[llvm] [z/OS] Add z/OS archive reading support (PR #187110)

[zhijian lin via llvm-commits]

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@@ -1042,6 +1170,14 @@ Expected<Archive::Child> Archive::Symbol::getMember() const {
     // the archive of the member that defines the symbol.  Which is what
     // is needed here.
     Offset = read64le(Offsets + SymbolIndex * 16 + 8);
+  } else if (Parent->kind() == K_ZOS) {
+    // The contents of the symbol table member in order are:
+    // 1. The number of symbols, NS (4 byte integer).
+    // 2. NS pairs of integers (the first in each pair of integers is the offset
+    //    to the header of the entry... the second being coded attributes).
+    //    Length is NS*(4+4) bytes.
+    // 3. NS null terminated strings of corresponding symbol names.
+    Offset = read32be(Offsets + SymbolIndex * 8);
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diggerlin wrote:

I think the comment you add here is not precise , you need to explain why it is *8. 

https://github.com/llvm/llvm-project/pull/187110