[ELF] Test undefined weak symbol for Thumb narrow branch

Add a test for the R_ARM_THM_JUMP11 relocation to an undefined symbol. We
have to use yaml2obj as llvm-mc relaxes the narrow branch to a b.w which
uses the R_ARM_THM_JUMP24 relocation instead.
    
Differential Revision: https://reviews.llvm.org/D50234

llvm-svn: 338999

lld/test/ELF/arm-thumb-undefined-weak-narrow.test

@@ -0,0 +1,50 @@
+# REQUIRES: arm
+# RUN: yaml2obj %s -o %t.o
+# RUN: ld.lld %t.o -o %t
+# RUN: llvm-objdump -triple=thumbv7a-linux-gnueabi -d %t | FileCheck %s
+
+# CHECK: Disassembly of section .text:
+# CHECK-NEXT:_start:
+# CHECK-NEXT:    11000:       ff e7   b       #-2
+
+# Test the R_ARM_THM_JUMP11 relocation (102) to an undefined weak reference
+# It should resolve to the next instruction, which is an offset of -2 which
+# when added to the Thumb PC-bias of 4 is +2. We can't use llvm-mc to construct
+# the object as it relaxes b.n to b.w (R_ARM_JUMP24).
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS32
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_ARM
+Sections:
+  - Type:            SHT_PROGBITS
+    Name:            .text
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Content:         "fee7"
+  - Type:            SHT_REL
+    Name:            .rel.text
+    Link:            .symtab
+    Info:            .text
+    Relocations:
+      - Offset:          0
+        Symbol:          undefined_weak
+        Type:            R_ARM_THM_JUMP11
+
+Symbols:
+ Global:
+   - Type:             STT_FUNC
+     Name:             _start
+     Value:            1
+     Section:          .text
+ Local:
+   - Type:             STT_NOTYPE
+     Name:             "$t"
+     Section:          .text
+     Value:            0
+ Weak:
+   - Type:             STT_NOTYPE
+     Name:             undefined_weak
+     Value:            0
+