[lld] Introduce registry and Reference kind tuple

The main changes are in:
  include/lld/Core/Reference.h
  include/lld/ReaderWriter/Reader.h
Everything else is details to support the main change.

1) Registration based Readers
Previously, lld had a tangled interdependency with all the Readers.  It would
have been impossible to make a streamlined linker (say for a JIT) which
just supported one file format and one architecture (no yaml, no archives, etc).
The old model also required a LinkingContext to read an object file, which
would have made .o inspection tools awkward.

The new model is that there is a global Registry object. You programmatically 
register the Readers you want with the registry object. Whenever you need to 
read/parse a file, you ask the registry to do it, and the registry tries each 
registered reader.

For ease of use with the existing lld code base, there is one Registry
object inside the LinkingContext object. 


2) Changing kind value to be a tuple
Beside Readers, the registry also keeps track of the mapping for Reference
Kind values to and from strings.  Along with that, this patch also fixes
an ambiguity with the previous Reference::Kind values.  The problem was that
we wanted to reuse existing relocation type values as Reference::Kind values.
But then how can the YAML write know how to convert a value to a string? The
fix is to change the 32-bit Reference::Kind into a tuple with an 8-bit namespace
(e.g. ELF, COFFF, etc), an 8-bit architecture (e.g. x86_64, PowerPC, etc), and
a 16-bit value.  This tuple system allows conversion to and from strings with 
no ambiguities.

llvm-svn: 197727

1 files changed, 19 insertions, 56 deletions

diff --git a/lld/lib/ReaderWriter/CoreLinkingContext.cpp b/lld/lib/ReaderWriter/CoreLinkingContext.cpp
index 9132748f206..0d4fb993445 100644
--- a/lld/lib/ReaderWriter/CoreLinkingContext.cpp
+++ b/lld/lib/ReaderWriter/CoreLinkingContext.cpp
@@ -12,7 +12,6 @@
 #include "lld/Core/Pass.h"
 #include "lld/Core/PassManager.h"
 #include "lld/Passes/LayoutPass.h"
-#include "lld/Passes/RoundTripNativePass.h"
 #include "lld/Passes/RoundTripYAMLPass.h"
 #include "lld/ReaderWriter/Simple.h"
 
@@ -155,7 +154,7 @@ private:
 class TestingPassFile : public SimpleFile {
 public:
   TestingPassFile(const LinkingContext &ctx)
-      : SimpleFile(ctx, "Testing pass") {}
+      : SimpleFile("Testing pass") {}
 
   virtual void addAtom(const Atom &atom) {
     if (const DefinedAtom *defAtom = dyn_cast<DefinedAtom>(&atom))
@@ -189,25 +188,6 @@ private:
   atom_collection_vector<AbsoluteAtom> _absoluteAtoms;
 };
 
-struct TestingKindMapping {
-  const char *string;
-  int32_t value;
-  bool isBranch;
-  bool isGotLoad;
-  bool isGotUse;
-};
-
-//
-// Table of fixup kinds in YAML documents used for testing
-//
-const TestingKindMapping sKinds[] = {
-  { "in-group", -3, false, false, false },
-  { "layout-after", -2, false, false, false },
-  { "layout-before", -1, false, false, false },
-  { "call32", 2, true, false, false }, { "pcrel32", 3, false, false, false },
-  { "gotLoad32", 7, false, true, true }, { "gotUse32", 9, false, false, true },
-  { "lea32wasGot", 8, false, false, false }, { nullptr, 0, false, false, false }
-};
 
 class TestingStubsPass : public StubsPass {
 public:
@@ -215,12 +195,10 @@ public:
 
   virtual bool noTextRelocs() { return true; }
 
-  virtual bool isCallSite(int32_t kind) {
-    for (const TestingKindMapping *p = sKinds; p->string != nullptr; ++p) {
-      if (kind == p->value)
-        return p->isBranch;
-    }
-    return false;
+  virtual bool isCallSite(const Reference &ref) {
+    if (ref.kindNamespace() != Reference::KindNamespace::testing)
+      return false;
+    return (ref.kindValue() == CoreLinkingContext::TEST_RELOC_CALL32);
   }
 
   virtual const DefinedAtom *getStub(const Atom &target) {
@@ -245,22 +223,25 @@ public:
 
   virtual bool noTextRelocs() { return true; }
 
-  virtual bool isGOTAccess(int32_t kind, bool &canBypassGOT) {
-    for (const TestingKindMapping *p = sKinds; p->string != nullptr; ++p) {
-      if (kind == p->value) {
-        canBypassGOT = p->isGotLoad;
-        return p->isGotUse || p->isGotLoad;
-      }
+  virtual bool isGOTAccess(const Reference &ref, bool &canBypassGOT) {
+    if (ref.kindNamespace() != Reference::KindNamespace::testing)
+      return false;
+    switch (ref.kindValue()) {
+    case CoreLinkingContext::TEST_RELOC_GOT_LOAD32:
+      canBypassGOT = true;
+      return true;
+    case CoreLinkingContext::TEST_RELOC_GOT_USE32:
+      canBypassGOT = false;
+      return true;
     }
     return false;
   }
 
   virtual void updateReferenceToGOT(const Reference *ref, bool targetIsNowGOT) {
-    if (targetIsNowGOT)
-      const_cast<Reference *>(ref)->setKind(3); // pcrel32
-    else
-      const_cast<Reference *>(ref)->setKind(8); // lea32wasGot
-  }
+    const_cast<Reference *>(ref)->setKindValue(targetIsNowGOT ?
+                                  CoreLinkingContext::TEST_RELOC_PCREL32 : 
+                                  CoreLinkingContext::TEST_RELOC_LEA32_WAS_GOT);
+   }
 
   virtual const DefinedAtom *makeGOTEntry(const Atom &target) {
     return new TestingGOTAtom(_file, target);
@@ -275,7 +256,6 @@ private:
 CoreLinkingContext::CoreLinkingContext() {}
 
 bool CoreLinkingContext::validateImpl(raw_ostream &) {
-  _reader = createReaderYAML(*this);
   _writer = createWriterYAML(*this);
   return true;
 }
@@ -295,20 +275,3 @@ void CoreLinkingContext::addPasses(PassManager &pm) {
 
 Writer &CoreLinkingContext::writer() const { return *_writer; }
 
-ErrorOr<Reference::Kind>
-CoreLinkingContext::relocKindFromString(StringRef str) const {
-  for (const TestingKindMapping *p = sKinds; p->string != nullptr; ++p) {
-    if (str.equals(p->string))
-      return p->value;
-  }
-  return make_error_code(YamlReaderError::illegal_value);
-}
-
-ErrorOr<std::string>
-CoreLinkingContext::stringFromRelocKind(Reference::Kind kind) const {
-  for (const TestingKindMapping *p = sKinds; p->string != nullptr; ++p) {
-    if (kind == p->value)
-      return std::string(p->string);
-  }
-  return make_error_code(YamlReaderError::illegal_value);
-}