[yaml2obj] - Allow specifying custom Link values for SHT_HASH section.

This allows setting any sh_link values for SHT_HASH sections.

Differential revision: https://reviews.llvm.org/D68214

llvm-svn: 373316
diff --git a/llvm/lib/ObjectYAML/ELFEmitter.cpp b/llvm/lib/ObjectYAML/ELFEmitter.cpp
index 5acb02a..1651d60 100644
--- a/llvm/lib/ObjectYAML/ELFEmitter.cpp
+++ b/llvm/lib/ObjectYAML/ELFEmitter.cpp
@@ -821,7 +821,7 @@
       CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
 
   unsigned Link = 0;
-  if (SN2I.lookup(".dynsym", Link))
+  if (Section.Link.empty() && SN2I.lookup(".dynsym", Link))
     SHeader.sh_link = Link;
 
   if (Section.Content) {
diff --git a/llvm/test/tools/yaml2obj/elf-hash-section.yaml b/llvm/test/tools/yaml2obj/elf-hash-section.yaml
index 9995574..995c871 100644
--- a/llvm/test/tools/yaml2obj/elf-hash-section.yaml
+++ b/llvm/test/tools/yaml2obj/elf-hash-section.yaml
@@ -145,3 +145,35 @@
 Sections:
   - Name:  .hash
     Type:  SHT_HASH
+
+## Check we can set any sh_link value with use of the "Link" tag.
+
+# RUN: yaml2obj --docnum=8 %s -o %t8
+# RUN: llvm-readobj --sections %t8 | FileCheck %s --check-prefix=LINK
+
+# LINK:      Name: .hash1
+# LINK:      Link:
+# LINK-SAME: 123
+
+# LINK:      Name: .hash2
+# LINK:      Link:
+# LINK-SAME: 1
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS32
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_386
+Sections:
+  - Name: .hash1
+    Type: SHT_HASH
+    Content: ""
+    Link: 123
+  - Name: .hash2
+    Type: SHT_HASH
+    Content: ""
+    Link: .hash1
+## SHT_HASH is linked to dynamic symbol table by default if it exists.
+  - Name: .dynsym
+    Type: SHT_DYNSYM