Re: [PATCH] Proper _to_regnum for DWARF on Cygwin

[Brian Ford <ford@vss.fsi.com>]

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On Fri, 16 Apr 2004, Mark Kettenis wrote:

> On Tue, 13 Apr 2004, Brian Ford wrote:
>
>> 2004-04-13  Brian Ford  <ford@vss.fsi.com>
>>
>>	* i386-tdep.c (i386_coff_init_abi): New function.
>>	* i386-tdep.h (i386_coff_init_abi): New prototype.
>>	* i386-cygwin-tdep.c (i386_cygwin_init_abi): Call it.  Use correct
>>	register number translation functions for DWARF and DWARF 2.
>
> I've checked this one in now.

Thanks!

> Can you easily regenerate the rename patch now?  If so, feel free to
> mail it to me.  Otherwise I'll probably do it myself later this weekend.

Sure.

2004-04-16  Brian Ford  <ford@vss.fsi.com>

        * i386-tdep.c: Correct register numbering scheme comments throughout.
	(i386_stab_reg_to_regnum): Rename to i386_dbx_reg_to_regnum.
	(i386_dwarf_reg_to_regnum): Rename to i386_svr4_reg_to_regnum.
	(i386_coff_init_abi, i386_elf_init_abi): Accomodate renames above.
        (i386_gdb_arch_init): Likewise.

-- 
Brian Ford
Senior Realtime Software Engineer
VITAL - Visual Simulation Systems
FlightSafety International
Phone: 314-551-8460
Fax:   314-551-8444

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Index: i386-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/i386-tdep.c,v
retrieving revision 1.186
diff -u -p -r1.186 i386-tdep.c
--- i386-tdep.c	16 Apr 2004 16:49:55 -0000	1.186
+++ i386-tdep.c	16 Apr 2004 17:21:59 -0000
@@ -51,8 +51,7 @@
 #include "i386-tdep.h"
 #include "i387-tdep.h"
 
-/* Names of the registers.  The first 10 registers match the register
-   numbering scheme used by GCC for stabs and DWARF.  */
+/* Register names by GDB cooked register number.  */
 
 static char *i386_register_names[] =
 {
@@ -166,49 +165,13 @@ i386_register_name (int reg)
   return NULL;
 }
 
-
-/* FIXME: jimb/2004-04-01: I don't think these functions are right.
-   For a given platform, GCC always uses the same register numbering
-   in both STABS and Dwarf2: gcc/dbxout.c and gcc/dwarf2out.c both use
-   the DBX_REGISTER_NUMBER macro, as defined by the config headers.
-   If you compile a program so that its variables are allocated to
-   floating-point registers, first with STABS and again with Dwarf 2,
-   you'll see that the variable's register numbers are the same in
-   each case.
-
-   GCC does use (at least) two different register numberings on the
-   i386; they differ in how they number %ebp, %esp, %eflags, and the
-   floating-point registers.  And it has a third numbering for "64bit
-   mode", which I assume is x86_64.  But it always uses a given
-   numbering in both STABS and Dwarf.
-
-   This does not match the arrangement we have below, which presumes
-   that STABS and Dwarf numberings are different, and does some
-   strange mixing and matching (e.g., registering the Dwarf 2 function
-   as the STABS function for "Generic i386 ELF") to get close enough
-   to the right effect on the platforms we care about.
-
-   If we wanted to match GCC, we should have two separate register
-   number translation functions (we handle x86_64 in a separate tdep
-   file altogether), one corresponding to each of GCC's i386 register
-   maps.  And for a given platform, we would register one of them as
-   both the STABS and Dwarf 2 functions.
-
-   However, we don't aspire to match GCC; we aspire to match the
-   native system's tools.  I don't have access to lots of different
-   native compilers and debuggers to verify that GCC is matching their
-   behavior in this regard.  Is it sufficient to argue that we at
-   least want to match GNU's compiler, and say we'll fix bugs relative
-   to native tools as they're reported?  */
-
-
-/* Convert stabs register number REG to the appropriate register
-   number used by GDB.  */
+/* Convert a dbx style register number to the appropriate
+   GDB cooked register number.  */
 
 static int
-i386_stab_reg_to_regnum (int reg)
+i386_dbx_reg_to_regnum (int reg)
 {
-  /* This implements what GCC calls the "default" register map.  */
+  /* This translates what GCC calls the dbx_register_map[].  */
   if (reg >= 0 && reg <= 7)
     {
       /* General-purpose registers.  The debug info calls %ebp
@@ -239,14 +202,15 @@ i386_stab_reg_to_regnum (int reg)
   return NUM_REGS + NUM_PSEUDO_REGS;
 }
 
-/* Convert DWARF register number REG to the appropriate register
-   number used by GDB.  */
+/* Convert a SVR4 style register number to the appropriate
+   GDB cooked register number.  */
 
 static int
-i386_dwarf_reg_to_regnum (int reg)
+i386_svr4_reg_to_regnum (int reg)
 {
-  /* The DWARF register numbering includes %eip and %eflags, and
-     numbers the floating point registers differently.  */
+  /* This translates what GCC calls the svr4_dbx_register_map[].
+     It includes %eip and %eflags, and numbers the floating-point
+     registers differently.  */
   if (reg >= 0 && reg <= 9)
     {
       /* General-purpose registers.  */
@@ -259,8 +223,8 @@ i386_dwarf_reg_to_regnum (int reg)
     }
   else if (reg >= 21)
     {
-      /* The SSE and MMX registers have identical numbers as in stabs.  */
-      return i386_stab_reg_to_regnum (reg);
+      /* SSE and MMX registers have identical numbers in the dbx style map.  */
+      return i386_dbx_reg_to_regnum (reg);
     }
 
