[ARM][test] Test .long thumb_func - .

Commit 9746286 from 2011 is related to
a subtle case that is untested. GNU assembler produces an R_ARM_REL32
relocation.
We currently don't, therefore we have to add a workaround in MCExpr.cpp
to make the value odd (see commit 8ee6c0e "[MC] Remove isThumbFunc special case").

Author: MaskRay

llvm/test/MC/ARM/pcrel-global.s

@@ -1,9 +1,21 @@
 @ RUN: llvm-mc -filetype=obj -triple=armv7 %s -o %t
 @ RUN: llvm-readelf -r %t | FileCheck %s
+@ RUN: llvm-objdump -dr --triple=armv7 %t | FileCheck %s --check-prefix=DISASM
 @ RUN: llvm-mc -filetype=obj -triple=armebv7 %s -o %t
 @ RUN: llvm-readelf -r %t | FileCheck %s
 
 @ CHECK: There are no relocations in this file.
+
+@ DISASM-LABEL: <bar>:
+@ DISASM-NEXT:    adr.w   r0, #-4
+@ DISASM-NEXT:    adr.w   r0, #-8
+@ DISASM-NEXT:    ldr.w   pc, [pc, #-0xc]         @ 0x10 <bar>
+@ DISASM-NEXT:    ldr     r0, [pc, #0x0]          @ 0x20 <bar+0x10>
+@ DISASM-NEXT:    add     r0, pc
+@ DISASM-NEXT:   .word   0xffffffef
+@@ GNU assembler creates an R_ARM_REL32 referencing bar.
+@ DISASM-NOT:    {{.}}
+
 .syntax unified
 
 .globl foo
@@ -15,9 +27,16 @@ ldr r0, foo      @ arm_ldst_pcrel_12
 
 .thumb
 .thumb_func
-
+.type bar, %function
 .globl bar
 bar:
 adr r0, bar      @ thumb_adr_pcrel_10
 adr.w r0, bar    @ t2_adr_pcrel_12
 ldr.w pc, bar    @ t2_ldst_pcrel_12
+
+  ldr r0, .LCPI
+.LPC0_1:
+  add r0, pc
+
+.LCPI:
+  .long bar-(.LPC0_1+4)  @ if there is no relocation, the value should be odd