[AArch64][AsmParser] Add MC support for %dtprel() relocation (llvm#186599)

This patch adds support for the %dtprel relocation specifier in the
AArch64 assembler. This specifier is used to generate the
R_AARCH64_TLS_DTPREL64 relocation, which is used in .debug_info sections
to describe the location of thread-local variables.

Prerequisite for  llvm#146572

Author: xgupta

llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp

@@ -4659,6 +4659,7 @@ bool AArch64AsmParser::parseSymbolicImmVal(const MCExpr *&ImmVal) {
                   .Case("prel_g1_nc", AArch64::S_PREL_G1_NC)
                   .Case("prel_g0", AArch64::S_PREL_G0)
                   .Case("prel_g0_nc", AArch64::S_PREL_G0_NC)
+                  .Case("dtprel", AArch64::S_DTPREL)
                   .Case("dtprel_g2", AArch64::S_DTPREL_G2)
                   .Case("dtprel_g1", AArch64::S_DTPREL_G1)
                   .Case("dtprel_g1_nc", AArch64::S_DTPREL_G1_NC)

llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFObjectWriter.cpp

@@ -249,6 +249,8 @@ unsigned AArch64ELFObjectWriter::getRelocType(const MCFixup &Fixup,
       }
       if (RefKind == AArch64::S_AUTH || RefKind == AArch64::S_AUTHADDR)
         return ELF::R_AARCH64_AUTH_ABS64;
+      if (RefKind == AArch64::S_DTPREL)
+        return ELF::R_AARCH64_TLS_DTPREL64;
       if (RefKind == AArch64::S_FUNCINIT)
         return ELF::R_AARCH64_FUNCINIT64;
       return ELF::R_AARCH64_ABS64;
@@ -465,6 +467,8 @@ unsigned AArch64ELFObjectWriter::getRelocType(const MCFixup &Fixup,
         return R_CLS(MOVW_PREL_G0);
       if (RefKind == AArch64::S_PREL_G0_NC)
         return R_CLS(MOVW_PREL_G0_NC);
+      if (RefKind == AArch64::S_DTPREL)
+        return ELF::R_AARCH64_TLS_DTPREL64;
       if (RefKind == AArch64::S_DTPREL_G2)
         return ELF::R_AARCH64_TLSLD_MOVW_DTPREL_G2;
       if (RefKind == AArch64::S_DTPREL_G1)

llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCAsmInfo.cpp

@@ -114,6 +114,7 @@ StringRef AArch64::getSpecifierName(AArch64::Specifier S) {
 
   case AArch64::S_GOTPCREL:            return "%gotpcrel";
   case AArch64::S_PLT:                 return "%pltpcrel";
+  case AArch64::S_DTPREL:              return "%dtprel";
   case AArch64::S_FUNCINIT:            return "%funcinit";
   default:
     llvm_unreachable("Invalid relocation specifier");
@@ -125,6 +126,7 @@ AArch64::Specifier AArch64::parsePercentSpecifierName(StringRef name) {
   return StringSwitch<AArch64::Specifier>(name)
       .Case("pltpcrel", AArch64::S_PLT)
       .Case("gotpcrel", AArch64::S_GOTPCREL)
+      .Case("dtprel", AArch64::S_DTPREL)
       .Case("funcinit", AArch64::S_FUNCINIT)
       .Default(0);
 }

llvm/test/MC/AArch64/tls-dtprel64.s

@@ -0,0 +1,27 @@
+// RUN: llvm-mc -triple=aarch64 -show-encoding < %s | FileCheck %s
+// RUN: llvm-mc -filetype=obj -triple=aarch64 %s | llvm-readobj -r - | FileCheck --check-prefix=CHECK-ELF %s
+
+# CHECK: .xword %dtprel(var)
+# CHECK: .xword	%dtprel(var+1)
+# CHECK: .xword	%dtprel(.tdata)
+# CHECK: .xword	%dtprel(.tdata+1)
+
+# CHECK-ELF: Relocations [
+# CHECK-ELF:   Section (5) .rela.debug_info {
+# CHECK-ELF:     0x0 R_AARCH64_TLS_DTPREL64 var 0x0
+# CHECK-ELF:     0x8 R_AARCH64_TLS_DTPREL64 var 0x1
+# CHECK-ELF:     0x10 R_AARCH64_TLS_DTPREL64 .tdata 0x0
+# CHECK-ELF:     0x18 R_AARCH64_TLS_DTPREL64 .tdata 0x1
+# CHECK-ELF:   }
+
+.section .tdata,"awT",@progbits
+.skip 8
+.globl var
+var:
+  .word 0
+
+.section        .debug_info,"",@progbits
+  .xword  %dtprel(var)
+  .xword  %dtprel(var+1)
+  .xword  %dtprel(.tdata)
+  .xword  %dtprel(.tdata+1)