   /* This will hopefully provoke a warning.  */
@@ -1819,9 +1783,9 @@ i386_svr4_sigcontext_addr (struct frame_
 void
 i386_coff_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 {
-  /* We typically use DWARF-in-COFF with the stabs register numbering.  */
-  set_gdbarch_dwarf_reg_to_regnum (gdbarch, i386_stab_reg_to_regnum);
-  set_gdbarch_dwarf2_reg_to_regnum (gdbarch, i386_stab_reg_to_regnum);
+  /* We typically use DWARF-in-COFF with the dbx style register numbering.  */
+  set_gdbarch_dwarf_reg_to_regnum (gdbarch, i386_dbx_reg_to_regnum);
+  set_gdbarch_dwarf2_reg_to_regnum (gdbarch, i386_dbx_reg_to_regnum);
 }
 
 /* Generic ELF.  */
@@ -1829,8 +1793,8 @@ i386_coff_init_abi (struct gdbarch_info 
 void
 i386_elf_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 {
-  /* We typically use stabs-in-ELF with the DWARF register numbering.  */
-  set_gdbarch_stab_reg_to_regnum (gdbarch, i386_dwarf_reg_to_regnum);
+  /* We typically use stabs-in-ELF with the SVR4 style register numbering.  */
+  set_gdbarch_stab_reg_to_regnum (gdbarch, i386_svr4_reg_to_regnum);
 }
 
 /* System V Release 4 (SVR4).  */
@@ -2024,13 +1988,40 @@ i386_gdbarch_init (struct gdbarch_info i
   set_gdbarch_ps_regnum (gdbarch, I386_EFLAGS_REGNUM); /* %eflags */
   set_gdbarch_fp0_regnum (gdbarch, I386_ST0_REGNUM); /* %st(0) */
 
-  /* Use the "default" register numbering scheme for stabs and COFF.  */
-  set_gdbarch_stab_reg_to_regnum (gdbarch, i386_stab_reg_to_regnum);
-  set_gdbarch_sdb_reg_to_regnum (gdbarch, i386_stab_reg_to_regnum);
-
-  /* Use the DWARF register numbering scheme for DWARF and DWARF 2.  */
-  set_gdbarch_dwarf_reg_to_regnum (gdbarch, i386_dwarf_reg_to_regnum);
-  set_gdbarch_dwarf2_reg_to_regnum (gdbarch, i386_dwarf_reg_to_regnum);
+/* FIXME: ford/2004-04-09: Currently, each GCC i386 target uses the
+   same register numbering scheme across all of its supported debugging
+   formats ie. sdb (COFF), stabs, and DWARF 2.  gcc/ sdbout.c, dbxout.c,
+   and dwarf2out.c all use the DBX_REGISTER_NUMBER macro, which is defined
+   by each target's respective config header in a manner independant of
+   the requested output debugging format.
+
+   GCC does have two possible register numbering schemes on the i386:
+   dbx and SVR4.  These schemes differ in how they number %ebp, %esp,
+   %eflags, and the floating-point registers.  GCC also has a third
+   possible numbering scheme used exclusively in "64bit mode": dbx64,
+   which I assume corresponds to x86_64, for which we have a seperate
+   -tdep file.
+
+   This does not match the arrangement below, which presumes that the
+   sdb and stabs numbering schemes differ from the DWARF and DWARF 2
+   ones.  i386_[coff|elf]_init_abi exists only to correct this presumption.
+   If we wanted to match GCC, then for any given target, we would only
+   use one register number translation function across all its supported
+   debug formats.  However, we don't aspire to match GCC, we aspire to
+   match the native system's tools.  But, I don't have access to lots of
+   different native compilers and debuggers in order to verify that GCC
+   is matching their behavior in this regard.
+
+   Is it sufficient to argue that we at least want to match GNU's compiler,
+   and we'll fix bugs relative to the native tools as they're reported?  */
+
+  /* Use the dbx style register numbering scheme for stabs and sdb (COFF).  */
+  set_gdbarch_stab_reg_to_regnum (gdbarch, i386_dbx_reg_to_regnum);
+  set_gdbarch_sdb_reg_to_regnum (gdbarch, i386_dbx_reg_to_regnum);
+
+  /* Use the SVR4 style register numbering scheme for DWARF and DWARF 2.  */
+  set_gdbarch_dwarf_reg_to_regnum (gdbarch, i386_svr4_reg_to_regnum);
+  set_gdbarch_dwarf2_reg_to_regnum (gdbarch, i386_svr4_reg_to_regnum);
 
   /* We don't define ECOFF_REG_TO_REGNUM, since ECOFF doesn't seem to
      be in use on any of the supported i386 targets.  */