[PATCH] Fix Android MIPS exception personality encoding.

[Logan Chien]

The indirect pointer change should not limit to Android.

After checking the output of GCC on Debian mipsel port,
it seems that this change should be applied regardless the -fPIC
flags.

Besides, Joerg's comment is correct.  It seems that
MIPS doesn't allow PC-relative relocations between sections, thus
we should use DW_EH_PE_absptr instead of PW_EH_PE_pcrel.

p.s. DW_EH_PE_absptr = 0

http://reviews.llvm.org/D3828

Files:
  lib/CodeGen/AsmPrinter/DwarfCFIException.cpp
  lib/CodeGen/TargetLoweringObjectFileImpl.cpp
  lib/MC/MCObjectFileInfo.cpp
  test/CodeGen/Mips/ehframe-indirect.ll

Index: lib/CodeGen/AsmPrinter/DwarfCFIException.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfCFIException.cpp
+++ lib/CodeGen/AsmPrinter/DwarfCFIException.cpp
@@ -59,7 +59,8 @@
 
   unsigned PerEncoding = TLOF.getPersonalityEncoding();
 
-  if ((PerEncoding & 0x70) != dwarf::DW_EH_PE_pcrel)
+  if ((PerEncoding & 0x70) != dwarf::DW_EH_PE_pcrel &&
+      (PerEncoding & 0x80) != dwarf::DW_EH_PE_indirect)
     return;
 
   // Emit references to all used personality functions
Index: lib/CodeGen/TargetLoweringObjectFileImpl.cpp
===================================================================
--- lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -48,16 +48,13 @@
     const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
     MachineModuleInfo *MMI) const {
   unsigned Encoding = getPersonalityEncoding();
-  switch (Encoding & 0x70) {
-  default:
-    report_fatal_error("We do not support this DWARF encoding yet!");
-  case dwarf::DW_EH_PE_absptr:
-    return TM.getSymbol(GV, Mang);
-  case dwarf::DW_EH_PE_pcrel: {
+  if ((Encoding & 0x70) == dwarf::DW_EH_PE_pcrel ||
+      (Encoding & 0x80) == dwarf::DW_EH_PE_indirect)
     return getContext().GetOrCreateSymbol(StringRef("DW.ref.") +
                                           TM.getSymbol(GV, Mang)->getName());
-  }
-  }
+  if ((Encoding & 0x70) == dwarf::DW_EH_PE_absptr)
+    return TM.getSymbol(GV, Mang);
+  report_fatal_error("We do not support this DWARF encoding yet!");
 }
 
 void TargetLoweringObjectFileELF::emitPersonalityValue(MCStreamer &Streamer,
Index: lib/MC/MCObjectFileInfo.cpp
===================================================================
--- lib/MC/MCObjectFileInfo.cpp
+++ lib/MC/MCObjectFileInfo.cpp
@@ -319,6 +319,13 @@
       TTypeEncoding = dwarf::DW_EH_PE_absptr;
     }
     break;
+  case Triple::mips:
+  case Triple::mipsel:
+    // MIPS uses indirect pointer to refer personality functions, so that the
+    // eh_frame section can be read-only.  DW.ref.personality will be generated
+    // for relocation.
+    PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_absptr;
+    break;
   case Triple::ppc64:
   case Triple::ppc64le:
     PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
Index: test/CodeGen/Mips/ehframe-indirect.ll
===================================================================
--- /dev/null
+++ test/CodeGen/Mips/ehframe-indirect.ll
@@ -0,0 +1,34 @@
+; RUN: llc -mtriple=mipsel-linux-gnu < %s | FileCheck %s
+; RUN: llc -mtriple=mipsel-linux-android < %s | FileCheck %s
+
+define i32 @main() {
+; CHECK: .cfi_startproc
+; CHECK: .cfi_personality 128, DW.ref.__gxx_personality_v0
+
+entry:
+  invoke void @foo() to label %cont unwind label %lpad
+; CHECK: foo
+; CHECK: jalr
+
+lpad:
+  %0 = landingpad { i8*, i32 } personality i8*
+    bitcast (i32 (...)* @__gxx_personality_v0 to i8*) catch i8* null
+  ret i32 0
+
+cont:
+  ret i32 0
+}
+; CHECK: .cfi_endproc
+
+declare i32 @__gxx_personality_v0(...)
+
+declare void @foo()
+
+; CHECK: .hidden DW.ref.__gxx_personality_v0
+; CHECK: .weak DW.ref.__gxx_personality_v0
+; CHECK: .section .data.DW.ref.__gxx_personality_v0,"aGw", at progbits,DW.ref.__gxx_personality_v0,comdat
+; CHECK: .align 2
+; CHECK: .type DW.ref.__gxx_personality_v0, at object
+; CHECK: .size DW.ref.__gxx_personality_v0, 4
+; CHECK: DW.ref.__gxx_personality_v0:
+; CHECK: .4byte __gxx_personality_v0
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