253 lines
6.5 KiB
ArmAsm
253 lines
6.5 KiB
ArmAsm
/* setjmp/longjmp functions for Xtensa.
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Copyright (c) 2001-2006 by Tensilica Inc.
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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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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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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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/* Windowed ABI:
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This implementation relies heavily on the Xtensa register window
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mechanism. Setjmp flushes all the windows except its own to the
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stack and then copies registers from the save areas on the stack
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into the jmp_buf structure, along with the return address of the call
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to setjmp. Longjmp invalidates all the windows except its own, and
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then sets things up so that it will return to the right place,
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using a window underflow to automatically restore the registers.
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Note that it would probably be sufficient to only copy the
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registers from setjmp's caller into jmp_buf. However, we also copy
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the save area located at the stack pointer of setjmp's caller.
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This save area will typically remain intact until the longjmp call.
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The one exception is when there is an intervening alloca in
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setjmp's caller. This is certainly an unusual situation and is
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likely to cause problems in any case (the storage allocated on the
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stack cannot be safely accessed following the longjmp). As bad as
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it is, on most systems this situation would not necessarily lead to
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a catastrophic failure. If we did not preserve the extra save area
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on Xtensa, however, it would. When setjmp's caller returns after a
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longjmp, there will be a window underflow; an invalid return
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address or stack pointer in the save area will almost certainly
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lead to a crash. Keeping a copy of the extra save area in the
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jmp_buf avoids this with only a small additional cost. If setjmp
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and longjmp are ever time-critical, this could be removed.
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Call0 ABI:
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Much like other ABIs, this version just saves the necessary registers
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to the stack and restores them later. Much less needs to be done. */
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#include "xtensa-asm.h"
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#define SYS_nop 0
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#if XCHAL_HAVE_WINDOWED && !__XTENSA_CALL0_ABI__
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/* int setjmp (jmp_buf env) */
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.text
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.align 4
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.literal_position
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.global setjmp
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.type setjmp, @function
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setjmp:
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entry sp, 16
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/* Flush registers. */
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mov a4, a2 // save a2 (jmp_buf)
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movi a2, SYS_nop
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syscall
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mov a2, a4 // restore a2
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/* Copy the register save area at (sp - 16). */
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addi a5, a1, -16
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l32i a3, a5, 0
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l32i a4, a5, 4
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s32i a3, a2, 0
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s32i a4, a2, 4
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l32i a3, a5, 8
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l32i a4, a5, 12
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s32i a3, a2, 8
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s32i a4, a2, 12
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/* Copy 0-8 words from the register overflow area. */
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extui a3, a0, 30, 2
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blti a3, 2, .Lendsj
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l32i a7, a1, 4
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slli a4, a3, 4
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sub a5, a7, a4
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addi a6, a2, 16
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addi a7, a7, -16 // a7 = end of register overflow area
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.Lsjloop:
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l32i a3, a5, 0
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l32i a4, a5, 4
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s32i a3, a6, 0
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s32i a4, a6, 4
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l32i a3, a5, 8
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l32i a4, a5, 12
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s32i a3, a6, 8
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s32i a4, a6, 12
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addi a5, a5, 16
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addi a6, a6, 16
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blt a5, a7, .Lsjloop
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.Lendsj:
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/* Copy the register save area at sp. */
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l32i a3, a1, 0
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l32i a4, a1, 4
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s32i a3, a2, 48
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s32i a4, a2, 52
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l32i a3, a1, 8
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l32i a4, a1, 12
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s32i a3, a2, 56
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s32i a4, a2, 60
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/* Save the return address, including the window size bits. */
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s32i a0, a2, 64
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movi a2, 0
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retw
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.size setjmp, . - setjmp
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/* void longjmp (jmp_buf env, int val) */
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.align 4
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.literal_position
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.global longjmp
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.type longjmp, @function
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longjmp:
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entry sp, 16
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/* a2 == &env, a3 == val */
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/* Invalidate all but the current window;
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set WindowStart to (1 << WindowBase). */
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rsr a5, WINDOWBASE
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movi a4, 1
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ssl a5
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sll a4, a4
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wsr a4, WINDOWSTART
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rsync
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/* Return to the return address of the setjmp, using the
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window size bits from the setjmp call so that the caller
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will be able to find the return value that we put in a2. */
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l32i a0, a2, 64
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/* Copy the first 4 saved registers from jmp_buf into the save area
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at the current sp so that the values will be restored to registers
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when longjmp returns. */
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addi a7, a1, -16
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l32i a4, a2, 0
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l32i a5, a2, 4
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s32i a4, a7, 0
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s32i a5, a7, 4
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l32i a4, a2, 8
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l32i a5, a2, 12
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s32i a4, a7, 8
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s32i a5, a7, 12
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/* Copy the remaining 0-8 saved registers. */
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extui a7, a0, 30, 2
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blti a7, 2, .Lendlj
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l32i a8, a2, 52
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slli a4, a7, 4
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sub a6, a8, a4
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addi a5, a2, 16
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addi a8, a8, -16 // a8 = end of register overflow area
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.Lljloop:
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l32i a7, a5, 0
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l32i a4, a5, 4
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s32i a7, a6, 0
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s32i a4, a6, 4
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l32i a7, a5, 8
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l32i a4, a5, 12
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s32i a7, a6, 8
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s32i a4, a6, 12
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addi a5, a5, 16
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addi a6, a6, 16
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blt a6, a8, .Lljloop
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.Lendlj:
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/* The 4 words saved from the register save area at the target's
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sp are copied back to the target procedure's save area. The
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only point of this is to prevent a catastrophic failure in
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case the contents were moved by an alloca after calling
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setjmp. This is a bit paranoid but it doesn't cost much. */
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l32i a7, a2, 4 // load the target stack pointer
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addi a7, a7, -16 // find the destination save area
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l32i a4, a2, 48
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l32i a5, a2, 52
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s32i a4, a7, 0
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s32i a5, a7, 4
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l32i a4, a2, 56
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l32i a5, a2, 60
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s32i a4, a7, 8
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s32i a5, a7, 12
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/* Return val ? val : 1. */
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movi a2, 1
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movnez a2, a3, a3
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retw
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.size longjmp, . - longjmp
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#else /* CALL0 ABI */
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.text
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.align 4
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.literal_position
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.global setjmp
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.type setjmp, @function
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setjmp:
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s32i a0, a2, 0
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s32i a1, a2, 4
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s32i a12, a2, 8
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s32i a13, a2, 12
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s32i a14, a2, 16
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s32i a15, a2, 20
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movi a2, 0
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ret
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.size setjmp, . - setjmp
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.align 4
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.literal_position
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.global longjmp
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.type longjmp, @function
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longjmp:
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l32i a0, a2, 0
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l32i a12, a2, 8
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l32i a13, a2, 12
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l32i a14, a2, 16
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l32i a15, a2, 20
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l32i a1, a2, 4
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/* Return val ? val : 1. */
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movi a2, 1
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movnez a2, a3, a3
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ret
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.size longjmp, .-longjmp
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#endif /* CALL0 ABI */
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