[ARM] Create objdump subtarget from build attrs

Enable an ELFObjectFile to read the its arm build attributes to
produce a target triple with a specific ARM architecture.
llvm-objdump now uses this functionality to automatically produce
a more accurate target.

Differential Revision: https://reviews.llvm.org/D28769

llvm-svn: 292366

1 files changed, 19 insertions, 2 deletions

diff --git a/llvm/tools/llvm-objdump/llvm-objdump.cpp b/llvm/tools/llvm-objdump/llvm-objdump.cpp
index 8373f0ce3f1..6b8a43ea1bd 100644
--- a/llvm/tools/llvm-objdump/llvm-objdump.cpp
+++ b/llvm/tools/llvm-objdump/llvm-objdump.cpp
@@ -357,7 +357,16 @@ static const Target *getTarget(const ObjectFile *Obj = nullptr) {
   llvm::Triple TheTriple("unknown-unknown-unknown");
   if (TripleName.empty()) {
     if (Obj) {
-      TheTriple.setArch(Triple::ArchType(Obj->getArch()));
+      auto Arch = Obj->getArch();
+      TheTriple.setArch(Triple::ArchType(Arch));
+
+      // For ARM targets, try to use the build attributes to build determine
+      // the build target. Target features are also added, but later during
+      // disassembly.
+      if (Arch == Triple::arm || Arch == Triple::armeb) {
+        Obj->setARMSubArch(TheTriple);
+      }
+
       // TheTriple defaults to ELF, and COFF doesn't have an environment:
       // the best we can do here is indicate that it is mach-o.
       if (Obj->isMachO())
@@ -369,8 +378,16 @@ static const Target *getTarget(const ObjectFile *Obj = nullptr) {
           TheTriple.setTriple("thumbv7-windows");
       }
     }
-  } else
+  } else {
     TheTriple.setTriple(Triple::normalize(TripleName));
+    // Use the triple, but also try to combine with ARM build attributes.
+    if (Obj) {
+      auto Arch = Obj->getArch();
+      if (Arch == Triple::arm || Arch == Triple::armeb) {
+        Obj->setARMSubArch(TheTriple);
+      }
+    }
+  }
 
   // Get the target specific parser.
   std::string Error;