RS6000 Add support to print vector register contents as float128

This patch adds a floating point 128-bit composite field to the vsx
register type.  When printing the register with p/f the float128 field will
be printed as a 128-bit floating point value.  A test case to verify the new
vsx register field is visible and correctly prints out the value of a 128-bit
floating point value is also added.

gdb/ChangeLog:

	* rs6000-tdep.c (rs6000_builtin_type_vec128): Add t_float128 variable.
	(rs6000_builtin_type_vec128): Add append_composite_type_field for
	float128.

gdb/testsuite/ChangeLog:

	* gdb.arch/vsx-vsr-float128.c: New test file.
	* gdb.arch/vsx-vsr-float128.exp: New expect file.

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2021-4-12  Carl Love  <cel@us.ibm.com>
+
+	* rs6000-tdep.c (rs6000_builtin_type_vec128): Add t_float128 variable.
+	(rs6000_builtin_type_vec128): Add append_composite_type_field for
+	float128.
+
 2021-04-12  Simon Marchi  <simon.marchi@polymtl.ca>
 
 	* nat/windows-nat.c: Remove all code guarded by _WIN32_WCE.

gdb/rs6000-tdep.c

@@ -2355,6 +2355,7 @@ rs6000_builtin_type_vec128 (struct gdbarch *gdbarch)
       /* The type we're building is this
 
 	 type = union __ppc_builtin_type_vec128 {
+	     float128_t float128;
 	     uint128_t uint128;
 	     double v2_double[2];
 	     float v4_float[4];
@@ -2364,10 +2365,15 @@ rs6000_builtin_type_vec128 (struct gdbarch *gdbarch)
 	 }
       */
 
+      /* PPC specific type for IEEE 128-bit float field */
+      struct type *t_float128
+	= arch_float_type (gdbarch, 128, "float128_t", floatformats_ia64_quad);
+
       struct type *t;
 
       t = arch_composite_type (gdbarch,
 			       "__ppc_builtin_type_vec128", TYPE_CODE_UNION);
+      append_composite_type_field (t, "float128", t_float128);
       append_composite_type_field (t, "uint128", bt->builtin_uint128);
       append_composite_type_field (t, "v2_double",
 				   init_vector_type (bt->builtin_double, 2));

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2021-4-12  Carl Love  <cel@us.ibm.com>
+
+	* gdb.arch/vsx-vsr-float128.c: New test file.
+	* gdb.arch/vsx-vsr-float128.exp: New expect file.
+
 2021-04-12  Markus Metzger  <markus.t.metzger@intel.com>
 
 	* gdb.btrace/reconnect.exp: Relax expected stepi output.

gdb/testsuite/gdb.arch/vsx-vsr-float28.c

@@ -0,0 +1,31 @@
+/* This file is part of GDB, the GNU debugger.
+
+   Copyright 2008-2021 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <altivec.h>
+#include <stdio.h>
+
+int
+main ()
+{
+  __float128 x, y, z;
+
+  x = -2.25;
+  y = 3.5;
+  z = x * y;
+
+  return 0;
+}

gdb/testsuite/gdb.arch/vsx-vsr-float28.exp

@@ -0,0 +1,90 @@
+# Copyright (C) 2008-2021 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+#
+# Test the vsr registers print values in float128 bit format.
+#
+
+
+if {![istarget "powerpc*"] || [skip_vsx_tests]} then {
+    verbose "Skipping vsr float128 field tests."
+    return
+}
+
+standard_testfile
+
+set compile_flags {debug nowarnings quiet}
+if [get_compiler_info] {
+    warning "get_compiler failed"
+    return -1
+}
+
+if [test_compiler_info gcc*] {
+    set compile_flags "$compile_flags additional_flags=-maltivec additional_flags=-mabi=altivec"
+} elseif [test_compiler_info xlc*] {
+    set compile_flags "$compile_flags additional_flags=-qaltivec"
+} else {
+    warning "unknown compiler"
+    return -1
+}
+
+if  { [gdb_compile ${srcdir}/${subdir}/${srcfile} ${binfile} executable $compile_flags] != "" } {
+     untested "failed to compile"
+     return -1
+}
+
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
+# Run to `main' where we begin our tests.
+
+if ![runto_main] then {
+    fail "can't run to main"
+    return 0
+}
+
+set endianness [get_endianness]
+
+# Data sets used throughout the test
+
+set vector_field ".*float128 = -2.25,.*"
+
+# The vsx registers now contain a 128-bit floating point field.  The following tests
+# setting a vsr register with a 128-bit floating point value and then printing the
+# register contents using the float format to verify the value is correctly printed
+# as a 128-bit value.
+
+# the following corresponds to a 128-bit float value of -2.25
+if {$endianness == "big"} {
+    gdb_test_no_output "set \$vs1.v4_int32\[3\] = 0x0"
+    gdb_test_no_output "set \$vs1.v4_int32\[2\] = 0x0"
+    gdb_test_no_output "set \$vs1.v4_int32\[1\] = 0x0"
+    gdb_test_no_output "set \$vs1.v4_int32\[0\] = 0xc0002000"
+} else {
+    gdb_test_no_output "set \$vs1.v4_int32\[0\] = 0x0"
+    gdb_test_no_output "set \$vs1.v4_int32\[1\] = 0x0"
+    gdb_test_no_output "set \$vs1.v4_int32\[2\] = 0x0"
+    gdb_test_no_output "set \$vs1.v4_int32\[3\] = 0xc0002000"
+}
+
+# check the contents of the register
+gdb_test "p/f \$vs1" "$vector_field"
+
+gdb_exit
+
+
+