadata !{i32 524334, i32 0, metadata !1, metadata !"fn", metadata !"fn", metadata !"fn", metadata !1, i32 6, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i1 false, i1 true, i32 ()* @fn} ; [ DW_TAG_subprogram ]
+!6 = metadata !{i32 524309, metadata !1, metadata !"", metadata !1, i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !7, i32 0, null} ; [ DW_TAG_subroutine_type ]
+!7 = metadata !{metadata !8}
+!8 = metadata !{i32 524324, metadata !1, metadata !"int", metadata !1, i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ]
+!9 = metadata !{i32 524334, i32 0, metadata !1, metadata !"foo", metadata !"foo", metadata !"foo", metadata !1, i32 7, metadata !10, i1 false, i1 true, i32 0, i32 0, null, i1 false, i1 true, i32 (i32)* @foo} ; [ DW_TAG_subprogram ]
+!10 = metadata !{i32 524309, metadata !1, metadata !"", metadata !1, i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !11, i32 0, null} ; [ DW_TAG_subroutine_type ]
+!11 = metadata !{metadata !8, metadata !8}
+!12 = metadata !{i32 524544, metadata !13, metadata !"bb", metadata !1, i32 5, metadata !8} ; [ DW_TAG_auto_variable ]
+!13 = metadata !{i32 524299, metadata !0, i32 5, i32 0} ; [ DW_TAG_lexical_block ]
+!14 = metadata !{i32 524545, metadata !9, metadata !"i", metadata !1, i32 7, metadata !8} ; [ DW_TAG_arg_variable ]
+!15 = metadata !{i32 524340, i32 0, metadata !1, metadata !"abcd", metadata !"abcd", metadata !"", metadata !1, i32 2, metadata !8, i1 true, i1 true, null} ; [ DW_TAG_variable ]
+!16 = metadata !{i32 524340, i32 0, metadata !1, metadata !"xyz", metadata !"xyz", metadata !"", metadata !1, i32 3, metadata !8, i1 false, i1 true, i32* @xyz} ; [ DW_TAG_variable ]
+!17 = metadata !{i32 6, i32 0, metadata !18, null}
+!18 = metadata !{i32 524299, metadata !5, i32 6, i32 0} ; [ DW_TAG_lexical_block ]
+!19 = metadata !{i32 7, i32 0, metadata !9, null}
+!20 = metadata !{i32 10, i32 0, metadata !21, null}
+!21 = metadata !{i32 524299, metadata !9, i32 7, i32 0} ; [ DW_TAG_lexical_block ]