244 lines
10 KiB
ArmAsm
244 lines
10 KiB
ArmAsm
/*
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* Copyright (c) 2016 Cadence Design Systems, Inc.
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* Copyright (c) 2022 Intel Corporation
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <xtensa/coreasm.h>
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#include <zephyr/zsr.h>
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/* WINDOW OVERFLOW AND UNDERFLOW EXCEPTION VECTORS AND ALLOCA EXCEPTION
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* HANDLER
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*
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* Here is the code for each window overflow/underflow exception vector and
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* (interspersed) efficient code for handling the alloca exception cause.
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* Window exceptions are handled entirely in the vector area and are very tight
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* for performance. The alloca exception is also handled entirely in the window
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* vector area so comes at essentially no cost in code size. Users should never
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* need to modify them and Cadence Design Systems recommends they do not.
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*
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* Window handlers go at predetermined vector locations according to the Xtensa
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* hardware configuration, which is ensured by their placement in a special
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* section known to the Xtensa linker support package (LSP). Since their
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* offsets in that section are always the same, the LSPs do not define a
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* section per vector.
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*
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* These things are coded for XEA2 only (XEA1 is not supported).
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*
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* Note on Underflow Handlers:
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*
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* The underflow handler for returning from call[i+1] to call[i] must preserve
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* all the registers from call[i+1]'s window. In particular, a0 and a1 must be
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* preserved because the RETW instruction will be reexecuted (and may even
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* underflow if an intervening exception has flushed call[i]'s registers).
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* Registers a2 and up may contain return values.
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*/
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#if XCHAL_HAVE_WINDOWED
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.section .WindowVectors.text, "ax"
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/* Window Overflow Exception for Call4.
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*
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* Invoked if a call[i] referenced a register (a4-a15)
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* that contains data from ancestor call[j];
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* call[j] had done a call4 to call[j+1].
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* On entry here:
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* window rotated to call[j] start point;
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* a0-a3 are registers to be saved;
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* a4-a15 must be preserved;
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* a5 is call[j+1]'s stack pointer.
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*/
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.org 0x0
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.global _WindowOverflow4
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_WindowOverflow4:
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s32e a0, a5, -16 /* save a0 to call[j+1]'s stack frame */
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s32e a1, a5, -12 /* save a1 to call[j+1]'s stack frame */
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s32e a2, a5, -8 /* save a2 to call[j+1]'s stack frame */
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s32e a3, a5, -4 /* save a3 to call[j+1]'s stack frame */
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rfwo /* rotates back to call[i] position */
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/* Window Underflow Exception for Call4
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*
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* Invoked by RETW returning from call[i+1] to call[i]
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* where call[i]'s registers must be reloaded (not live in ARs);
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* where call[i] had done a call4 to call[i+1].
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* On entry here:
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* window rotated to call[i] start point;
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* a0-a3 are undefined, must be reloaded with call[i].reg[0..3];
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* a4-a15 must be preserved (they are call[i+1].reg[0..11]);
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* a5 is call[i+1]'s stack pointer.
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*/
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.org 0x40
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.global _WindowUnderflow4
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_WindowUnderflow4:
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l32e a0, a5, -16 /* restore a0 from call[i+1]'s stack frame */
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l32e a1, a5, -12 /* restore a1 from call[i+1]'s stack frame */
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l32e a2, a5, -8 /* restore a2 from call[i+1]'s stack frame */
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l32e a3, a5, -4 /* restore a3 from call[i+1]'s stack frame */
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rfwu
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/* Handle alloca exception generated by interruptee executing 'movsp'.
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* This uses space between the window vectors, so is essentially
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* "free". All interruptee's regs are intact except a0 which is saved
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* in $ZSR_A0SAVE (assigned at build time, see gen_zsr.py for
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* details), and PS.EXCM has been set by the exception hardware (can't
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* be interrupted). The fact the alloca exception was taken means the
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* registers associated with the base-save area have been spilled and
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* will be restored by the underflow handler, so those 4 registers are
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* available for scratch. The code is optimized to avoid unaligned
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* branches and minimize cache misses.
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*/
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.align 4
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.global _xt_alloca_exc
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_xt_alloca_exc:
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rsr a0, WINDOWBASE /* grab WINDOWBASE before rotw changes it */
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rotw -1 /* WINDOWBASE goes to a4, new a0-a3 are scratch */
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rsr a2, PS
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extui a3, a2, XCHAL_PS_OWB_SHIFT, XCHAL_PS_OWB_BITS
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xor a3, a3, a4 /* bits changed from old to current windowbase */
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rsr a4, ZSR_A0SAVE /* restore original a0 (now in a4) */
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slli a3, a3, XCHAL_PS_OWB_SHIFT
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xor a2, a2, a3 /* flip changed bits in old window base */
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wsr a2, PS /* update PS.OWB to new window base */
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rsync
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_bbci.l a4, 31, _WindowUnderflow4
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rotw -1 /* original a0 goes to a8 */
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_bbci.l a8, 30, _WindowUnderflow8
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rotw -1
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j _WindowUnderflow12
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/* Window Overflow Exception for Call8
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*
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* Invoked if a call[i] referenced a register (a4-a15)
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* that contains data from ancestor call[j];
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* call[j] had done a call8 to call[j+1].
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* On entry here:
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* window rotated to call[j] start point;
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* a0-a7 are registers to be saved;
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* a8-a15 must be preserved;
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* a9 is call[j+1]'s stack pointer.
