[mips] Fix TestDWARF32Version5Addr8AllForms test failure on MIPS hosts

The `DIEExpr` is used in debug information entries for either TLS variables
or call sites. For now the last case is unsupported for targets with delay
slots, for MIPS in particular.

The `DIEExpr::EmitValue` method calls a virtual `EmitDebugThreadLocal`
routine which, in case of MIPS, always emits either `.dtprelword` or
`.dtpreldword` directives. That is okay for "main" code, but in unit
tests `DIEExpr` instances can be created not for TLS variables only even
on MIPS hosts. That is a reason of the `TestDWARF32Version5Addr8AllForms`
failure because handling of the `R_MIPS_TLS_DTPREL` relocation writes
incorrect value into dwarf structures. And anyway unconditional emitting
of `.dtprelword` directives will be incorrect when/if debug information
entries for call sites become supported on MIPS.

The patch solves the problem by wrapping expression created in the
`MipsTargetObjectFile::getDebugThreadLocalSymbol` method in to the
`MipsMCExpr` expression with a new `MEK_DTPREL` tag. This tag is
recognized in the `MipsAsmPrinter::EmitDebugThreadLocal` method and
`.dtprelword` directives created in this case only. In other cases the
expression saved as a regular data.

Differential Revision: http://reviews.llvm.org/D54937

llvm-svn: 348194

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Target/Mips/MipsTargetObjectFile.cpp b/llvm/lib/Target/Mips/MipsTargetObjectFile.cpp
index f767c832198..f53ee0631b5 100644
--- a/llvm/lib/Target/Mips/MipsTargetObjectFile.cpp
+++ b/llvm/lib/Target/Mips/MipsTargetObjectFile.cpp
@@ -10,6 +10,7 @@
 #include "MipsTargetObjectFile.h"
 #include "MipsSubtarget.h"
 #include "MipsTargetMachine.h"
+#include "MCTargetDesc/MipsMCExpr.h"
 #include "llvm/BinaryFormat/ELF.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DerivedTypes.h"
@@ -189,6 +190,7 @@ const MCExpr *
 MipsTargetObjectFile::getDebugThreadLocalSymbol(const MCSymbol *Sym) const {
   const MCExpr *Expr =
       MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_None, getContext());
-  return MCBinaryExpr::createAdd(
+  Expr = MCBinaryExpr::createAdd(
       Expr, MCConstantExpr::create(0x8000, getContext()), getContext());
+  return MipsMCExpr::create(MipsMCExpr::MEK_DTPREL, Expr, getContext());
 }