[yaml2obj/obj2yaml] - Allow setting an arbitrary values for e_machine.

[grimar]

Summary

Currently we only allow using a known named constants
for Machine field in YAML documents.

This patch allows using any numbers (valid or "unknown")
and adds test cases for current and new functionality.

With this it is possible to write a test cases for really unknown
EM_* targets.

[jhenderson]

LGTM, with two minor suggestions.

test/tools/obj2yaml/elf-emachine.yaml

22 ↗

(On Diff #220469)

a enum -> an enum

test/tools/yaml2obj/elf-emachine.yaml

1 ↗

(On Diff #220469)

I'd rephrase this slightly:

"Test how the Machine YAML field can be used to set the e_machine ELF header field."

llvm/lib/ObjectYAML/ELFYAML.cpp

#define ECase(X) IO.enumCase(Value, #X, ELF::X)
   ECase(EM_VIDEOCORE5);
   ECase(EM_78KOR);
   ECase(EM_56800EX);
   ECase(EM_AMDGPU);
   ECase(EM_RISCV);
   ECase(EM_LANAI);
   ECase(EM_BPF);
 #undef ECase
+  IO.enumFallback<Hex16>(Value);
 }
 
 void ScalarEnumerationTraits<ELFYAML::ELF_ELFCLASS>::enumeration(
     IO &IO, ELFYAML::ELF_ELFCLASS &Value) {
 #define ECase(X) IO.enumCase(Value, #X, ELF::X)
   // Since the semantics of ELFCLASSNONE is "invalid", just don't accept it
   // here.
   ECase(ELFCLASS32);

llvm/test/tools/obj2yaml/elf-emachine.yaml

+## Check how obj2yaml dumps e_machine field.
+
+## Check it dumps an unknown e_machine as a number.
+
+# RUN: yaml2obj --docnum=1 %s -o %t1
+# RUN: obj2yaml %t1 | FileCheck %s --check-prefix=UNKNOWN
+
+# UNKNOWN:      --- !ELF
+# UNKNOWN-NEXT: FileHeader:
+# UNKNOWN-NEXT:   Class:   ELFCLASS64
+# UNKNOWN-NEXT:   Data:    ELFDATA2MSB
+# UNKNOWN-NEXT:   Type:    ET_REL
+# UNKNOWN-NEXT:   Machine: 0x1234
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2MSB
+  Type:    ET_REL
+  Machine: 0x1234
+
+## Check it dumps a known e_machine value as an enum string.
+
+# RUN: yaml2obj --docnum=2 %s -o %t2
+# RUN: obj2yaml %t2 | FileCheck %s --check-prefix=KNOWN
+
+# KNOWN:      --- !ELF
+# KNOWN-NEXT: FileHeader:
+# KNOWN-NEXT:   Class:   ELFCLASS64
+# KNOWN-NEXT:   Data:    ELFDATA2MSB
+# KNOWN-NEXT:   Type:    ET_REL
+# KNOWN-NEXT:   Machine: EM_NONE
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2MSB
+  Type:    ET_REL
+  Machine: 0

llvm/test/tools/yaml2obj/elf-emachine.yaml

+## Test how the Machine YAML field can be used to set the e_machine ELF header field.
+
+## Test we can use an arbitrary value.
+
+# RUN: yaml2obj --docnum=1 %s -o %t1
+# RUN: llvm-readelf %t1 --file-headers | FileCheck %s --check-prefix=UNKNOWN
+
+# UNKNOWN: Machine: 1234
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2MSB
+  Type:    ET_REL
+  Machine: 0x1234
+
+## Test we can't use a number that doesn't fit into 2 bytes.
+
+# RUN: not yaml2obj --docnum=2 %s 2>&1 | FileCheck %s --check-prefix=ERR
+
+# ERR: error: out of range hex16 number
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2MSB
+  Type:    ET_REL
+  Machine: 0x12345
+
+## Test we can use a known named constant.
+
+# RUN: yaml2obj --docnum=3 %s -o %t3
+# RUN: llvm-readelf %t3 --file-headers | FileCheck %s --check-prefix=NONE
+
+# NONE: Machine: None
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2MSB
+  Type:    ET_REL
+  Machine: EM_NONE
+
+## Test we can't use an unknown string constant.
+
+# RUN: not yaml2obj --docnum=4 %s 2>&1 | FileCheck %s --check-prefix=ERR2
+
+# ERR2: error: invalid hex16 number
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2MSB
+  Type:    ET_REL
+  Machine: EM_UNKNOWN_FOO