Fix logic for not emitting no-dead-strip for some

objects in llvm.used (thanks Anton).  Makes visible
the magic 'l' prefix for symbols on Darwin which are
to be passed through the assembler, then removed at
linktime (previously all references to this had been
hidden in the ObjC FE code, oh well).



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55973 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetAsmInfo.h

@@ -216,10 +216,15 @@ namespace llvm {
     const char *GlobalPrefix;             // Defaults to ""
 
     /// PrivateGlobalPrefix - This prefix is used for globals like constant
-    /// pool entries that are completely private to the .o file and should not
+    /// pool entries that are completely private to the .s file and should not
     /// have names in the .o file.  This is often "." or "L".
     const char *PrivateGlobalPrefix;      // Defaults to "."
     
+    /// LessPrivateGlobalPrefix - This prefix is used for some Objective C
+    /// metadata symbols that should be passed through the assembler but be
+    /// removed by the linker.  This is "l" on Darwin.
+    const char *LessPrivateGlobalPrefix;      // Defaults to ""
+    
     /// JumpTableSpecialLabelPrefix - If not null, a extra (dead) label is
     /// emitted before jump tables with the specified prefix.
     const char *JumpTableSpecialLabelPrefix;  // Default to null.
@@ -653,6 +658,9 @@ namespace llvm {
     const char *getPrivateGlobalPrefix() const {
       return PrivateGlobalPrefix;
     }
+    const char *getLessPrivateGlobalPrefix() const {
+      return LessPrivateGlobalPrefix;
+    }
     const char *getJumpTableSpecialLabelPrefix() const {
       return JumpTableSpecialLabelPrefix;
     }

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -452,7 +452,9 @@ const GlobalValue * AsmPrinter::findGlobalValue(const Constant *CV) {
 
 /// EmitLLVMUsedList - For targets that define a TAI::UsedDirective, mark each
 /// global in the specified llvm.used list as being used with this directive.
-/// Non-globals (i.e. internal linkage) should not be emitted.
+/// Internally linked data beginning with the PrivateGlobalPrefix or the
+/// LessPrivateGlobalPrefix does not have the directive emitted (this 
+/// occurs in ObjC metadata).
 void AsmPrinter::EmitLLVMUsedList(Constant *List) {
   const char *Directive = TAI->getUsedDirective();
 
@@ -462,7 +464,17 @@ void AsmPrinter::EmitLLVMUsedList(Constant *List) {
   
   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
     const GlobalValue *GV = findGlobalValue(InitList->getOperand(i));
-    if (GV && (!GV->hasInternalLinkage() || isa<Function>(GV))) {
+    if (GV) {
+      if (GV->hasInternalLinkage() && !isa<Function>(GV) &&
+          ((strlen(TAI->getPrivateGlobalPrefix()) != 0 &&
+            Mang->getValueName(GV)
+              .substr(0,strlen(TAI->getPrivateGlobalPrefix())) ==
+              TAI->getPrivateGlobalPrefix()) ||
+           (strlen(TAI->getLessPrivateGlobalPrefix()) != 0 &&
+            Mang->getValueName(GV)
+              .substr(0,strlen(TAI->getLessPrivateGlobalPrefix())) ==
+              TAI->getLessPrivateGlobalPrefix())))
+        continue;
       O << Directive;
       EmitConstantValueOnly(InitList->getOperand(i));
       O << '\n';

lib/Target/ARM/ARMTargetAsmInfo.cpp

@@ -62,6 +62,7 @@ ARMDarwinTargetAsmInfo::ARMDarwinTargetAsmInfo(const ARMTargetMachine &TM):
 
   GlobalPrefix = "_";
   PrivateGlobalPrefix = "L";
+  LessPrivateGlobalPrefix = "l";
   StringConstantPrefix = "\1LC";
   BSSSection = 0;                       // no BSS section
   ZeroDirective = "\t.space\t";

lib/Target/PowerPC/PPCTargetAsmInfo.cpp

@@ -38,6 +38,7 @@ PPCDarwinTargetAsmInfo::PPCDarwinTargetAsmInfo(const PPCTargetMachine &TM):
   CommentString = ";";
   GlobalPrefix = "_";
   PrivateGlobalPrefix = "L";
+  LessPrivateGlobalPrefix = "l";
   StringConstantPrefix = "\1LC";
   ConstantPoolSection = "\t.const\t";
   JumpTableDataSection = ".const";

lib/Target/TargetAsmInfo.cpp

@@ -50,6 +50,7 @@ TargetAsmInfo::TargetAsmInfo() :
   CommentString("#"),
   GlobalPrefix(""),
   PrivateGlobalPrefix("."),
+  LessPrivateGlobalPrefix(""),
   JumpTableSpecialLabelPrefix(0),
   GlobalVarAddrPrefix(""),
   GlobalVarAddrSuffix(""),

lib/Target/X86/X86TargetAsmInfo.cpp

@@ -136,6 +136,7 @@ X86DarwinTargetAsmInfo::X86DarwinTargetAsmInfo(const X86TargetMachine &TM):
     Data64bitsDirective = 0;       // we can't emit a 64-bit unit
   ZeroDirective = "\t.space\t";  // ".space N" emits N zeros.
   PrivateGlobalPrefix = "L";     // Marker for constant pool idxs
+  LessPrivateGlobalPrefix = "l";  // Marker for some ObjC metadata
   BSSSection = 0;                       // no BSS section.
   ZeroFillDirective = "\t.zerofill\t";  // Uses .zerofill
   if (DTM->getRelocationModel() != Reloc::Static)