[clang-offload-bundler] Do not add "llvm.used" to the .tgtsym section (#3896)

This patch changes clang-offload-bundler to skip special globals
llvm.used and llvm.compiler.used when collecting names of symbols
that are defined in the device object if it is a bitcode file.

Signed-off-by: Sergey Dmitriev <[email protected]>

Author: sndmitriev

clang/test/Driver/clang-offload-bundler-tgtsym.c

@@ -18,6 +18,9 @@
 // CHECK-DAG: sycl-spir64.bar
 // CHECK-NOT: undefined_func
 // CHECK-NOT: static_func
+// CHECK-NOT: static_used
+// CHECK-NOT: sycl-spir64.llvm.used
+// CHECK-NOT: sycl-spir64.llvm.compiler.used
 
 extern void undefined_func(void);
 
@@ -31,3 +34,6 @@ static void static_func(void) {}
 void bar(void) {
   static_func();
 }
+
+static void static_used(void) __attribute__((used));
+static void static_used() {}

clang/tools/clang-offload-bundler/ClangOffloadBundler.cpp

@@ -644,11 +644,19 @@ class ObjectFileHandler final : public FileHandler {
         if (Undefined || !Global)
           continue;
 
-        // Add symbol name with the target prefix to the buffer.
-        SymbolsOS << TargetNames[I] << ".";
-        if (Error Err = Symbol.printName(SymbolsOS))
+        // Get symbol name.
+        std::string Name;
+        raw_string_ostream NameOS(Name);
+        if (Error Err = Symbol.printName(NameOS))
           return std::move(Err);
-        SymbolsOS << '\0';
+
+        // If we are dealing with a bitcode file do not add special globals
+        // llvm.used and llvm.compiler.used to the list of defined symbols.
+        if (SF->isIR() && (Name == "llvm.used" || Name == "llvm.compiler.used"))
+          continue;
+
+        // Add symbol name with the target prefix to the buffer.
+        SymbolsOS << TargetNames[I] << "." << Name << '\0';
       }
     }
     return SymbolsBuf;