[llvm] Allow "[[FLAGS=<none>]]" value in the ELF Fileheader Flags field (PR #143845)

[James Henderson via llvm-commits]

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@@ -0,0 +1,48 @@
+## Test for FileHeader Flags; when FLAGS variable isn't defined, the e_flags value is 0, otherwise it's the specified value
+
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-readobj -h %t | FileCheck %s --check-prefixes=CHECK,NO-FLAG
+
+# RUN: yaml2obj %s -o %t -DFLAGS=[EF_AMDGPU_MACH_AMDGCN_GFX900]
+# RUN: llvm-readobj -h %t | FileCheck %s --check-prefixes=CHECK,FLAG
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  OSABI:           ELFOSABI_AMDGPU_HSA
+  Type:            ET_EXEC
+  Machine:         EM_AMDGPU
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jh7370 wrote:

I'd suggest we don't use `AMDGPU` here, because of the interactions with other fields and the extra complexities this introduces to the test that aren't necessary to demonstrate the important behaviour. Instead, I'd get rid of the `OSABI` field and pick a "simpler" machine like `EM_ARM`. You can then just pick one of the available ARM flags for the test, e.g. `EF_ARM_ABI_FLOAT_HARD`.

https://github.com/llvm/llvm-project/pull/143845