| Target Definitions for R8C/M16C/M32C |
| Copyright (C) 2005-2015 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 -> +-------------------- |
| |