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