gas: Add --gdwarf-cie-version command line flag

Add a flag to control the version of CIE that is generated.  By
default gas produces CIE version 1, and this continues to be the
default after this patch.

However, a user can now provide --gdwarf-cie-version=NUMBER to switch
to either version 3 or version 4 of CIE, version 2 was never released,
and so causes an error as does any number less than 1 or greater than
4.

Producing version 4 CIE requires two new fields to be added to the
CIE, an address size field, and an segment selector field.  For a flat
address space the DWARF specification indicates that the segment
selector should be 0, and the address size fields just contains the
address size in bytes.  For now we support 4 or 8 byte addresses, and
the segment selector is always produced as 0.  At some future time we
might need to allow targets to override this.

gas/ChangeLog:

	* as.c (parse_args): Parse --gdwarf-cie-version option.
	(flag_dwarf_cie_version): New variable.
	* as.h (flag_dwarf_cie_version): Declare.
	* dw2gencfi.c (output_cie): Switch from DW_CIE_VERSION to
	flag_dwarf_cie_version.
	* doc/as.texi (Overview): Document --gdwarf-cie-version.
	* NEWS: Likewise.
	* testsuite/gas/cfi/cfi.exp: Add new tests.
	* testsuite/gas/cfi/cie-version-0.d: New file.
	* testsuite/gas/cfi/cie-version-1.d: New file.
	* testsuite/gas/cfi/cie-version-2.d: New file.
	* testsuite/gas/cfi/cie-version-3.d: New file.
	* testsuite/gas/cfi/cie-version-4.d: New file.
	* testsuite/gas/cfi/cie-version.s: New file.

include/ChangeLog:

	* dwarf2.h (DW_CIE_VERSION): Delete.

Change-Id: I9de19461aeb8332b5a57bbfe802953d0725a7ae8

1 files changed, 17 insertions, 0 deletions

diff --git a/gas/as.c b/gas/as.c
index d53db11..cc84725 100644
--- a/gas/as.c
+++ b/gas/as.c
@@ -95,6 +95,11 @@ int debug_memory = 0;
 /* Enable verbose mode.  */
 int verbose = 0;
 
+/* Which version of DWARF CIE to produce.  The default could be overridden
+   by a target during its initialisation, or by the --gdwarf-cie-version
+   command line flag.  */
+int flag_dwarf_cie_version = 1;
+
 #if defined OBJ_ELF || defined OBJ_MAYBE_ELF
 int flag_use_elf_stt_common = DEFAULT_GENERATE_ELF_STT_COMMON;
 bfd_boolean flag_generate_build_notes = DEFAULT_GENERATE_BUILD_NOTES;
@@ -479,6 +484,7 @@ parse_args (int * pargc, char *** pargv)
       OPTION_GSTABS_PLUS,
       OPTION_GDWARF2,
       OPTION_GDWARF_SECTIONS,
+      OPTION_GDWARF_CIE_VERSION,
       OPTION_STRIP_LOCAL_ABSOLUTE,
       OPTION_TRADITIONAL_FORMAT,
       OPTION_WARN,
@@ -534,6 +540,7 @@ parse_args (int * pargc, char *** pargv)
        so we keep it here for backwards compatibility.  */
     ,{"gdwarf2", no_argument, NULL, OPTION_GDWARF2}
     ,{"gdwarf-sections", no_argument, NULL, OPTION_GDWARF_SECTIONS}
+    ,{"gdwarf-cie-version", required_argument, NULL, OPTION_GDWARF_CIE_VERSION}
     ,{"gen-debug", no_argument, NULL, 'g'}
     ,{"gstabs", no_argument, NULL, OPTION_GSTABS}
     ,{"gstabs+", no_argument, NULL, OPTION_GSTABS_PLUS}
@@ -828,6 +835,16 @@ This program has absolutely no warranty.\n"));
 	  flag_dwarf_sections = TRUE;
 	  break;
 
+        case OPTION_GDWARF_CIE_VERSION:
+	  flag_dwarf_cie_version = atoi (optarg);
+          /* The available CIE versions are 1 (DWARF 2), 3 (DWARF 3), and 4
+             (DWARF 4 and 5).  */
+	  if (flag_dwarf_cie_version < 1
+              || flag_dwarf_cie_version == 2
+              || flag_dwarf_cie_version > 4)
+            as_fatal (_("Invalid --gdwarf-cie-version `%s'"), optarg);
+	  break;
+
 	case 'J':
 	  flag_signed_overflow_ok = 1;
 	  break;