MIPS: Provide FPU info and decode FCSR in `info float'

This patch is the V2.  V1 can be found in
https://sourceware.org/ml/gdb-patches/2012-05/msg00938.html
V2 is to address Joel's comment
<https://sourceware.org/ml/gdb-patches/2012-06/msg00289.html> about
keeping dumping floating point registers.  Additionally, command
'info float' prints bits on nan2008 and abs2008.

------------------------------------------------------------------

 The change below provides a MIPS-specific handler for the:

(gdb) info float

command.  It provides information about the FPU type available (if any),
the FPU register width, and decodes the CP1 Floating Point Control and
Status Register (FCSR):

(gdb) print /x $fsr
$1 = 0xff83ffff
(gdb) info float
fpu type: double-precision
reg size: 32 bits
cond    : 0 1 2 3 4 5 6 7
cause   : inexact uflow oflow div0 inval unimp
mask    : inexact uflow oflow div0 inval
flags   : inexact uflow oflow div0 inval
rounding: -inf
flush   : zero

 One point to note about CP1.FCSR are the non-standard Flush-to-Nearest
and Flush-Override bits.  They are not a part of the MIPS architecture and
take two positions reserved for an implementation-dependent use in the
architecture.  They are present in all the FPU implementations made by
MIPS Technologies since the spin-off from SGI.

 I haven't been able to track down a single other MIPS FPU implementation
that would make any use of these bits and they are required to be
hardwired to zero by the architecture specification if unimplemented.
Therefore I think it makes sense to report them in the current way.

 GDB has no guaranteed access to the CP0 Processor Identification (PRId)
register to validate this feature properly and the ID information stored
in the CP1 Floating Point Implementation Register (FIR) is from my
experience not reliable enough (there's no Company ID available there for
once unlike in CP0.PRId and Processor ID is not guaranteed to be unique).

 As a side note we should probably dump CP1.FIR information as well, as
there's useful stuff indicating some FPU features there.  That's material
for another change however.

gdb/

2014-12-18  Nigel Stephens  <nigel@mips.com>
            Maciej W. Rozycki  <macro@codesourcery.com>

	* mips-tdep.c (print_fpu_flags): New function.
	(mips_print_float_info): Likewise.
	(mips_gdbarch_init): Install mips_print_float_info as gdbarch
	print_float_info routine.

gdb/testsuite/

2014-12-18  Nigel Stephens  <nigel@mips.com>
            Maciej W. Rozycki  <macro@codesourcery.com>

	* gdb.base/float.exp: Handle the new output from "info float" on
	MIPS targets.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 847944aad350cc1a0e4847f620187054021061ab..348a48fcc00efd49ade50c57164a18baf5036d50 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,11 @@
+2014-12-18  Nigel Stephens  <nigel@mips.com>
+           Maciej W. Rozycki  <macro@codesourcery.com>
+
+       * mips-tdep.c (print_fpu_flags): New function.
+       (mips_print_float_info): Likewise.
+       (mips_gdbarch_init): Install mips_print_float_info as gdbarch
+       print_float_info routine.
+
 2014-12-18  Yao Qi  <yao@codesourcery.com>
 
        * gdbarch.sh (print_float_info): Change its type from 'M' to 'm'.

diff --git a/gdb/mips-tdep.c b/gdb/mips-tdep.c
index eb99910c87097e3b1d340d3d779fe5e12c1207a9..60f43acbc2ac713b1fef6fa8ab37d05b6ca9f7bc 100644 (file)
--- a/gdb/mips-tdep.c
+++ b/gdb/mips-tdep.c
@@ -73,6 +73,9 @@ static int micromips_insn_at_pc_has_delay_slot (struct gdbarch *gdbarch,
 static int mips16_insn_at_pc_has_delay_slot (struct gdbarch *gdbarch,
                                             CORE_ADDR addr, int mustbe32);
 
+static void mips_print_float_info (struct gdbarch *, struct ui_file *,
+                                  struct frame_info *, const char *);
+
 /* A useful bit in the CP0 status register (MIPS_PS_REGNUM).  */
 /* This bit is set if we are emulating 32-bit FPRs on a 64-bit chip.  */
 #define ST0_FR (1 << 26)
@@ -6387,6 +6390,94 @@ mips_print_register (struct ui_file *file, struct frame_info *frame,
                              &opts, 0, file);
 }
 
