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, 43 insertions, 0 deletions

diff --git a/lib/Target/ARM/MCTargetDesc/ARMMachORelocationInfo.cpp b/lib/Target/ARM/MCTargetDesc/ARMMachORelocationInfo.cpp
new file mode 100644
index 0000000..807c948
--- /dev/null
+++ b/lib/Target/ARM/MCTargetDesc/ARMMachORelocationInfo.cpp
@@ -0,0 +1,43 @@
+//===-- ARMMachORelocationInfo.cpp ----------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "MCTargetDesc/ARMMCTargetDesc.h"
+#include "ARMMCExpr.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCRelocationInfo.h"
+#include "llvm-c/Disassembler.h"
+
+using namespace llvm;
+using namespace object;
+
+namespace {
+class ARMMachORelocationInfo : public MCRelocationInfo {
+public:
+  ARMMachORelocationInfo(MCContext &Ctx) : MCRelocationInfo(Ctx) {}
+
+  const MCExpr *createExprForCAPIVariantKind(const MCExpr *SubExpr,
+                                             unsigned VariantKind) {
+    switch(VariantKind) {
+    case LLVMDisassembler_VariantKind_ARM_HI16:
+      return ARMMCExpr::CreateUpper16(SubExpr, Ctx);
+    case LLVMDisassembler_VariantKind_ARM_LO16:
+      return ARMMCExpr::CreateLower16(SubExpr, Ctx);
+    default:
+      return MCRelocationInfo::createExprForCAPIVariantKind(SubExpr,
+                                                            VariantKind);
+    }
+  }
+};
+} // End unnamed namespace
+
+/// createARMMachORelocationInfo - Construct an ARM Mach-O RelocationInfo.
+MCRelocationInfo *llvm::createARMMachORelocationInfo(MCContext &Ctx) {
+  return new ARMMachORelocationInfo(Ctx);
+}