Imported gcc-4.4.3

[msp430-gcc.git] / gcc / config / m32c / m32c.abi

diff --git a/gcc/config/m32c/m32c.abi b/gcc/config/m32c/m32c.abi
new file mode 100644 (file)
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+++ b/gcc/config/m32c/m32c.abi
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+   Target Definitions for R8C/M16C/M32C
+   Copyright (C) 2005, 2007
+   Free Software Foundation, Inc.
+   Contributed by Red Hat.
+
+   This file is part of GCC.
+
+   GCC 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, or (at your
+   option) any later version.
+
+   GCC 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 GCC; see the file COPYING3.  If not see
+   <http://www.gnu.org/licenses/>.
+
+
+These are just some random notes I used during development of this
+port.  Please don't consider these to be "official" specifications,
+just additional information to help make the code easier to
+understand.
+
+
+Frame
+=====
+
+       +--------------------
+       | incoming args
+       +--------------------
+       | return Address
+osp -> +--------------------
+       | saved fp
+fp ->  +--------------------
+       | local data
+       +--------------------
+       | saved regs
+       +--------------------
+       | outgoing args (opt)
+sp ->  +--------------------
+
+Argument Passing
+================
+
+r8c, m16c
+---------
+
+First arg may be passed in r1l or r1 if it (1) fits (QImode or
+HImode), (2) is named, and (3) is an integer or pointer type (no
+structs, floats, etc).  Otherwise, it's passed on the stack.
+
+Second arg may be passed in r2, same restrictions (but not QImode),
+even if the first arg is passed on the stack.
+
+Third and further args are passed on the stack.  No padding is used,
+stack "alignment" is 8 bits.
+
+m32cm, m32c
+-----------
+First arg may be passed in r0l or r0, same restrictions as above.
+
+Second and further args are passed on the stack.  Padding is used
+after QImode parameters (i.e. lower-addressed byte is the value,
+higher-addressed byte is the padding), stack "alignment" is 16 bits.
+
+
+Return Value
+============
+
+r8c, m16c
+---------
+
+QImode in r0l
+HImode in r0
+near pointer in r0
+(desired)
+SImode in r2r0
+far pointer in r2r0
+(actual)
+Anything bigger than 16 bits is returned in memory, at mem0 (mem0
+through mem15 are provided by libgcc.a)
+
+Aggregate values (regardless of size) are returned by pushing a
+pointer to a temporary area on the stack after the args are pushed.
+The function fills in this area with the value.  Note that this
+pointer on the stack does not affect how register arguments, if any,
+are configured.
+
+m32cm, m32c
+-----------
+Same.
+
+
+Registers Preserved Across Calls
+================================
+
+r8c, m16c
+---------
+sb, fb, sp (i.e. nearly all registers are call clobbered)
+
+m32cm, m32c
+-----------
+r1, r2, r3, a0, a1, sb, fb, sp
+(except when used for return values)
+
+
+Interrupt Handlers
+==================
+
+The stack frame is slightly different for interrupt handlers, because
+(1) we don't have a usable parent frame, and (2) we have to use
+special instructions to return and thus must save/restore everything
+differently.
+
+       +--------------------
+       | program state
+osp -> +--------------------
+       | return address
+       +--------------------
+       | saved r0..fp (pushm)
+fp ->  +--------------------
+       | local data
+       +--------------------
+       | saved regs mem0..mem15
+       +--------------------
+       | outgoing args (opt)
+sp ->  +--------------------
+