Add gdbarch callback to provide formats for debug info float types

At this point, all TYPE_CODE_FLT types carry their floating-point format,
except for those creating from reading DWARF or stabs debug info.  Those
will be addressed by this commit.

The main issue here is that we actually have to determine which floating-
point format to use.  Currently, we only have the type length as input
to this decision.  In the future, we may hopefully get --at least in
DWARF-- additional information to help disambiguate multiple different
formats of the same length.  For now, we can still look at the type name
as a hint.

This decision logic is encapsulated in a gdbarch callback to allow
platform-specific overrides.  The default implementation use the same
logic (compare type length against the various gdbarch_..._bit sizes)
that is currently implemented in floatformat_from_length.

With this commit, all platforms still use the default logic, so there
should be no actual change in behavior.  A follow-on commit will add
support for __float128 on Intel and Power.

Once dwarf2read.c and stabsread.c make use of the new callback to
determine floating-point formats, we're now sure every TYPE_CODE_FLT
type will always carry its format.  The commit therefore adds asserts
to verify_floatformat to ensure new code will continue to always
provide formats, and removes the code in floatformat_from_type that
used to handle types with a NULL TYPE_FLOATFORMAT.

gdb/ChangeLog:

	* gdbarch.sh (floatformat_for_type): New gdbarch callback.
	* gdbarch.h, gdbarch.c: Re-generate.
	* arch-utils.h (default_floatformat_for_type): New prototype.
	* arch-utils.c (default_floatformat_for_type): New function.

	* doublest.c (floatformat_from_length): Remove.
	(floatformat_from_type): Assume TYPE_FLOATFORMAT is non-NULL.
	* gdbtypes.c (verify_floatformat): Require non-NULL format.

	* dwarf2read.c (dwarf2_init_float_type): New function.
	(read_base_type): Use it.
	* stabsread.c (dbx_init_float_type): New function.
	(read_sun_floating_type): Use it.
	(read_range_type): Likewise.

Signed-off-by: Ulrich Weigand <ulrich.weigand@de.ibm.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/gdb/arch-utils.h b/gdb/arch-utils.h
index ad3f126..bbb0878 100644
--- a/gdb/arch-utils.h
+++ b/gdb/arch-utils.h
@@ -95,6 +95,11 @@ int cannot_register_not (struct gdbarch *gdbarch, int regnum);
 
 extern gdbarch_virtual_frame_pointer_ftype legacy_virtual_frame_pointer;
 
+/* Default implementation of gdbarch_floatformat_for_type.  */
+extern const struct floatformat **
+  default_floatformat_for_type (struct gdbarch *gdbarch,
+				const char *name, int len);
+
 extern CORE_ADDR generic_skip_trampoline_code (struct frame_info *frame,
 					       CORE_ADDR pc);