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// window-vectors-new.S - Register Window Overflow/Underflow Handlers for XEA2
// $Id: //depot/rel/Eaglenest/Xtensa/OS/xtos/window-vectors-new.S#3 $
// Copyright (c) 1999-2013 Tensilica 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.
// Exports
.global _WindowOverflow4
.global _WindowUnderflow4
.global _WindowOverflow8
.global _WindowUnderflow8
.global _WindowOverflow12
.global _WindowUnderflow12
// Note: the current window exception vectors do not generate any
// literals. Hence the literal_prefix directive is not necessary.
// Specifying it "just in case" creates an empty section (named
// ".WindowVectors.literal") which can in some cases cause linking
// problems (the linker scripts don't place it anywhere).
// So leave it commented out:
//
//.begin literal_prefix .WindowVectors
.section .WindowVectors.text, "ax"
//
// GENERAL NOTES:
//
// These window exception handlers need not be modified.
// They are specific to the windowed call ABI only.
//
// Underflow Handlers:
//
// The underflow handler for returning from call[i+1] to call[i]
// must preserve all the registers from call[i+1]'s window.
// In particular, a0 and a1 must be preserved because the RETW instruction
// will be reexecuted (and may even underflow again if an intervening
// exception has flushed call[i]'s registers).
// Registers a2 and up may contain return values.
//
// The caller could also potentially assume that the callee's a0 and a1
// (its own a4&a5 if call4, a8&a9 if call8, a12&a13 if call12)
// are correct for whatever reason (not a clean thing to do in general,
// but if it's possible, unless the ABI explicitly prohibits it,
// it will eventually be done :) -- whether the the ABI needs to
// prohibit this is a different question).
//
// Timing of Handlers:
//
// Here is an overview of the overhead of taking a window exception,
// ie. the number of additional cycles taken relative to case where
// an exception is not taken.
// NOTE: these numbers do not take into account any cache misses,
// write buffer stalls, or other external stalls, if they occur.
// The totals consist of 5 cycles to enter the handler (or 6 or 7
// for optional longer pipelines in Xtensa LX), the number of instructions
// and interlocks (2nd and 3rd columns below), and 2 cycles jump delay
// on return (3 cycles for optional longer I-side pipeline in Xtensa LX):
//
// Instruction+bubbles Totals (5-stage)
// XEA1 XEA2 XEA1 XEA2
// Overflow-4 7 5 14 12
// Overflow-8 14 10 21 17
// Overflow-12 18 14 25 21
// Underflow-4 6 5 13 12
// Underflow-8 14 10 21 17
// Underflow-12 18 14 25 21
//
// Underflow-8 15 12 25 22 (7-stage; could be made 1 less)
// Underflow-12 19 16 29 26 (7-stage; could be made 1 less)
// 4-Register Window Overflow Vector (Handler)
//
// Invoked if a call[i] referenced a register (a4-a15)
// that contains data from ancestor call[j];
// call[j] had done a call4 to call[j+1].
// On entry here:
// window rotated to call[j] start point;
// a0-a3 are registers to be saved;
// a4-a15 must be preserved;
// a5 is call[j+1]'s stack pointer.
.org 0x0
_WindowOverflow4:
s32e a0, a5, -16 // save a0 to call[j+1]'s stack frame
s32e a1, a5, -12 // save a1 to call[j+1]'s stack frame
s32e a2, a5, -8 // save a2 to call[j+1]'s stack frame
s32e a3, a5, -4 // save a3 to call[j+1]'s stack frame
rfwo // rotates back to call[i] position
.size _WindowOverflow4, . - _WindowOverflow4
// 4-Register Window Underflow Vector (Handler)
//
// Invoked by RETW returning from call[i+1] to call[i]
// where call[i]'s registers must be reloaded (not live in ARs);
// call[i] had done a call4 to call[i+1].
// On entry here:
// window rotated to call[i] start point;
// a0-a3 are undefined, must be reloaded with call[i].reg[0..3];
// a4-a15 must be preserved (they are call[i+1].reg[0..11]);
// a5 is call[i+1]'s stack pointer.
.org 0x40
_WindowUnderflow4:
l32e a0, a5, -16 // restore a0 from call[i+1]'s stack frame
l32e a1, a5, -12 // restore a1 from call[i+1]'s stack frame
l32e a2, a5, -8 // restore a2 from call[i+1]'s stack frame
l32e a3, a5, -4 // restore a3 from call[i+1]'s stack frame
rfwu
.size _WindowUnderflow4, . - _WindowUnderflow4
// 8-Register Window Overflow Vector (Handler)
//
// Invoked if a call[i] referenced a register (a4-a15)
// that contains data from ancestor call[j];
// call[j] had done a call8 to call[j+1].
// On entry here:
// window rotated to call[j] start point;
// a0-a7 are registers to be saved;
// a8-a15 must be preserved;
// a9 is call[j+1]'s stack pointer.