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*/
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.org 0x80
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.global _WindowOverflow8
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_WindowOverflow8:
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s32e a0, a9, -16 /* save a0 to call[j+1]'s stack frame */
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l32e a0, a1, -12 /* a0 <- call[j-1]'s sp
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(used to find end of call[j]'s frame) */
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s32e a1, a9, -12 /* save a1 to call[j+1]'s stack frame */
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s32e a2, a9, -8 /* save a2 to call[j+1]'s stack frame */
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s32e a3, a9, -4 /* save a3 to call[j+1]'s stack frame */
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s32e a4, a0, -32 /* save a4 to call[j]'s stack frame */
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s32e a5, a0, -28 /* save a5 to call[j]'s stack frame */
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s32e a6, a0, -24 /* save a6 to call[j]'s stack frame */
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s32e a7, a0, -20 /* save a7 to call[j]'s stack frame */
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rfwo /* rotates back to call[i] position */
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/*
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* Window Underflow Exception for Call8
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*
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* Invoked by RETW returning from call[i+1] to call[i]
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* where call[i]'s registers must be reloaded (not live in ARs);
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* where call[i] had done a call8 to call[i+1].
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* On entry here:
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* window rotated to call[i] start point;
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* a0-a7 are undefined, must be reloaded with call[i].reg[0..7];
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* a8-a15 must be preserved (they are call[i+1].reg[0..7]);
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* a9 is call[i+1]'s stack pointer.
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*/
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.org 0xC0
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.global _WindowUnderflow8
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_WindowUnderflow8:
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l32e a0, a9, -16 /* restore a0 from call[i+1]'s stack frame */
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l32e a1, a9, -12 /* restore a1 from call[i+1]'s stack frame */
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l32e a2, a9, -8 /* restore a2 from call[i+1]'s stack frame */
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l32e a7, a1, -12 /* a7 <- call[i-1]'s sp
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(used to find end of call[i]'s frame) */
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l32e a3, a9, -4 /* restore a3 from call[i+1]'s stack frame */
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l32e a4, a7, -32 /* restore a4 from call[i]'s stack frame */
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l32e a5, a7, -28 /* restore a5 from call[i]'s stack frame */
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l32e a6, a7, -24 /* restore a6 from call[i]'s stack frame */
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l32e a7, a7, -20 /* restore a7 from call[i]'s stack frame */
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rfwu
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/*
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* Window Overflow Exception for Call12
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*
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* Invoked if a call[i] referenced a register (a4-a15)
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* that contains data from ancestor call[j];
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* call[j] had done a call12 to call[j+1].
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* On entry here:
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* window rotated to call[j] start point;
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* a0-a11 are registers to be saved;
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* a12-a15 must be preserved;
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* a13 is call[j+1]'s stack pointer.
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*/
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.org 0x100
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.global _WindowOverflow12
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_WindowOverflow12:
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s32e a0, a13, -16 /* save a0 to call[j+1]'s stack frame */
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l32e a0, a1, -12 /* a0 <- call[j-1]'s sp
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(used to find end of call[j]'s frame) */
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s32e a1, a13, -12 /* save a1 to call[j+1]'s stack frame */
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s32e a2, a13, -8 /* save a2 to call[j+1]'s stack frame */
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s32e a3, a13, -4 /* save a3 to call[j+1]'s stack frame */
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s32e a4, a0, -48 /* save a4 to end of call[j]'s stack frame */
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s32e a5, a0, -44 /* save a5 to end of call[j]'s stack frame */
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s32e a6, a0, -40 /* save a6 to end of call[j]'s stack frame */
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s32e a7, a0, -36 /* save a7 to end of call[j]'s stack frame */
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s32e a8, a0, -32 /* save a8 to end of call[j]'s stack frame */
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s32e a9, a0, -28 /* save a9 to end of call[j]'s stack frame */
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s32e a10, a0, -24 /* save a10 to end of call[j]'s stack frame */
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s32e a11, a0, -20 /* save a11 to end of call[j]'s stack frame */
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rfwo /* rotates back to call[i] position */
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/*
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* Window Underflow Exception for Call12
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*
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* Invoked by RETW returning from call[i+1] to call[i]
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* where call[i]'s registers must be reloaded (not live in ARs);
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* where call[i] had done a call12 to call[i+1].
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* On entry here:
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* window rotated to call[i] start point;
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* a0-a11 are undefined, must be reloaded with call[i].reg[0..11];
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* a12-a15 must be preserved (they are call[i+1].reg[0..3]);
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* a13 is call[i+1]'s stack pointer.
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*/
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.org 0x140
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.global _WindowUnderflow12
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_WindowUnderflow12:
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l32e a0, a13, -16 /* restore a0 from call[i+1]'s stack frame */
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l32e a1, a13, -12 /* restore a1 from call[i+1]'s stack frame */
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l32e a2, a13, -8 /* restore a2 from call[i+1]'s stack frame */
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l32e a11, a1, -12 /* a11 <- call[i-1]'s sp
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* (used to find end of call[i]'s frame) */
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l32e a3, a13, -4 /* restore a3 from call[i+1]'s stack frame */
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l32e a4, a11, -48 /* restore a4 from end of call[i]'s stack frame */
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l32e a5, a11, -44 /* restore a5 from end of call[i]'s stack frame */
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l32e a6, a11, -40 /* restore a6 from end of call[i]'s stack frame */
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l32e a7, a11, -36 /* restore a7 from end of call[i]'s stack frame */
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l32e a8, a11, -32 /* restore a8 from end of call[i]'s stack frame */
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l32e a9, a11, -28 /* restore a9 from end of call[i]'s stack frame */
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l32e a10, a11, -24 /* restore a10 from end of call[i]'s stack
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* frame */
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l32e a11, a11, -20 /* restore a11 from end of call[i]'s stack
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* frame */
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rfwu
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#endif /* XCHAL_HAVE_WINDOWED */
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