Handle half-float in 'x' command

Using 'x/hf' should print bytes as float16, but instead it currently
prints as an integer.  I tracked this down to a missing case in
float_type_from_length.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30161
Approved-By: Simon Marchi <simon.marchi@efficios.com>

3 files changed, 51 insertions, 2 deletions

diff --git a/gdb/printcmd.c b/gdb/printcmd.c
index 341efc7..ae59a14 100644
--- a/gdb/printcmd.c
+++ b/gdb/printcmd.c
@@ -349,7 +349,9 @@ float_type_from_length (struct type *type)
   struct gdbarch *gdbarch = type->arch ();
   const struct builtin_type *builtin = builtin_type (gdbarch);
 
-  if (type->length () == builtin->builtin_float->length ())
+  if (type->length () == builtin->builtin_half->length ())
+    type = builtin->builtin_half;
+  else if (type->length () == builtin->builtin_float->length ())
     type = builtin->builtin_float;
   else if (type->length () == builtin->builtin_double->length ())
     type = builtin->builtin_double;
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-bfloat16.c b/gdb/testsuite/gdb.dwarf2/dw2-bfloat16.c
new file mode 100644
index 0000000..30dcd38
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-bfloat16.c
@@ -0,0 +1,26 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2023 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/>.  */
+
+/* Storage for the 'x' test.  */
+unsigned char storage[2];
+
+int
+main()
+{
+  asm ("main_label: .globl main_label");
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-bfloat16.exp b/gdb/testsuite/gdb.dwarf2/dw2-bfloat16.exp
index 79058ca..f832e14 100644
--- a/gdb/testsuite/gdb.dwarf2/dw2-bfloat16.exp
+++ b/gdb/testsuite/gdb.dwarf2/dw2-bfloat16.exp
@@ -21,7 +21,7 @@ load_lib dwarf.exp
 # This test can only be run on targets which support DWARF-2 and use gas.
 require dwarf2_support
 
-standard_testfile main.c -dw.S
+standard_testfile .c -dw.S
 
 # Make some DWARF for the test.
 # 0x4049 is the equivalent of 3.141 for bfloat16.
@@ -78,3 +78,24 @@ if ![runto_main] {
 # Make sure we can print both types correctly.
 gdb_test "print bf16_1" " = 3.141"
 gdb_test "print fp16_1" " = 3.1406"
+
+#
+# Test that 'x/hf' correctly handles "half float".
+#
+
+set bytes {0x48 0x42}
+set endian [get_endianness]
+if {$endian == "big"} {
+    set bytes [lreverse $bytes]
+}
+
+gdb_test_no_output "set var \$s = (unsigned char *) &storage" \
+    "set convenience variable"
+gdb_test "print/x \$s\[0\] = [lindex $bytes 0]" \
+    " = $hex" "set first element"
+gdb_test "print/x \$s\[1\] = [lindex $bytes 1]" \
+    " = $hex" "set second element"
+gdb_test "print *(__fp16 *) \$s" " = 3\\.1406" \
+    "print float16 value"
+gdb_test "x/hf \$s" "$hex <storage>:\[ \t\]*3\\.1406" \
+    "examine float16 value"