Add MCSymbolizer for symbolic/annotated disassembly.

This is a basic first step towards symbolization of disassembled
instructions. This used to be done using externally provided (C API)
callbacks. This patch introduces:
- the MCSymbolizer class, that mimics the same functions that were used
  in the X86 and ARM disassemblers to symbolize immediate operands and
  to annotate loads based off PC (for things like c string literals).
- the MCExternalSymbolizer class, which implements the old C API.
- the MCRelocationInfo class, which provides a way for targets to
  translate relocations (either object::RelocationRef, or disassembler
  C API VariantKinds) to MCExprs.
- the MCObjectSymbolizer class, which does symbolization using what it
  finds in an object::ObjectFile. This makes simple symbolization (with
  no fancy relocation stuff) work for all object formats!
- x86-64 Mach-O and ELF MCRelocationInfos.
- A basic ARM Mach-O MCRelocationInfo, that provides just enough to
  support the C API VariantKinds.

Most of what works in otool (the only user of the old symbolization API
that I know of) for x86-64 symbolic disassembly (-tvV) works, namely:
- symbol references: call _foo; jmp 15 <_foo+50>
- relocations:       call _foo-_bar; call _foo-4
- __cf?string:       leaq 193(%rip), %rax ## literal pool for "hello"
Stub support is the main missing part (because libObject doesn't know,
among other things, about mach-o indirect symbols).

As for the MCSymbolizer API, instead of relying on the disassemblers
to call the tryAdding* methods, maybe this could be done automagically
using InstrInfo? For instance, even though PC-relative LEAs are used
to get the address of string literals in a typical Mach-O file, a MOV
would be used in an ELF file. And right now, the explicit symbolization
only recognizes PC-relative LEAs. InstrInfo should have already have
most of what is needed to know what to symbolize, so this can
definitely be improved.

I'd also like to remove object::RelocationRef::getValueString (it seems
only used by relocation printing in objdump), as simply printing the
created MCExpr is definitely enough (and cleaner than string concats).



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182625 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 34 insertions, 0 deletions

diff --git a/include/llvm/Support/TargetRegistry.h b/include/llvm/Support/TargetRegistry.h
index e1f6706618..b4e380b344 100644
--- a/include/llvm/Support/TargetRegistry.h
+++ b/include/llvm/Support/TargetRegistry.h
@@ -41,6 +41,7 @@ namespace llvm {
   class MCRegisterInfo;
   class MCStreamer;
   class MCSubtargetInfo;
+  class MCRelocationInfo;
   class MCTargetAsmParser;
   class TargetMachine;
   class TargetOptions;
@@ -56,6 +57,8 @@ namespace llvm {
                                 MCAsmBackend *TAB,
                                 bool ShowInst);
 
+  MCRelocationInfo *createMCRelocationInfo(MCContext &Ctx);
+
   /// Target - Wrapper for Target specific information.
   ///
   /// For registration purposes, this is a POD type so that targets can be
@@ -127,6 +130,8 @@ namespace llvm {
                                              MCCodeEmitter *CE,
                                              MCAsmBackend *TAB,
                                              bool ShowInst);
+    typedef MCRelocationInfo *(*MCRelocationInfoCtorTy)(StringRef TT,
+                                                        MCContext &Ctx);
 
   private:
     /// Next - The next registered target in the linked list, maintained by the
@@ -206,6 +211,10 @@ namespace llvm {
     /// AsmStreamer, if registered (default = llvm::createAsmStreamer).
     AsmStreamerCtorTy AsmStreamerCtorFn;
 
+    /// MCRelocationInfoCtorFn - Construction function for this target's
+    /// MCRelocationInfo, if registered (default = llvm::createMCRelocationInfo)
+    MCRelocationInfoCtorTy MCRelocationInfoCtorFn;
+
   public:
     Target() : AsmStreamerCtorFn(llvm::createAsmStreamer) {}
 
@@ -433,6 +442,16 @@ namespace llvm {
                                useDwarfDirectory, InstPrint, CE, TAB, ShowInst);
     }
 
+    /// createMCRelocationInfo - Create a target specific MCRelocationInfo.
+    ///
+    /// \param TT The target triple.
+    /// \param Ctx The target context.
+    MCRelocationInfo *
+      createMCRelocationInfo(StringRef TT, MCContext &Ctx) const {
+      // MCRelocationInfoCtorFn defaults to createMCRelocationInfo
+      return MCRelocationInfoCtorFn(TT, Ctx);
+    }
+
     /// @}
   };
 
@@ -760,6 +779,21 @@ namespace llvm {
         T.AsmStreamerCtorFn = Fn;
     }
 
+    /// RegisterMCRelocationInfo - Register an MCRelocationInfo
+    /// implementation for the given target.
+    ///
+    /// Clients are responsible for ensuring that registration doesn't occur
+    /// while another thread is attempting to access the registry. Typically
+    /// this is done by initializing all targets at program startup.
+    ///
+    /// @param T - The target being registered.
+    /// @param Fn - A function to construct an MCRelocationInfo for the target.
+    static void RegisterMCRelocationInfo(Target &T,
+                                         Target::MCRelocationInfoCtorTy Fn) {
+      if (!T.MCRelocationInfoCtorFn)
+        T.MCRelocationInfoCtorFn = Fn;
+    }
+
     /// @}
   };