[llvm-objdump] Add the missing ARMv8 subarch detection

[MaskRay]

llvm/lib/Object/ELFObjectFile.cpp

360

Is "v8a" better?

There are a few other v8 build attributes:

v8_R     = 15,  // e.g. Cortex R52
v8_M_Base= 16,  // v8_M_Base AArch32
v8_M_Main= 17,  // v8_M_Main AArch32
v8_1_M_Main=21, // v8_1_M_Main AArch32

Should they be listed as well?

[kongyi]

I don't know what new instructions are introduced only in v8.1m-main, omitted the tests (it's not that interesting anyway).

llvm/lib/Object/ELFObjectFile.cpp

case ARMBuildAttrs::v6_M:
       Triple += "v6m";
       break;
     case ARMBuildAttrs::v6S_M:
       Triple += "v6sm";
       break;
     case ARMBuildAttrs::v7E_M:
       Triple += "v7em";
       break;
+    case ARMBuildAttrs::v8_A:
+      Triple += "v8";
+      break;
     }
   }
   if (!isLittleEndian())
     Triple += "eb";
 
   TheTriple.setArchName(Triple);
 }
 

llvm/test/tools/llvm-objdump/ARM/v8-subarch.s

+@ RUN: llvm-mc < %s -triple armv8-elf -filetype=obj | llvm-objdump -triple=arm -d - | FileCheck %s
+
+.arch armv8
+
+lda:
+lda r0, [r1]
+
+@ CHECK-LABEL:lda
+@ CHECK: 9f 0c 91 e1 lda r0, [r1]