Fix ARM EHABI handlerdata code generation.

[logan]

Summary

In r208166, several code has been added so that .eh_frame can
be generated for ARM in NetBSD, which is using Itanium C++ ABI
directly.

However, this will be incorrect when ARM EHABI is used.
With ARM EHABI, we should use DW_EH_PE_absptr for TTypeEncoding
instead.

[joerg]

See r208715. Feel free to add the test case.

[rengolin]

Hi Logan,

I've seen this error on libc++abi and on the test-suite (tramp3d-v4) when using libc++. LGTM.

Thanks,
--renato

[logan]

The test case has been committed in rL208790.

lib/MC/MCObjectFileInfo.cpp

default:
     break;
   }
 
   switch (T.getArch()) {
   case Triple::arm:
   case Triple::armeb:
   case Triple::thumb:
   case Triple::thumbeb:
+    // Most ARM ELF environment are using ARM EHABI, thus the default value
+    // dwarf::DW_EH_PE_absptr is correct.
+    if (T.getOS() == Triple::NetBSD) {
+      // For NetBSD ARM port, the Itanium C++ ABI adopted instead of EHABI.
+      PersonalityEncoding = (RelocM == Reloc::PIC_)
+        ? (dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
+           dwarf::DW_EH_PE_sdata4)
+        : dwarf::DW_EH_PE_absptr;
+      LSDAEncoding = (RelocM == Reloc::PIC_)
+        ? dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
+        : dwarf::DW_EH_PE_absptr;
+      TTypeEncoding = (RelocM == Reloc::PIC_)
+        ? (dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
+           dwarf::DW_EH_PE_sdata4)
+        : dwarf::DW_EH_PE_absptr;
+    }
+    break;
   case Triple::x86:
     PersonalityEncoding = (RelocM == Reloc::PIC_)
      ? dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
      : dwarf::DW_EH_PE_absptr;
     LSDAEncoding = (RelocM == Reloc::PIC_)
       ? dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
       : dwarf::DW_EH_PE_absptr;
     TTypeEncoding = (RelocM == Reloc::PIC_)

test/CodeGen/ARM/ehabi-handlerdata.ll

+; ARM EHABI test for the handlerdata.
+
+; This test case checks whether the handlerdata for exception
+; handling is generated properly.
+;
+; (1) The handlerdata must not be empty.
+; (2) LPStartEncoding == DW_EH_PE_omit
+; (3) TTypeEncoding == DW_EH_PE_absptr
+
+; RUN: llc -mtriple arm-unknown-linux-gnueabi -filetype=asm -o - %s \
+; RUN:   | FileCheck %s
+
+; RUN: llc -mtriple arm-unknown-linux-gnueabi -filetype=asm -o - %s \
+; RUN:     -relocation-model=pic \
+; RUN:   | FileCheck %s
+
+declare void @throw_exception()
+
+declare i32 @__gxx_personality_v0(...)
+
+declare i8* @__cxa_begin_catch(i8*)
+
+declare void @__cxa_end_catch()
+
+define void @test1() {
+entry:
+  invoke void @throw_exception() to label %try.cont unwind label %lpad
+
+lpad:
+  %0 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          catch i8* null
+  %1 = extractvalue { i8*, i32 } %0, 0
+  %2 = tail call i8* @__cxa_begin_catch(i8* %1)
+  tail call void @__cxa_end_catch()
+  br label %try.cont
+
+try.cont:
+  ret void
+}
+
+; CHECK:   .globl test1
+; CHECK:   .align 2
+; CHECK:   .type test1,%function
+; CHECK-LABEL: test1:
+; CHECK:   .fnstart
+; CHECK:   .personality __gxx_personality_v0
+; CHECK:   .handlerdata
+; CHECK:   .align 2
+; CHECK-LABEL: GCC_except_table0:
+; CHECK-LABEL: .Lexception0:
+; CHECK:   .byte 255                     @ @LPStart Encoding = omit
+; CHECK:   .byte 0                       @ @TType Encoding = absptr
+; CHECK:   .asciz
+; CHECK:   .byte 3                       @ Call site Encoding = udata4
+; CHECK:   .fnend