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// Copyright 2018 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "textflag.h"
// handleMemcpyFault returns (the value stored in AX, the value stored in DI).
// Control is transferred to it when memcpy below receives SIGSEGV or SIGBUS,
// with the faulting address stored in AX and the signal number stored in DI.
//
// It must have the same frame configuration as memcpy so that it can undo any
// potential call frame set up by the assembler.
TEXT handleMemcpyFault(SB), NOSPLIT, $0-36
MOVQ AX, addr+24(FP)
MOVL DI, sig+32(FP)
RET
// memcpy copies data from src to dst. If a SIGSEGV or SIGBUS signal is received
// during the copy, it returns the address that caused the fault and the number
// of the signal that was received. Otherwise, it returns an unspecified address
// and a signal number of 0.
//
// Data is copied in order, such that if a fault happens at address p, it is
// safe to assume that all data before p-maxRegisterSize has already been
// successfully copied.
//
// The code is derived from the forward copying part of runtime.memmove.
//
// func memcpy(dst, src unsafe.Pointer, n uintptr) (fault unsafe.Pointer, sig int32)
TEXT ·memcpy(SB), NOSPLIT, $0-36
// Store 0 as the returned signal number. If we run to completion,
// this is the value the caller will see; if a signal is received,
// handleMemcpyFault will store a different value in this address.
MOVL $0, sig+32(FP)
MOVQ to+0(FP), DI
MOVQ from+8(FP), SI
MOVQ n+16(FP), BX
// REP instructions have a high startup cost, so we handle small sizes
// with some straightline code. The REP MOVSQ instruction is really fast
// for large sizes. The cutover is approximately 2K.
tail:
// move_129through256 or smaller work whether or not the source and the
// destination memory regions overlap because they load all data into
// registers before writing it back. move_256through2048 on the other
// hand can be used only when the memory regions don't overlap or the copy
// direction is forward.
TESTQ BX, BX
JEQ move_0
CMPQ BX, $2
JBE move_1or2
CMPQ BX, $4
JBE move_3or4
CMPQ BX, $8
JB move_5through7
JE move_8
CMPQ BX, $16
JBE move_9through16
CMPQ BX, $32
JBE move_17through32
CMPQ BX, $64
JBE move_33through64
CMPQ BX, $128
JBE move_65through128
CMPQ BX, $256
JBE move_129through256
// TODO: use branch table and BSR to make this just a single dispatch
/*
* forward copy loop
*/
CMPQ BX, $2048
JLS move_256through2048
// Check alignment
MOVL SI, AX
ORL DI, AX
TESTL $7, AX
JEQ fwdBy8
// Do 1 byte at a time
MOVQ BX, CX
REP; MOVSB
RET
fwdBy8:
// Do 8 bytes at a time
MOVQ BX, CX
SHRQ $3, CX
ANDQ $7, BX
REP; MOVSQ
JMP tail
move_1or2:
MOVB (SI), AX
MOVB AX, (DI)
MOVB -1(SI)(BX*1), CX
MOVB CX, -1(DI)(BX*1)
RET
move_0:
RET
move_3or4:
MOVW (SI), AX
MOVW AX, (DI)
MOVW -2(SI)(BX*1), CX
MOVW CX, -2(DI)(BX*1)
RET
move_5through7:
MOVL (SI), AX
MOVL AX, (DI)
MOVL -4(SI)(BX*1), CX
MOVL CX, -4(DI)(BX*1)
RET
move_8:
// We need a separate case for 8 to make sure we write pointers atomically.
