ELF: accept -m elf_amd64 as an alias for -m elf_x86_64

[emaste]

Summary

In the FreeBSD world x86_64 still has its original name, amd64. Accept it as an alias.

Issue encountered while trying to link the FreeBSD kernel (modules) with lld, with D24060 and a build patch to always set -m (https://reviews.freebsd.org/D7837).

[davide]

I think this is OK.

[ruiu]

test/ELF/emulation.s

32–34

Instead of adding "AMD64:" lines, can you reuse exiting "X86-64"? I think the output will be the same.

[emaste]

test/ELF/emulation.s

32–34

It's not completely identical -- note the OS/ABI. Right now I could probably change the triple=x86_64-unknown-freebsd to -triple=x86_64-unknown-linux and switch to elf_amd64 from elf_amd64_fbsd, and then reuse the X86-64 lines.

However, as the amd64 case is somewhat FreeBSD-specific I'd prefer to leave the FreeBSDisms in this test case and leave it as elf_amd64_fbsd.

[ruiu]

Makes sense. LGTM.

ELF/Driver.cpp

std::pair<ELFKind, uint16_t> Ret =
           .Case("armelf_linux_eabi", {ELF32LEKind, EM_ARM})
           .Case("elf32_x86_64", {ELF32LEKind, EM_X86_64})
           .Case("elf32btsmip", {ELF32BEKind, EM_MIPS})
           .Case("elf32ltsmip", {ELF32LEKind, EM_MIPS})
           .Case("elf32ppc", {ELF32BEKind, EM_PPC})
           .Case("elf64btsmip", {ELF64BEKind, EM_MIPS})
           .Case("elf64ltsmip", {ELF64LEKind, EM_MIPS})
           .Case("elf64ppc", {ELF64BEKind, EM_PPC64})
+          .Case("elf_amd64", {ELF64LEKind, EM_X86_64})
           .Case("elf_i386", {ELF32LEKind, EM_386})
           .Case("elf_iamcu", {ELF32LEKind, EM_IAMCU})
           .Case("elf_x86_64", {ELF64LEKind, EM_X86_64})
           .Default({ELFNoneKind, EM_NONE});
 
   if (Ret.first == ELFNoneKind) {
     if (S == "i386pe" || S == "i386pep" || S == "thumb2pe")
       error("Windows targets are not supported on the ELF frontend: " + Emul);

test/ELF/emulation.s

+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-freebsd %s -o %tx64
+# RUN: ld.lld -m elf_amd64_fbsd %tx64 -o %t2x64
+# RUN: llvm-readobj -file-headers %t2x64 | FileCheck --check-prefix=AMD64 %s
+# RUN: ld.lld %tx64 -o %t3x64
+# RUN: llvm-readobj -file-headers %t3x64 | FileCheck --check-prefix=AMD64 %s
+# AMD64:      ElfHeader {
+# AMD64-NEXT:   Ident {
+# AMD64-NEXT:     Magic: (7F 45 4C 46)
+# AMD64-NEXT:     Class: 64-bit (0x2)
+# AMD64-NEXT:     DataEncoding: LittleEndian (0x1)
+# AMD64-NEXT:     FileVersion: 1
+# AMD64-NEXT:     OS/ABI: FreeBSD (0x9)
+# AMD64-NEXT:     ABIVersion: 0
+# AMD64-NEXT:     Unused: (00 00 00 00 00 00 00)
+# AMD64-NEXT:   }
+# AMD64-NEXT:   Type: Executable (0x2)
+# AMD64-NEXT:   Machine: EM_X86_64 (0x3E)
+# AMD64-NEXT:   Version: 1
+# AMD64-NEXT:   Entry:
+# AMD64-NEXT:   ProgramHeaderOffset: 0x40
+# AMD64-NEXT:   SectionHeaderOffset:
+# AMD64-NEXT:   Flags [ (0x0)
+# AMD64-NEXT:   ]
+# AMD64-NEXT:   HeaderSize: 64
+# AMD64-NEXT:   ProgramHeaderEntrySize: 56
+# AMD64-NEXT:   ProgramHeaderCount:
+# AMD64-NEXT:   SectionHeaderEntrySize: 64
+# AMD64-NEXT:   SectionHeaderCount:
+# AMD64-NEXT:   StringTableSectionIndex:
+# AMD64-NEXT: }
+
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %tx64
 # RUN: ld.lld -m elf_x86_64 %tx64 -o %t2x64
 # RUN: llvm-readobj -file-headers %t2x64 | FileCheck --check-prefix=X86-64 %s
 # RUN: ld.lld %tx64 -o %t3x64
 # RUN: llvm-readobj -file-headers %t3x64 | FileCheck --check-prefix=X86-64 %s
 # X86-64:      ElfHeader {
 # X86-64-NEXT:   Ident {
 # X86-64-NEXT:     Magic: (7F 45 4C 46)
 # X86-64-NEXT:     Class: 64-bit (0x2)
 # X86-64-NEXT:     DataEncoding: LittleEndian (0x1)
 # X86-64-NEXT:     FileVersion: 1