[clang] [llvm] [MC,llvm-readobj,yaml2obj] Support CREL relocation format (PR #91280)

[Fangrui Song via cfe-commits]

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@@ -86,6 +86,8 @@ DYNAMIC_TAG(RELRSZ, 35)  // Size of Relr relocation table.
 DYNAMIC_TAG(RELR, 36)    // Address of relocation table (Relr entries).
 DYNAMIC_TAG(RELRENT, 37) // Size of a Relr relocation entry.
 
+DYNAMIC_TAG(CREL,  38)   // CREL relocation table
+
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MaskRay wrote:

The commit message mentions:

> Without linker/dynamic loader concern, there is even less concern for people unintentionally using this.

I tentatively think it is not worth the trouble to avoid the generic range.

> Although not strictly necessary a CREL Size (CRELSZ?) could be useful for a consumer to read all the CRELs into memory without having to read the header first to find the size. Again not worth doing unless we have a definite need for it.

I've thought about this but believe CRELSZ is not so necessary.

https://github.com/llvm/llvm-project/pull/91280