From 9fb4dd364d203daeb606490e1cb27b8ee796e8c3 Mon Sep 17 00:00:00 2001 From: Jim Blandy Date: Sat, 8 Apr 2000 17:49:31 +0000 Subject: [PATCH] * gdbint.texinfo (Using Different Register and Memory Data Representations): New section. (REGISTER_CONVERTIBLE, REGISTER_RAW_SIZE, REGISTER_VIRTUAL_SIZE, REGISTER_VIRTUAL_TYPE, REGISTER_CONVERT_TO_VIRTUAL, REGISTER_CONVERT_TO_RAW): Document. --- gdb/doc/gdbint.texinfo | 115 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 115 insertions(+) diff --git a/gdb/doc/gdbint.texinfo b/gdb/doc/gdbint.texinfo index b104060..25b116e 100644 --- a/gdb/doc/gdbint.texinfo +++ b/gdb/doc/gdbint.texinfo @@ -1153,6 +1153,97 @@ in the @code{REGISTER_NAME} and related macros. GDB can handle big-endian, little-endian, and bi-endian architectures. +@section Using Different Register and Memory Data Representations +@cindex raw representation +@cindex virtual representation +@cindex representations, raw and virtual +@cindex register data formats, converting +@cindex @code{struct value}, converting register contents to + +Some architectures use one representation for a value when it lives in a +register, but use a different representation when it lives in memory. +In GDB's terminology, the @dfn{raw} representation is the one used in +the target registers, and the @dfn{virtual} representation is the one +used in memory, and within GDB @code{struct value} objects. + +For almost all data types on almost all architectures, the virtual and +raw representations are identical, and no special handling is needed. +However, they do occasionally differ. For example: + +@itemize @bullet + +@item +The x86 architecture supports an 80-bit long double type. However, when +we store those values in memory, they occupy twelve bytes: the +floating-point number occupies the first ten, and the final two bytes +are unused. This keeps the values aligned on four-byte boundaries, +allowing more efficient access. Thus, the x86 80-bit floating-point +type is the raw representation, and the twelve-byte loosely-packed +arrangement is the virtual representation. + +@item +Some 64-bit MIPS targets present 32-bit registers to GDB as 64-bit +registers, with garbage in their upper bits. GDB ignores the top 32 +bits. Thus, the 64-bit form, with garbage in the upper 32 bits, is the +raw representation, and the trimmed 32-bit representation is the +virtual representation. + +@end itemize + +In general, the raw representation is determined by the architecture, or +GDB's interface to the architecture, while the virtual representation +can be chosen for GDB's convenience. GDB's register file, +@code{registers}, holds the register contents in raw format, and the GDB +remote protocol transmits register values in raw format. + +Your architecture may define the following macros to request raw / +virtual conversions: + +@deftypefn {Target Macro} int REGISTER_CONVERTIBLE (int @var{reg}) +Return non-zero if register number @var{reg}'s value needs different raw +and virtual formats. +@end deftypefn + +@deftypefn {Target Macro} int REGISTER_RAW_SIZE (int @var{reg}) +The size of register number @var{reg}'s raw value. This is the number +of bytes the register will occupy in @code{registers}, or in a GDB +remote protocol packet. +@end deftypefn + +@deftypefn {Target Macro} int REGISTER_VIRTUAL_SIZE (int @var{reg}) +The size of register number @var{reg}'s value, in its virtual format. +This is the size a @code{struct value}'s buffer will have, holding that +register's value. +@end deftypefn + +@deftypefn {Target Macro} struct type *REGISTER_VIRTUAL_TYPE (int @var{reg}) +This is the type of the virtual representation of register number +@var{reg}. Note that there is no need for a macro giving a type for the +register's raw form; once the register's value has been obtained, GDB +always uses the virtual form. +@end deftypefn + +@deftypefn {Target Macro} void REGISTER_CONVERT_TO_VIRTUAL (int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to}) +Convert the value of register number @var{reg} to @var{type}, which +should always be @code{REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer +at @var{from} holds the register's value in raw format; the macro should +convert the value to virtual format, and place it at @var{to}. + +Note that REGISTER_CONVERT_TO_VIRTUAL and REGISTER_CONVERT_TO_RAW take +their @var{reg} and @var{type} arguments in different orders. +@end deftypefn + +@deftypefn {Target Macro} void REGISTER_CONVERT_TO_RAW (struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to}) +Convert the value of register number @var{reg} to @var{type}, which +should always be @code{REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer +at @var{from} holds the register's value in raw format; the macro should +convert the value to virtual format, and place it at @var{to}. + +Note that REGISTER_CONVERT_TO_VIRTUAL and REGISTER_CONVERT_TO_RAW take +their @var{reg} and @var{type} arguments in different orders. +@end deftypefn + + @section Frame Interpretation @section Inferior Call Setup @@ -1584,6 +1675,30 @@ text section. (Seems dubious.) @item NO_HIF_SUPPORT (Specific to the a29k.) +@item REGISTER_CONVERTIBLE (@var{reg}) +Return non-zero if @var{reg} uses different raw and virtual formats. +@xref{Using Different Target and Host Data Representations}. + +@item REGISTER_RAW_SIZE (@var{reg}) +Return the raw size of @var{reg}. +@xref{Using Different Target and Host Data Representations}. + +@item REGISTER_VIRTUAL_SIZE (@var{reg}) +Return the virtual size of @var{reg}. +@xref{Using Different Target and Host Data Representations}. + +@item REGISTER_VIRTUAL_TYPE (@var{reg}) +Return the virtual type of @var{reg}. +@xref{Using Different Target and Host Data Representations}. + +@item REGISTER_CONVERT_TO_VIRTUAL(@var{reg}, @var{type}, @var{from}, @var{to}) +Convert the value of register @var{reg} from its raw form to its virtual +form. @xref{Using Different Target and Host Data Representations}. + +@item REGISTER_CONVERT_TO_RAW(@var{type}, @var{reg}, @var{from}, @var{to}) +Convert the value of register @var{reg} from its virtual form to its raw +form. @xref{Using Different Target and Host Data Representations}. + @item SOFTWARE_SINGLE_STEP_P Define this as 1 if the target does not have a hardware single-step mechanism. The macro @code{SOFTWARE_SINGLE_STEP} must also be defined. -- 2.7.4