[llvm-objdump] Add --reloc alias for -r (PR39407)

This addresses PR39407 (https://bugs.llvm.org/show_bug.cgi?id=39407)
improving compatibility with GNU binutils counterparts.

Reviewed By: kristina

Patch by Higuoxing (Xing).

Differential Revision: https://reviews.llvm.org/D53804

llvm-svn: 345703

llvm/test/tools/llvm-objdump/relocations-elf.test

@@ -0,0 +1,73 @@
+# RUN: yaml2obj %s > %t
+# RUN: llvm-objdump --reloc %t | FileCheck %s
+# RUN: llvm-objdump -r      %t | FileCheck %s
+
+# CHECK: RELOCATION RECORDS FOR [.rel.text]:
+# CHECK: 0000000000000001 R_X86_64_32 glob1
+# CHECK: 0000000000000001 R_X86_64_32S glob2
+# CHECK: 0000000000000002 R_X86_64_64 loc1
+
+# CHECK: RELOCATION RECORDS FOR [.rela.text]:
+# CHECK: 0000000000000001 R_X86_64_32 glob1+1
+# CHECK: 0000000000000001 R_X86_64_32S glob2+2
+# CHECK: 0000000000000002 R_X86_64_64 loc1+3
+
+!ELF
+FileHeader: !FileHeader
+  Class: ELFCLASS64
+  Data: ELFDATA2LSB
+  Type: ET_REL
+  Machine: EM_X86_64
+
+Sections:
+- Name: .text
+  Type: SHT_PROGBITS
+  Content: "0000000000000000"
+  AddressAlign: 16
+  Flags: [SHF_ALLOC]
+
+- Name: .rel.text
+  Type: SHT_REL
+  Info: .text
+  AddressAlign: 4
+  Relocations:
+    - Offset: 0x1
+      Symbol: glob1
+      Type: R_X86_64_32
+    - Offset: 0x1
+      Symbol: glob2
+      Type: R_X86_64_32S
+    - Offset: 0x2
+      Symbol: loc1
+      Type: R_X86_64_64
+
+- Name: .rela.text
+  Type: SHT_RELA
+  Link: .symtab
+  Info: .text
+  AddressAlign: 4
+  Relocations:
+    - Offset: 0x1
+      Addend: 1
+      Symbol: glob1
+      Type: R_X86_64_32
+    - Offset: 0x1
+      Addend: 2
+      Symbol: glob2
+      Type: R_X86_64_32S
+    - Offset: 0x2
+      Addend: 3
+      Symbol: loc1
+      Type: R_X86_64_64
+
+Symbols:
+  Local:
+    - Name: loc1
+    - Name: loc2
+  Global:
+    - Name: glob1
+      Section: .text
+      Value: 0x0
+      Size: 4
+    - Name: glob2
+

llvm/tools/llvm-objdump/llvm-objdump.cpp

@@ -106,7 +106,11 @@ DisassembleFunctions("df",
 static StringSet<> DisasmFuncsSet;
 
 cl::opt<bool>
-llvm::Relocations("r", cl::desc("Display the relocation entries in the file"));
+llvm::Relocations("reloc",
+                  cl::desc("Display the relocation entries in the file"));
+static cl::alias RelocationsShort("r", cl::desc("Alias for --reloc"),
+                                  cl::NotHidden,
+                                  cl::aliasopt(llvm::Relocations));
 
 cl::opt<bool>
 llvm::DynamicRelocations("dynamic-reloc",