MOVQ (SI), AX
MOVQ AX, (DI)
RET
move_9through16:
MOVQ (SI), AX
MOVQ AX, (DI)
MOVQ -8(SI)(BX*1), CX
MOVQ CX, -8(DI)(BX*1)
RET
move_17through32:
MOVOU (SI), X0
MOVOU X0, (DI)
MOVOU -16(SI)(BX*1), X1
MOVOU X1, -16(DI)(BX*1)
RET
move_33through64:
MOVOU (SI), X0
MOVOU X0, (DI)
MOVOU 16(SI), X1
MOVOU X1, 16(DI)
MOVOU -32(SI)(BX*1), X2
MOVOU X2, -32(DI)(BX*1)
MOVOU -16(SI)(BX*1), X3
MOVOU X3, -16(DI)(BX*1)
RET
move_65through128:
MOVOU (SI), X0
MOVOU X0, (DI)
MOVOU 16(SI), X1
MOVOU X1, 16(DI)
MOVOU 32(SI), X2
MOVOU X2, 32(DI)
MOVOU 48(SI), X3
MOVOU X3, 48(DI)
MOVOU -64(SI)(BX*1), X4
MOVOU X4, -64(DI)(BX*1)
MOVOU -48(SI)(BX*1), X5
MOVOU X5, -48(DI)(BX*1)
MOVOU -32(SI)(BX*1), X6
MOVOU X6, -32(DI)(BX*1)
MOVOU -16(SI)(BX*1), X7
MOVOU X7, -16(DI)(BX*1)
RET
move_129through256:
MOVOU (SI), X0
MOVOU X0, (DI)
MOVOU 16(SI), X1
MOVOU X1, 16(DI)
MOVOU 32(SI), X2
MOVOU X2, 32(DI)
MOVOU 48(SI), X3
MOVOU X3, 48(DI)
MOVOU 64(SI), X4
MOVOU X4, 64(DI)
MOVOU 80(SI), X5
MOVOU X5, 80(DI)
MOVOU 96(SI), X6
MOVOU X6, 96(DI)
MOVOU 112(SI), X7
MOVOU X7, 112(DI)
MOVOU -128(SI)(BX*1), X8
MOVOU X8, -128(DI)(BX*1)
MOVOU -112(SI)(BX*1), X9
MOVOU X9, -112(DI)(BX*1)
MOVOU -96(SI)(BX*1), X10
MOVOU X10, -96(DI)(BX*1)
MOVOU -80(SI)(BX*1), X11
MOVOU X11, -80(DI)(BX*1)
MOVOU -64(SI)(BX*1), X12
MOVOU X12, -64(DI)(BX*1)
MOVOU -48(SI)(BX*1), X13
MOVOU X13, -48(DI)(BX*1)
MOVOU -32(SI)(BX*1), X14
MOVOU X14, -32(DI)(BX*1)
MOVOU -16(SI)(BX*1), X15
MOVOU X15, -16(DI)(BX*1)
RET
move_256through2048:
SUBQ $256, BX
MOVOU (SI), X0
MOVOU X0, (DI)
MOVOU 16(SI), X1
MOVOU X1, 16(DI)
MOVOU 32(SI), X2
MOVOU X2, 32(DI)
MOVOU 48(SI), X3
MOVOU X3, 48(DI)
MOVOU 64(SI), X4
MOVOU X4, 64(DI)
MOVOU 80(SI), X5
MOVOU X5, 80(DI)
MOVOU 96(SI), X6
MOVOU X6, 96(DI)
MOVOU 112(SI), X7
MOVOU X7, 112(DI)
MOVOU 128(SI), X8
MOVOU X8, 128(DI)
MOVOU 144(SI), X9
MOVOU X9, 144(DI)
MOVOU 160(SI), X10
MOVOU X10, 160(DI)
MOVOU 176(SI), X11
MOVOU X11, 176(DI)
MOVOU 192(SI), X12
MOVOU X12, 192(DI)
MOVOU 208(SI), X13
MOVOU X13, 208(DI)
MOVOU 224(SI), X14
MOVOU X14, 224(DI)
MOVOU 240(SI), X15
MOVOU X15, 240(DI)
CMPQ BX, $256
LEAQ 256(SI), SI
LEAQ 256(DI), DI
JGE move_256through2048
JMP tail
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