[mips] Fix FDE/CFI encoding in case of N32 ABI

[atanasyan]

Summary

For O32 and N32 ABI FDE/CFI encoding should be DW_EH_PE_sdata4 and only N64 ABI uses DW_EH_PE_sdata8. To cover all cases this patch check code pointer size and setup a correct FDE/CFI encoding type.

[smaksimovic]

LGTM

llvm/trunk/lib/MC/MCObjectFileInfo.cpp

void MCObjectFileInfo::initMachOMCObjectFileInfo(const Triple &T) {
 
   TLSExtraDataSection = TLSTLVSection;
 }
 
 void MCObjectFileInfo::initELFMCObjectFileInfo(const Triple &T, bool Large) {
   switch (T.getArch()) {
   case Triple::mips:
   case Triple::mipsel:
-    FDECFIEncoding = dwarf::DW_EH_PE_sdata4;
-    break;
   case Triple::mips64:
   case Triple::mips64el:
-    FDECFIEncoding = dwarf::DW_EH_PE_sdata8;
+    FDECFIEncoding = Ctx->getAsmInfo()->getCodePointerSize() == 4
+                         ? dwarf::DW_EH_PE_sdata4
+                         : dwarf::DW_EH_PE_sdata8;
     break;
   case Triple::ppc64:
   case Triple::ppc64le:
   case Triple::x86_64:
     FDECFIEncoding = dwarf::DW_EH_PE_pcrel |
                      (Large ? dwarf::DW_EH_PE_sdata8 : dwarf::DW_EH_PE_sdata4);
     break;
   case Triple::bpfel:

llvm/trunk/test/MC/Mips/cfi-encoding.s

+# RUN: llvm-mc -filetype=obj -triple mips--gnu -g %s \
+# RUN:   | llvm-objdump -s -section=.eh_frame - | FileCheck --check-prefix=O32 %s
+# RUN: llvm-mc -filetype=obj -triple mips64--gnuabin32 -g %s \
+# RUN:   | llvm-objdump -s -section=.eh_frame - | FileCheck --check-prefix=N32 %s
+# RUN: llvm-mc -filetype=obj -triple mips64--gnuabi64 -g %s \
+# RUN:   | llvm-objdump -s -section=.eh_frame - | FileCheck --check-prefix=N64 %s
+
+# O32: 0000 00000010 00000000 017a5200 017c1f01
+# O32: 0010 0b0c1d00 00000010 00000018 00000000
+# O32: 0020 00000004 00000000
+
+# N32: 0000 00000010 00000000 017a5200 017c1f01
+# N32: 0010 0b0c1d00 00000010 00000018 00000000
+# N32: 0020 00000004 00000000
+
+# N64: 0000 00000010 00000000 017a5200 01781f01
+# N64: 0010 0c0c1d00 00000018 00000018 00000000
+# N64: 0020 00000000 00000000 00000004 00000000
+
+foo:
+  .cfi_startproc
+  nop
+  .cfi_endproc