[JITLink][COFF] Stub implementation for IMAGE_COMDAT_SELECT_LARGEST.

[sunho]

Summary

This is a hack.

[sunho]

so hacky.

llvm/lib/ExecutionEngine/JITLink/COFFLinkGraphBuilder.cpp

Expected<Symbol *> COFFLinkGraphBuilder::createCOMDATExportRequest(
   case COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH:
   case COFF::IMAGE_COMDAT_SELECT_SAME_SIZE: {
     // FIXME: Implement size/content validation when LinkGraph is able to
     // handle this.
     L = Linkage::Weak;
     break;
   }
   case COFF::IMAGE_COMDAT_SELECT_LARGEST: {
-    // FIXME: Support IMAGE_COMDAT_SELECT_LARGEST when LinkGraph is able to
-    // handle this.
-    return make_error<JITLinkError>(
-        "IMAGE_COMDAT_SELECT_LARGEST is not supported.");
+    // FIXME: Support IMAGE_COMDAT_SELECT_LARGEST properly when LinkGraph is
+    // able to handle this.
+    L = Linkage::Weak;
+    LLVM_DEBUG({
+      dbgs() << "    " << SymIndex
+             << ": IMAGE_COMDAT_SELECT_LARGEST was used in section "
+             << Symbol.getSectionNumber() << "\n";
+    });
+    break;
   }
   case COFF::IMAGE_COMDAT_SELECT_NEWEST: {
     // Even link.exe doesn't support this selection properly.
     return make_error<JITLinkError>(
         "IMAGE_COMDAT_SELECT_NEWEST is not supported.");
   }
   default: {
     return make_error<JITLinkError>("Invalid comdat selection type: " +
LLVM_DEBUG({
     dbgs() << "      " << *Target << "\n";
   });
   PendingComdatExport = None;
   return Target;
 }
 
 } // namespace jitlink
 } // namespace llvm
 No newline at end of file

llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_largest.test

 # REQUIRES: asserts
-# XFAIL: *
 # RUN: yaml2obj %s -o %t
 # RUN: llvm-jitlink -noexec --debug-only=jitlink -noexec %t 2>&1
 # 
 # Check jitlink return an error when IMAGE_COMDAT_SELECT_LARGEST selection type is encountered.
 #
+# CHECK: Creating graph symbols...
+# CHECK:      2: Creating defined graph symbol for COFF symbol ".text" in .text (index: 2)
+# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: strong, scope: local, dead  -   <anonymous symbol>
+# CHECK-NEXT: 4: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
+# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: weak, scope: default, dead  -   func
 
 --- !COFF
 header:
   Machine:         IMAGE_FILE_MACHINE_AMD64
   Characteristics: [  ]
 sections:
   - Name:            .text
     Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]