Allow repeated registration again.

Our use of -fvisibility-inlines-hidden means we cannot check function pointers
against non null values.

Unfortunately, we also cannot assert that the callbacks are initialized only
once. The problem is that lldb has multiple subsystems that need to call this
and they don't have a unique initialization order.

Thanks to Sean Callanan for reporting it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192835 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/TargetRegistry.h

@@ -598,7 +598,6 @@ namespace llvm {
     /// @param T - The target being registered.
     /// @param Fn - A function to construct a MCAsmInfo for the target.
     static void RegisterMCAsmInfo(Target &T, Target::MCAsmInfoCtorFnTy Fn) {
-      assert(!T.MCAsmInfoCtorFn);
       T.MCAsmInfoCtorFn = Fn;
     }
 
@@ -613,7 +612,6 @@ namespace llvm {
     /// @param Fn - A function to construct a MCCodeGenInfo for the target.
     static void RegisterMCCodeGenInfo(Target &T,
                                      Target::MCCodeGenInfoCtorFnTy Fn) {
-      assert(!T.MCCodeGenInfoCtorFn);
       T.MCCodeGenInfoCtorFn = Fn;
     }
 
@@ -627,7 +625,6 @@ namespace llvm {
     /// @param T - The target being registered.
     /// @param Fn - A function to construct a MCInstrInfo for the target.
     static void RegisterMCInstrInfo(Target &T, Target::MCInstrInfoCtorFnTy Fn) {
-      assert(!T.MCInstrInfoCtorFn);
       T.MCInstrInfoCtorFn = Fn;
     }
 
@@ -635,7 +632,6 @@ namespace llvm {
     /// the given target.
     static void RegisterMCInstrAnalysis(Target &T,
                                         Target::MCInstrAnalysisCtorFnTy Fn) {
-      assert(!T.MCInstrAnalysisCtorFn);
       T.MCInstrAnalysisCtorFn = Fn;
     }
 
@@ -649,7 +645,6 @@ namespace llvm {
     /// @param T - The target being registered.
     /// @param Fn - A function to construct a MCRegisterInfo for the target.
     static void RegisterMCRegInfo(Target &T, Target::MCRegInfoCtorFnTy Fn) {
-      assert(!T.MCRegInfoCtorFn);
       T.MCRegInfoCtorFn = Fn;
     }
 
@@ -664,7 +659,6 @@ namespace llvm {
     /// @param Fn - A function to construct a MCSubtargetInfo for the target.
     static void RegisterMCSubtargetInfo(Target &T,
                                         Target::MCSubtargetInfoCtorFnTy Fn) {
-      assert(!T.MCSubtargetInfoCtorFn);
       T.MCSubtargetInfoCtorFn = Fn;
     }
 
@@ -679,7 +673,6 @@ namespace llvm {
     /// @param Fn - A function to construct a TargetMachine for the target.
     static void RegisterTargetMachine(Target &T,
                                       Target::TargetMachineCtorTy Fn) {
-      assert(!T.TargetMachineCtorFn);
       T.TargetMachineCtorFn = Fn;
     }
 
@@ -693,7 +686,6 @@ namespace llvm {
     /// @param T - The target being registered.
     /// @param Fn - A function to construct an AsmBackend for the target.
     static void RegisterMCAsmBackend(Target &T, Target::MCAsmBackendCtorTy Fn) {
-      assert(!T.MCAsmBackendCtorFn);
       T.MCAsmBackendCtorFn = Fn;
     }
 
@@ -707,7 +699,6 @@ namespace llvm {
     /// @param T - The target being registered.
     /// @param Fn - A function to construct an MCTargetAsmParser for the target.
     static void RegisterMCAsmParser(Target &T, Target::MCAsmParserCtorTy Fn) {
-      assert(!T.MCAsmParserCtorFn);
       T.MCAsmParserCtorFn = Fn;
     }
 
@@ -721,7 +712,6 @@ namespace llvm {
     /// @param T - The target being registered.
     /// @param Fn - A function to construct an AsmPrinter for the target.
     static void RegisterAsmPrinter(Target &T, Target::AsmPrinterCtorTy Fn) {
-      assert(!T.AsmPrinterCtorFn);
       T.AsmPrinterCtorFn = Fn;
     }
 
@@ -736,7 +726,6 @@ namespace llvm {
     /// @param Fn - A function to construct an MCDisassembler for the target.
     static void RegisterMCDisassembler(Target &T,
                                        Target::MCDisassemblerCtorTy Fn) {
-      assert(!T.MCDisassemblerCtorFn);
       T.MCDisassemblerCtorFn = Fn;
     }
 
@@ -751,7 +740,6 @@ namespace llvm {
     /// @param Fn - A function to construct an MCInstPrinter for the target.
     static void RegisterMCInstPrinter(Target &T,
                                       Target::MCInstPrinterCtorTy Fn) {
-      assert(!T.MCInstPrinterCtorFn);
       T.MCInstPrinterCtorFn = Fn;
     }
 
@@ -766,7 +754,6 @@ namespace llvm {
     /// @param Fn - A function to construct an MCCodeEmitter for the target.
     static void RegisterMCCodeEmitter(Target &T,
                                       Target::MCCodeEmitterCtorTy Fn) {
-      assert(!T.MCCodeEmitterCtorFn);
       T.MCCodeEmitterCtorFn = Fn;
     }
 
@@ -781,7 +768,6 @@ namespace llvm {
     /// @param Fn - A function to construct an MCStreamer for the target.
     static void RegisterMCObjectStreamer(Target &T,
                                          Target::MCObjectStreamerCtorTy Fn) {
-      assert(!T.MCObjectStreamerCtorFn);
       T.MCObjectStreamerCtorFn = Fn;
     }
 
@@ -795,7 +781,6 @@ namespace llvm {
     /// @param T - The target being registered.
     /// @param Fn - A function to construct an MCStreamer for the target.
     static void RegisterAsmStreamer(Target &T, Target::AsmStreamerCtorTy Fn) {
-      assert(!T.AsmStreamerCtorFn);
       T.AsmStreamerCtorFn = Fn;
     }
 
@@ -810,7 +795,6 @@ namespace llvm {
     /// @param Fn - A function to construct an MCRelocationInfo for the target.
     static void RegisterMCRelocationInfo(Target &T,
                                          Target::MCRelocationInfoCtorTy Fn) {
-      assert(!T.MCRelocationInfoCtorFn);
       T.MCRelocationInfoCtorFn = Fn;
     }
 
@@ -825,7 +809,6 @@ namespace llvm {
     /// @param Fn - A function to construct an MCSymbolizer for the target.
     static void RegisterMCSymbolizer(Target &T,
                                      Target::MCSymbolizerCtorTy Fn) {
-      assert(!T.MCSymbolizerCtorFn);
       T.MCSymbolizerCtorFn = Fn;
     }