COFF: Fix short import lib import name type bitshift

[martell]

Summary

llvm-readobj: Support short import objects from within an archive
The import magic was previous just checked against the archive as a whole

As per the PE COFF spec (section 8.3, Import Name Type)
Offset: 18 Size 2 bits Name: Type
Offset: 20 Size 3 bits Name: Name Type

Offset: 20 added based on 18+2

[majnemer]

llvm-readobj reads this field. perhaps we could have a testcase?

[martell]

In D23540#516191, @majnemer wrote:

llvm-readobj reads this field. perhaps we could have a testcase?

lld also uses it to determine stripping of the symbol names.
This is mostly why i686 was broken at link time

I will add a test case

[compnerd]

Please add a test case for llvm via llvm-readobj.

[martell]

llvm-readobj hello.lib

File: HELLO.dll
Format: COFF-x86-64
Arch: x86_64
AddressSize: 64bit

File: HELLO.dll
Format: COFF-x86-64
Arch: x86_64
AddressSize: 64bit

File: HELLO.dll
Format: COFF-x86-64
Arch: x86_64
AddressSize: 64bit

Error reading file: hello.lib: Unrecognized file type..

It seems that objdump does not know how to handle short import sections.
Are you sure it is being used?

[compnerd]

Yeah, it should be:

if (COFFImportFile *Import = dyn_cast<COFFImportFile>(&Binary))
  dumpCOFFImportFile(Import);

include/llvm/Support/COFF.h

     }
 
     ImportNameType getNameType() const {
-      return static_cast<ImportNameType>((TypeInfo & 0x1C) >> 3);
+      return static_cast<ImportNameType>((TypeInfo & 0x1C) >> 2);
     }
   };
 

test/tools/llvm-readobj/imports-mangle.test

+RUN: llvm-readobj --coff-imports %p/Inputs/imports.mangle.coff-x86_64 | FileCheck -check-prefix=X64  %s
+
+X64:      Name type: undecorate
+X64-NEXT:   Symbol: __imp_?sym4@@YAHH@Z
+X64-NEXT:   Symbol: ?sym4@@YAHH@Z
+
+X64:      Name type: noprefix
+X64-NEXT:   Symbol: __imp__sym3
+X64-NEXT:   Symbol: _sym3
+
+X64:      Name type: name
+X64-NEXT:   Symbol: __imp_sym1
+X64-NEXT:   Symbol: sym1
+
+X64:      Name type: ordinal
+X64-NEXT:   Symbol: __imp_sym2
+X64-NEXT:   Symbol: sym2

tools/llvm-readobj/llvm-readobj.cpp

     }
     if (ObjectFile *Obj = dyn_cast<ObjectFile>(&*ChildOrErr.get()))
       dumpObject(Obj);
+    else if (COFFImportFile *Import = dyn_cast<COFFImportFile>(&*ChildOrErr.get()))
+      dumpCOFFImportFile(Import);
     else
       reportError(Arc->getFileName(), readobj_error::unrecognized_file_format);
   }