m32c.abi revision 1.1.1.1.4.2
1 Target Definitions for R8C/M16C/M32C 2 Copyright (C) 2005, 2007 3 Free Software Foundation, Inc. 4 Contributed by Red Hat. 5 6 This file is part of GCC. 7 8 GCC is free software; you can redistribute it and/or modify it 9 under the terms of the GNU General Public License as published 10 by the Free Software Foundation; either version 3, or (at your 11 option) any later version. 12 13 GCC is distributed in the hope that it will be useful, but WITHOUT 14 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 15 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public 16 License for more details. 17 18 You should have received a copy of the GNU General Public License 19 along with GCC; see the file COPYING3. If not see 20 <http://www.gnu.org/licenses/>. 21 22 23 These are just some random notes I used during development of this 24 port. Please don't consider these to be "official" specifications, 25 just additional information to help make the code easier to 26 understand. 27 28 29 Frame 30 ===== 31 32 +-------------------- 33 | incoming args 34 +-------------------- 35 | return Address 36 osp -> +-------------------- 37 | saved fp 38 fp -> +-------------------- 39 | local data 40 +-------------------- 41 | saved regs 42 +-------------------- 43 | outgoing args (opt) 44 sp -> +-------------------- 45 46 Argument Passing 47 ================ 48 49 r8c, m16c 50 --------- 51 52 First arg may be passed in r1l or r1 if it (1) fits (QImode or 53 HImode), (2) is named, and (3) is an integer or pointer type (no 54 structs, floats, etc). Otherwise, it's passed on the stack. 55 56 Second arg may be passed in r2, same restrictions (but not QImode), 57 even if the first arg is passed on the stack. 58 59 Third and further args are passed on the stack. No padding is used, 60 stack "alignment" is 8 bits. 61 62 m32cm, m32c 63 ----------- 64 First arg may be passed in r0l or r0, same restrictions as above. 65 66 Second and further args are passed on the stack. Padding is used 67 after QImode parameters (i.e. lower-addressed byte is the value, 68 higher-addressed byte is the padding), stack "alignment" is 16 bits. 69 70 71 Return Value 72 ============ 73 74 r8c, m16c 75 --------- 76 77 QImode in r0l 78 HImode in r0 79 near pointer in r0 80 (desired) 81 SImode in r2r0 82 far pointer in r2r0 83 (actual) 84 Anything bigger than 16 bits is returned in memory, at mem0 (mem0 85 through mem15 are provided by libgcc.a) 86 87 Aggregate values (regardless of size) are returned by pushing a 88 pointer to a temporary area on the stack after the args are pushed. 89 The function fills in this area with the value. Note that this 90 pointer on the stack does not affect how register arguments, if any, 91 are configured. 92 93 m32cm, m32c 94 ----------- 95 Same. 96 97 98 Registers Preserved Across Calls 99 ================================ 100 101 r8c, m16c 102 --------- 103 sb, fb, sp (i.e. nearly all registers are call clobbered) 104 105 m32cm, m32c 106 ----------- 107 r1, r2, r3, a0, a1, sb, fb, sp 108 (except when used for return values) 109 110 111 Interrupt Handlers 112 ================== 113 114 The stack frame is slightly different for interrupt handlers, because 115 (1) we don't have a usable parent frame, and (2) we have to use 116 special instructions to return and thus must save/restore everything 117 differently. 118 119 +-------------------- 120 | program state 121 osp -> +-------------------- 122 | return address 123 +-------------------- 124 | saved r0..fp (pushm) 125 fp -> +-------------------- 126 | local data 127 +-------------------- 128 | saved regs mem0..mem15 129 +-------------------- 130 | outgoing args (opt) 131 sp -> +-------------------- 132 133
Indexes created Sun Mar 01 05:31:48 UTC 2026