[StackMaps] Add a lightweight parser for stackmap version 1 sections.

The parser provides a convenient interface for reading llvm stackmap v1 sections
in object files.

This patch also includes a new option for llvm-readobj, '-stackmap', which uses
the parser to pretty-print stackmap sections for debugging/testing purposes.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240860 91177308-0d34-0410-b5e6-96231b3b80d8

tools/llvm-readobj/MachODumper.cpp

@@ -14,6 +14,7 @@
 #include "llvm-readobj.h"
 #include "Error.h"
 #include "ObjDumper.h"
+#include "StackMapPrinter.h"
 #include "StreamWriter.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"
@@ -37,6 +38,7 @@ public:
   void printSymbols() override;
   void printDynamicSymbols() override;
   void printUnwindInfo() override;
+  void printStackMap() const override;
 
 private:
   template<class MachHeader>
@@ -573,3 +575,32 @@ void MachODumper::printSymbol(const SymbolRef &Symbol) {
 void MachODumper::printUnwindInfo() {
   W.startLine() << "UnwindInfo not implemented.\n";
 }
+
+void MachODumper::printStackMap() const {
+  object::SectionRef StackMapSection;
+  for (auto Sec : Obj->sections()) {
+    StringRef Name;
+    Sec.getName(Name);
+    if (Name == "__llvm_stackmaps") {
+      StackMapSection = Sec;
+      break;
+    }
+  }
+
+  if (StackMapSection == object::SectionRef())
+    return;
+
+  StringRef StackMapContents;
+  StackMapSection.getContents(StackMapContents);
+  ArrayRef<uint8_t> StackMapContentsArray(
+      reinterpret_cast<const uint8_t*>(StackMapContents.data()),
+      StackMapContents.size());
+
+  if (Obj->isLittleEndian())
+     prettyPrintStackMap(
+                      llvm::outs(),
+                      StackMapV1Parser<support::little>(StackMapContentsArray));
+  else
+     prettyPrintStackMap(llvm::outs(),
+                         StackMapV1Parser<support::big>(StackMapContentsArray));
+}