DebugInfo/Symbolize: Exclude ARM mapping symbols for .symtab symbolization after D95916

Their names don't convey much information, so they should be excluded.
The behavior matches addr2line.

Differential Revision: https://reviews.llvm.org/D96617

Author: MaskRay

llvm/lib/DebugInfo/Symbolize/SymbolizableObjectFile.cpp

@@ -174,6 +174,11 @@ Error SymbolizableObjectFile::addSymbol(const SymbolRef &Symbol,
     if (Type != ELF::STT_NOTYPE && Type != ELF::STT_FUNC &&
         Type != ELF::STT_OBJECT && Type != ELF::STT_GNU_IFUNC)
       return Error::success();
+    // Some STT_NOTYPE symbols are not desired. This excludes STT_SECTION and
+    // ARM mapping symbols.
+    uint32_t Flags = cantFail(Symbol.getFlags());
+    if (Flags & SymbolRef::SF_FormatSpecific)
+      return Error::success();
   } else if (SymbolType != SymbolRef::ST_Function &&
              SymbolType != SymbolRef::ST_Data) {
     return Error::success();

llvm/test/DebugInfo/Symbolize/ELF/arm-mapping-symbol.s

@@ -0,0 +1,19 @@
+# REQUIRES: arm-registered-target
+## Ignore ARM mapping symbols (with a prefix of $a, $d or $t).
+
+# RUN: llvm-mc -filetype=obj -triple=armv7-none-linux %s -o %t
+# RUN: llvm-symbolizer --obj=%t 4 8 | FileCheck %s
+# RUN: llvm-mc -filetype=obj -triple=thumbv7-none-linux %s -o %tthumb
+# RUN: llvm-symbolizer --obj=%tthumb 4 8 | FileCheck %s
+
+# CHECK:       foo
+# CHECK-NEXT:  ??:0:0
+# CHECK-EMPTY:
+# CHECK-NEXT:  foo
+# CHECK-NEXT:  ??:0:0
+
+.globl foo
+foo:
+  .word 32
+  nop
+  .word 32