Fix crash on XCore on unused inline in EmitTargetMetadata

EmitTargetMetadata passed to emitTargetMD a null pointer as returned
from GetGlobalValue, for an unused inline function which has been
removed from the module at that point.

A FIXME in CodeGenModule.cpp commented that the calling code in
EmitTargetMetadata should be moved into the one target that needs it
(XCore). A review comment agreed. So the calling loop has been moved
into the XCore subclass. The check for null is done in that loop.

Differential Revision: https://reviews.llvm.org/D77068

clang/lib/CodeGen/CodeGenModule.cpp

@@ -663,7 +663,7 @@ void CodeGenModule::Release() {
   if (!getCodeGenOpts().RecordCommandLine.empty())
     EmitCommandLineMetadata();
 
-  EmitTargetMetadata();
+  getTargetCodeGenInfo().emitTargetMetadata(*this, MangledDeclNames);
 
   EmitBackendOptionsMetadata(getCodeGenOpts());
 }
@@ -5791,21 +5791,6 @@ void CodeGenModule::EmitCommandLineMetadata() {
   CommandLineMetadata->addOperand(llvm::MDNode::get(Ctx, CommandLineNode));
 }
 
-void CodeGenModule::EmitTargetMetadata() {
-  // Warning, new MangledDeclNames may be appended within this loop.
-  // We rely on MapVector insertions adding new elements to the end
-  // of the container.
-  // FIXME: Move this loop into the one target that needs it, and only
-  // loop over those declarations for which we couldn't emit the target
-  // metadata when we emitted the declaration.
-  for (unsigned I = 0; I != MangledDeclNames.size(); ++I) {
-    auto Val = *(MangledDeclNames.begin() + I);
-    const Decl *D = Val.first.getDecl()->getMostRecentDecl();
-    llvm::GlobalValue *GV = GetGlobalValue(Val.second);
-    getTargetCodeGenInfo().emitTargetMD(D, GV, *this);
-  }
-}
-
 void CodeGenModule::EmitCoverageFile() {
   if (getCodeGenOpts().CoverageDataFile.empty() &&
       getCodeGenOpts().CoverageNotesFile.empty())

clang/lib/CodeGen/CodeGenModule.h

@@ -1532,9 +1532,6 @@ private:
   /// Emit the Clang commandline as llvm.commandline metadata.
   void EmitCommandLineMetadata();
 
-  /// Emits target specific Metadata for global declarations.
-  void EmitTargetMetadata();
-
   /// Emit the module flag metadata used to pass options controlling the
   /// the backend to LLVM.
   void EmitBackendOptionsMetadata(const CodeGenOptions CodeGenOpts);

clang/lib/CodeGen/TargetInfo.cpp

@@ -9535,11 +9535,15 @@ public:
 
 class XCoreTargetCodeGenInfo : public TargetCodeGenInfo {
   mutable TypeStringCache TSC;
+  void emitTargetMD(const Decl *D, llvm::GlobalValue *GV,
+                    const CodeGen::CodeGenModule &M) const;
+
 public:
   XCoreTargetCodeGenInfo(CodeGenTypes &CGT)
       : TargetCodeGenInfo(std::make_unique<XCoreABIInfo>(CGT)) {}
-  void emitTargetMD(const Decl *D, llvm::GlobalValue *GV,
-                    CodeGen::CodeGenModule &M) const override;
+  void emitTargetMetadata(CodeGen::CodeGenModule &CGM,
+                          const llvm::MapVector<GlobalDecl, StringRef>
+                              &MangledDeclNames) const override;
 };
 
 } // End anonymous namespace.
@@ -9700,11 +9704,13 @@ StringRef TypeStringCache::lookupStr(const IdentifierInfo *ID) {
 /// The output is tested by test/CodeGen/xcore-stringtype.c.
 ///
 static bool getTypeString(SmallStringEnc &Enc, const Decl *D,
-                          CodeGen::CodeGenModule &CGM, TypeStringCache &TSC);
+                          const CodeGen::CodeGenModule &CGM,
+                          TypeStringCache &TSC);
 
 /// XCore uses emitTargetMD to emit TypeString metadata for global symbols.
-void XCoreTargetCodeGenInfo::emitTargetMD(const Decl *D, llvm::GlobalValue *GV,
-                                          CodeGen::CodeGenModule &CGM) const {
+void XCoreTargetCodeGenInfo::emitTargetMD(
+    const Decl *D, llvm::GlobalValue *GV,
+    const CodeGen::CodeGenModule &CGM) const {
   SmallStringEnc Enc;
   if (getTypeString(Enc, D, CGM, TSC)) {
     llvm::LLVMContext &Ctx = CGM.getModule().getContext();
@@ -9716,6 +9722,21 @@ void XCoreTargetCodeGenInfo::emitTargetMD(const Decl *D, llvm::GlobalValue *GV,
   }
 }
 
+void XCoreTargetCodeGenInfo::emitTargetMetadata(
+    CodeGen::CodeGenModule &CGM,
+    const llvm::MapVector<GlobalDecl, StringRef> &MangledDeclNames) const {
+  // Warning, new MangledDeclNames may be appended within this loop.
+  // We rely on MapVector insertions adding new elements to the end
+  // of the container.
+  for (unsigned I = 0; I != MangledDeclNames.size(); ++I) {
+    auto Val = *(MangledDeclNames.begin() + I);
+    llvm::GlobalValue *GV = CGM.GetGlobalValue(Val.second);
+    if (GV) {
+      const Decl *D = Val.first.getDecl()->getMostRecentDecl();
+      emitTargetMD(D, GV, CGM);
+    }
+  }
+}
 //===----------------------------------------------------------------------===//
 // SPIR ABI Implementation
 //===----------------------------------------------------------------------===//
@@ -10049,7 +10070,8 @@ static bool appendType(SmallStringEnc &Enc, QualType QType,
 }
 
 static bool getTypeString(SmallStringEnc &Enc, const Decl *D,
-                          CodeGen::CodeGenModule &CGM, TypeStringCache &TSC) {
+                          const CodeGen::CodeGenModule &CGM,
+                          TypeStringCache &TSC) {
   if (!D)
     return false;
 

clang/lib/CodeGen/TargetInfo.h

@@ -57,10 +57,11 @@ public:
   virtual void setTargetAttributes(const Decl *D, llvm::GlobalValue *GV,
                                    CodeGen::CodeGenModule &M) const {}
 
-  /// emitTargetMD - Provides a convenient hook to handle extra
-  /// target-specific metadata for the given global.
-  virtual void emitTargetMD(const Decl *D, llvm::GlobalValue *GV,
-                            CodeGen::CodeGenModule &M) const {}
+  /// emitTargetMetadata - Provides a convenient hook to handle extra
+  /// target-specific metadata for the given globals.
+  virtual void emitTargetMetadata(
+      CodeGen::CodeGenModule &CGM,
+      const llvm::MapVector<GlobalDecl, StringRef> &MangledDeclNames) const {}
 
   /// Determines the size of struct _Unwind_Exception on this platform,
   /// in 8-bit units.  The Itanium ABI defines this as:

clang/test/CodeGen/xcore-unused-inline.c

@@ -0,0 +1,9 @@
+// REQUIRES: xcore-registered-target
+// RUN: %clang_cc1 -triple xcore-unknown-unknown -emit-llvm -o - %s
+
+// D77068 fixes a segmentation fault and assertion failure "Unexpected null
+// Value" in the case of an unused inline function, when targeting xcore. This
+// test verifies that clang does not crash and does not produce code for such a
+// function.
+
+inline void dead_function(void) {}