.org 0x80
_WindowOverflow8:
s32e a0, a9, -16 // save a0 to call[j+1]'s stack frame
l32e a0, a1, -12 // a0 <- call[j-1]'s sp (used to find end of call[j]'s frame)
s32e a1, a9, -12 // save a1 to call[j+1]'s stack frame
s32e a2, a9, -8 // save a2 to call[j+1]'s stack frame
s32e a3, a9, -4 // save a3 to call[j+1]'s stack frame
s32e a4, a0, -32 // save a4 to call[j]'s stack frame
s32e a5, a0, -28 // save a5 to call[j]'s stack frame
s32e a6, a0, -24 // save a6 to call[j]'s stack frame
s32e a7, a0, -20 // save a7 to call[j]'s stack frame
rfwo // rotates back to call[i] position
.size _WindowOverflow8, . - _WindowOverflow8
// 8-Register Window Underflow Vector (Handler)
//
// Invoked by RETW returning from call[i+1] to call[i]
// where call[i]'s registers must be reloaded (not live in ARs);
// call[i] had done a call8 to call[i+1].
// On entry here:
// window rotated to call[i] start point;
// a0-a7 are undefined, must be reloaded with call[i].reg[0..7];
// a8-a15 must be preserved (they are call[i+1].reg[0..7]);
// a9 is call[i+1]'s stack pointer.
.org 0xC0
_WindowUnderflow8:
l32e a0, a9, -16 // restore a0 from call[i+1]'s stack frame
l32e a1, a9, -12 // restore a1 from call[i+1]'s stack frame
l32e a2, a9, -8 // restore a2 from call[i+1]'s stack frame
l32e a7, a1, -12 // a7 <- call[i-1]'s sp (used to find end of call[i]'s frame)
l32e a3, a9, -4 // restore a3 from call[i+1]'s stack frame
l32e a4, a7, -32 // restore a4 from call[i]'s stack frame
l32e a5, a7, -28 // restore a5 from call[i]'s stack frame
l32e a6, a7, -24 // restore a6 from call[i]'s stack frame../../.././libgloss/xtensa/window-vectors.S
l32e a7, a7, -20 // restore a7 from call[i]'s stack frame
rfwu
.size _WindowUnderflow8, . - _WindowUnderflow8
// 12-Register Window Overflow Vector (Handler)
//
// Invoked if a call[i] referenced a register (a4-a15)
// that contains data from ancestor call[j];
// call[j] had done a call12 to call[j+1].
// On entry here:
// window rotated to call[j] start point;
// a0-a11 are registers to be saved;
// a12-a15 must be preserved;
// a13 is call[j+1]'s stack pointer.
.org 0x100
_WindowOverflow12:
s32e a0, a13, -16 // save a0 to call[j+1]'s stack frame
l32e a0, a1, -12 // a0 <- call[j-1]'s sp (used to find end of call[j]'s frame)
s32e a1, a13, -12 // save a1 to call[j+1]'s stack frame
s32e a2, a13, -8 // save a2 to call[j+1]'s stack frame
s32e a3, a13, -4 // save a3 to call[j+1]'s stack frame
s32e a4, a0, -48 // save a4 to end of call[j]'s stack frame
s32e a5, a0, -44 // save a5 to end of call[j]'s stack frame
s32e a6, a0, -40 // save a6 to end of call[j]'s stack frame
s32e a7, a0, -36 // save a7 to end of call[j]'s stack frame
s32e a8, a0, -32 // save a8 to end of call[j]'s stack frame
s32e a9, a0, -28 // save a9 to end of call[j]'s stack frame
s32e a10, a0, -24 // save a10 to end of call[j]'s stack frame
s32e a11, a0, -20 // save a11 to end of call[j]'s stack frame
rfwo // rotates back to call[i] position
.size _WindowOverflow12, . - _WindowOverflow12
// 12-Register Window Underflow Vector (Handler)
//
// Invoked by RETW returning from call[i+1] to call[i]
// where call[i]'s registers must be reloaded (not live in ARs);
// call[i] had done a call12 to call[i+1].
// On entry here:
// window rotated to call[i] start point;
// a0-a11 are undefined, must be reloaded with call[i].reg[0..11];
// a12-a15 must be preserved (they are call[i+1].reg[0..3]);
// a13 is call[i+1]'s stack pointer.
.org 0x140
_WindowUnderflow12:
l32e a0, a13, -16 // restore a0 from call[i+1]'s stack frame
l32e a1, a13, -12 // restore a1 from call[i+1]'s stack frame
l32e a2, a13, -8 // restore a2 from call[i+1]'s stack frame
l32e a11, a1, -12 // a11 <- call[i-1]'s sp (used to find end of call[i]'s frame)
l32e a3, a13, -4 // restore a3 from call[i+1]'s stack frame
l32e a4, a11, -48 // restore a4 from end of call[i]'s stack frame
l32e a5, a11, -44 // restore a5 from end of call[i]'s stack frame
l32e a6, a11, -40 // restore a6 from end of call[i]'s stack frame
l32e a7, a11, -36 // restore a7 from end of call[i]'s stack frame
l32e a8, a11, -32 // restore a8 from end of call[i]'s stack frame
l32e a9, a11, -28 // restore a9 from end of call[i]'s stack frame
l32e a10, a11, -24 // restore a10 from end of call[i]'s stack frame
l32e a11, a11, -20 // restore a11 from end of call[i]'s stack frame
rfwu
.size _WindowUnderflow12, . - _WindowUnderflow12
//.end literal_prefix
.text
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