x86: introduce .bfloat16 directive

This is to be able to generate data acted upon by AVX512-BF16 and
AMX-BF16 insns. While not part of the IEEE standard, the format is
sufficiently standardized to warrant handling in config/atof-ieee.c.
Arm, where custom handling was implemented, may want to leverage this as
well. To be able to also use the hex forms supported for other floating
point formats, a small addition to the generic hex_float() is needed.

Extend existing x86 testcases.

1 files changed, 2 insertions, 0 deletions

diff --git a/gas/read.c b/gas/read.c
index 4170a25..7333a2e 100644
--- a/gas/read.c
+++ b/gas/read.c
@@ -4852,6 +4852,8 @@ hex_float (int float_type, char *bytes)
 
   switch (float_type)
     {
+    case 'b':
+    case 'B':
     case 'h':
     case 'H':
       length = 2;