+/* Print IEEE exception condition bits in FLAGS.  */
+
+static void
+print_fpu_flags (struct ui_file *file, int flags)
+{
+  if (flags & (1 << 0))
+    fputs_filtered (" inexact", file);
+  if (flags & (1 << 1))
+    fputs_filtered (" uflow", file);
+  if (flags & (1 << 2))
+    fputs_filtered (" oflow", file);
+  if (flags & (1 << 3))
+    fputs_filtered (" div0", file);
+  if (flags & (1 << 4))
+    fputs_filtered (" inval", file);
+  if (flags & (1 << 5))
+    fputs_filtered (" unimp", file);
+  fputc_filtered ('\n', file);
+}
+
+/* Print interesting information about the floating point processor
+   (if present) or emulator.  */
+
+static void
+mips_print_float_info (struct gdbarch *gdbarch, struct ui_file *file,
+                     struct frame_info *frame, const char *args)
+{
+  int fcsr = mips_regnum (gdbarch)->fp_control_status;
+  enum mips_fpu_type type = MIPS_FPU_TYPE (gdbarch);
+  ULONGEST fcs = 0;
+  int i;
+
+  if (fcsr == -1 || !read_frame_register_unsigned (frame, fcsr, &fcs))
+    type = MIPS_FPU_NONE;
+
+  fprintf_filtered (file, "fpu type: %s\n",
+                   type == MIPS_FPU_DOUBLE ? "double-precision"
+                   : type == MIPS_FPU_SINGLE ? "single-precision"
+                   : "none / unused");
+
+  if (type == MIPS_FPU_NONE)
+    return;
+
+  fprintf_filtered (file, "reg size: %d bits\n",
+                   register_size (gdbarch, mips_regnum (gdbarch)->fp0) * 8);
+
+  fputs_filtered ("cond    :", file);
+  if (fcs & (1 << 23))
+    fputs_filtered (" 0", file);
+  for (i = 1; i <= 7; i++)
+    if (fcs & (1 << (24 + i)))
+      fprintf_filtered (file, " %d", i);
+  fputc_filtered ('\n', file);
+
+  fputs_filtered ("cause   :", file);
+  print_fpu_flags (file, (fcs >> 12) & 0x3f);
+  fputs ("mask    :", stdout);
+  print_fpu_flags (file, (fcs >> 7) & 0x1f);
+  fputs ("flags   :", stdout);
+  print_fpu_flags (file, (fcs >> 2) & 0x1f);
+
+  fputs_filtered ("rounding: ", file);
+  switch (fcs & 3)
+    {
+    case 0: fputs_filtered ("nearest\n", file); break;
+    case 1: fputs_filtered ("zero\n", file); break;
+    case 2: fputs_filtered ("+inf\n", file); break;
+    case 3: fputs_filtered ("-inf\n", file); break;
+    }
+
+  fputs_filtered ("flush   :", file);
+  if (fcs & (1 << 21))
+    fputs_filtered (" nearest", file);
+  if (fcs & (1 << 22))
+    fputs_filtered (" override", file);
+  if (fcs & (1 << 24))
+    fputs_filtered (" zero", file);
+  if ((fcs & (0xb << 21)) == 0)
+    fputs_filtered (" no", file);
+  fputc_filtered ('\n', file);
+
+  fprintf_filtered (file, "nan2008 : %s\n", fcs & (1 << 18) ? "yes" : "no");
+  fprintf_filtered (file, "abs2008 : %s\n", fcs & (1 << 19) ? "yes" : "no");
+  fputc_filtered ('\n', file);
+
+  default_print_float_info (gdbarch, file, frame, args);
+}
+
 /* Replacement for generic do_registers_info.
    Print regs in pretty columns.  */
 
@@ -8737,6 +8828,8 @@ mips_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   set_gdbarch_push_dummy_code (gdbarch, mips_push_dummy_code);
   set_gdbarch_frame_align (gdbarch, mips_frame_align);
 
+  set_gdbarch_print_float_info (gdbarch, mips_print_float_info);
+
   set_gdbarch_convert_register_p (gdbarch, mips_convert_register_p);
   set_gdbarch_register_to_value (gdbarch, mips_register_to_value);
   set_gdbarch_value_to_register (gdbarch, mips_value_to_register);

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index f749d2e313658c7922caaf152b2a97c9bc62b2c7..518def127eff587b5c8e1fc19756f0e3bf4cb01b 100644 (file)
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2014-12-18  Nigel Stephens  <nigel@mips.com>
+           Maciej W. Rozycki  <macro@codesourcery.com>
+
+       * gdb.base/float.exp: Handle the new output from "info float" on
+       MIPS targets.
+
 2014-12-17  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
        Fix MinGW compilation.

diff --git a/gdb/testsuite/gdb.base/float.exp b/gdb/testsuite/gdb.base/float.exp
index 5da9630d2e430b66907f349dc16f7b5b57113d98..fbbd6826006350bf98a79dc4f71f7185b4fc8107 100644 (file)
--- a/gdb/testsuite/gdb.base/float.exp
+++ b/gdb/testsuite/gdb.base/float.exp
@@ -68,7 +68,14 @@ if { [istarget "aarch64*-*-*"] } then {
        }
     }
 } elseif [istarget "mips*-*-*"] then {
-    gdb_test "info float" "f0:.*flt:.*dbl:.*" "info float"
+    gdb_test_multiple "info float" "info float" {
+       -re "fpu type: none / unused\r\n$gdb_prompt $" {
+             pass "info float (without FPU)"
+         }
+       -re "fpu type:.*cause.*mask.*flags.*round.*flush.*f0:.*flt:.*dbl:.*$gdb_prompt $" {
+             pass "info float (with FPU)"
+         }
+    }
 } elseif [istarget "powerpc*-*-*"] then {
     gdb_test_multiple "info float" "info_float" {
         -re "f0.*f1.*f31.*fpscr.*$gdb_prompt $" {