Add support for tlsldm assembler operator to ARM target

The standard local dynamic model for TLS on ARM systems needs two 
relocations:
- R_ARM_TLS_LDM32 (module idx)
- R_ARM_TLS_LDO32 (offset of object from origin of module TLS block)
    
In GNU style assembler we use symbol(tlsldm) and symbol(tlsldo) to
produce these relocations.
    
llvm-mc for ARM supports symbol(tlsldo) but does not support symbol(tlsldm).
This patch wires up the existing symbol(tlsldm) to R_ARM_TLS_LDM32.
    
TLS for ARM is defined in Addenda to, and Errata in, the ABI for the
ARM Architecture
    
Differential Revision: https://reviews.llvm.org/D22461

llvm-svn: 275977

lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp

@@ -221,6 +221,9 @@ unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target,
       case MCSymbolRefExpr::VK_TLSDESC:
         Type = ELF::R_ARM_TLS_GOTDESC;
         break;
+      case MCSymbolRefExpr::VK_TLSLDM:
+        Type = ELF::R_ARM_TLS_LDM32;
+        break;
       case MCSymbolRefExpr::VK_ARM_TLSDESCSEQ:
         Type = ELF::R_ARM_TLS_DESCSEQ;
         break;

test/MC/ARM/symbol-variants.s

@@ -90,8 +90,14 @@ bl f05(plt)
 @CHECK: 68 R_ARM_PREL31 f26
 @CHECK: 6c R_ARM_PREL31 f27
 
+@ tlsldm
+.word f28(TLSLDM)
+.word f29(tlsldm)
+@CHECK: 70 R_ARM_TLS_LDM32 f28
+@CHECK: 74 R_ARM_TLS_LDM32 f29
+
 @ got_prel
-.word	f28(GOT_PREL) + (. - .Lsym)
-	ldr r3, =f29(GOT_PREL)
-@ CHECK: 70 R_ARM_GOT_PREL f28
-@ CHECK: 78 R_ARM_GOT_PREL f29
+.word	f30(GOT_PREL) + (. - .Lsym)
+	ldr r3, =f31(GOT_PREL)
+@ CHECK: 78 R_ARM_GOT_PREL f30
+@ CHECK: 80 R_ARM_GOT_PREL f31