169 lines
6.7 KiB
C
169 lines
6.7 KiB
C
/****************************************************************************
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* arch/xtensa/include/xtensa/xtensa_abi.h
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*
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* Adapted from use in NuttX by:
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*
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* Copyright (C) 2016 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Derives from logic originally provided by Cadence Design Systems Inc.
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*
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* Copyright (c) 2006-2015 Cadence Design Systems Inc.
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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****************************************************************************/
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#ifndef __ARCH_XTENSA_INCLUDE_XTENSA_XTENSA_ABI_H
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#define __ARCH_XTENSA_INCLUDE_XTENSA_XTENSA_ABI_H
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/* Windowed ABI
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*
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* The Windowed Register Option replaces the simple 16-entry AR register
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* file with a larger register file from which a window of 16 entries is
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* visible at any given time. The window is rotated on subroutine entry
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* and exit, automatically saving and restoring some registers. When the
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* window is rotated far enough to require registers to be saved to or
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* restored from the program stack, an exception is raised to move some
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* of the register values between the register file and the program stack.
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*
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* Windowed Register Usage:
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* ---------------- ----------------------------------
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* Callee Register Usage
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* Register Name
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* ---------------- ----------------------------------
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* a0 Return address
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* a1/sp Stack pointer
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* a2..a7 In, out, inout, and return values
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* ---------------- ----------------------------------
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*
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* Calls to routines that use only a2..a3 as parameters may use the CALL4,
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* CALL8, or CALL12 instructions to save 4, 8, or 12 live registers. Calls
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* to routines that use a2..a7 for parameters may use only CALL8 or CALL12.
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*
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* Arguments are passed in both registers and memory. The first six
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* incoming arguments are stored in registers a2 through a7, and additional
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* arguments are stored on the stack starting at the current stack pointer
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* a1. Because Xtensa uses register windows that rotate during a function
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* call, outgoing arguments that will become the incoming arguments must be
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* stored to different register numbers. Depending on the call instruction
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* and, thus, the rotation of the register window, the arguments are passed
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* starting starting with register a(2+N), where N is the size of the
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* window rotation.
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* Therefore, the first argument in case of a call4 instruction is placed
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* into a6, and for a call8 instruction into a10. Large arguments (8-bytes)
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* are always passed in an even/odd register pair even if that means to
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* omit a register for alignment. The return values are stored in a2
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* through a7.
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*
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* return addr stack ptr arg0, arg1, arg2, arg3, arg4, arg5
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* ----------- --------- ----------------------------------
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* a0 a1 a2, a3, a4, a5, a6, a7
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*
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* call4 a4 a5 a6, a7, a8, a9, a10, a11
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* call8 a8 a9 a10, a11, a12, a13, a14, a15
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* call12 a12 a13 a14, a15 --- --- --- ---
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*
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* The stack pointer SP should only be modified by ENTRY and MOVSP
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* instructions (except for initialization and restoration). If some other
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* instruction modifies SP, any values in the register-spill area will not
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* be moved.
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*
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* Call 0 ABI
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*
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* CALL0 AR Register Usage
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* ---------------- ----------------------------------
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* Callee Register Usage
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* Register Name
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* ---------------- ----------------------------------
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* a0 Return Address
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* a1/sp Stack pointer
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* a2..a7 In, out, inout, and return values
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* a8 Static Chain
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* a12..a15 Callee-saved
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* a15 Stack-Frame Pointer (optional)
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*
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* a0, a2-a11 Caller-saved
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* a1, a12..a15 Callee-saved
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* ---------------- ----------------------------------
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*
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* CALL0 is used. The return address is placed in A0 and the CPU simply
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* jumps to the CALL0 function entry point.
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*/
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/* MACROS TO HANDLE ABI SPECIFICS OF FUNCTION ENTRY AND RETURN
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*
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* Convenient where the frame size requirements are the same for both ABIs.
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* ENTRY(sz), RET(sz) are for framed functions (have locals or make calls).
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* ENTRY0, RET0 are for frameless functions (no locals, no calls).
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*
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* where size = size of stack frame in bytes (must be >0 and aligned to 16).
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* For framed functions the frame is created and the return address saved at
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* base of frame (Call0 ABI) or as determined by hardware (Windowed ABI).
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* For frameless functions, there is no frame and return address remains in
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* a0.
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* Note: Because CPP macros expand to a single line, macros requiring
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* multi-line expansions are implemented as assembler macros.
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*/
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#ifdef __ASSEMBLY__
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/* Function prologues and epilogues */
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#ifdef __XTENSA_CALL0_ABI__
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/* Call0 */
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.macro entry1 size=0x10
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addi sp, sp, -\size
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s32i a0, sp, 0
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.endm
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.macro ret1 size=0x10
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l32i a0, sp, 0
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addi sp, sp, \size
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ret
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.endm
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# define ENTRY(sz) entry1 sz
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# define ENTRY0
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# define RET(sz) ret1 sz
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# define RET0 ret
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#else
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/* Windowed */
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# define ENTRY(sz) entry sp, sz
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# define ENTRY0 entry sp, 0x10
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# define RET(sz) retw
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# define RET0 retw
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#endif
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/* Index into stack frame (skipping over saved A0) */
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#define LOCAL_OFFSET(n) ((n) << 2) /* n = 1 .. ((size >> 2) - 1) */
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#endif /* __ASSEMBLY_ */
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#endif /* __ARCH_XTENSA_INCLUDE_XTENSA_XTENSA_ABI_H */
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