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// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "textflag.h"
// handleMemclrFault returns (the value stored in R0, the value stored in R1).
// Control is transferred to it when memclr below receives SIGSEGV or SIGBUS,
// with the faulting address stored in R0 and the signal number stored in R1.
//
// It must have the same frame configuration as memclr so that it can undo any
// potential call frame set up by the assembler.
TEXT handleMemclrFault(SB), NOSPLIT, $0-28
MOVD R0, addr+16(FP)
MOVW R1, sig+24(FP)
RET
// See the corresponding doc in safecopy_unsafe.go
//
// The code is derived from runtime.memclrNoHeapPointers.
//
// func memclr(ptr unsafe.Pointer, n uintptr) (fault unsafe.Pointer, sig int32)
TEXT ·memclr(SB), NOSPLIT, $0-28
// 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,
// handleMemclrFault will store a different value in this address.
MOVW $0, sig+24(FP)
MOVD ptr+0(FP), R0
MOVD n+8(FP), R1
// If size is less than 16 bytes, use tail_zero to zero what remains
CMP $16, R1
BLT tail_zero
// Get buffer offset into 16 byte aligned address for better performance
ANDS $15, R0, ZR
BNE unaligned_to_16
aligned_to_16:
LSR $4, R1, R2
zero_by_16:
STP.P (ZR, ZR), 16(R0) // Store pair with post index.
SUBS $1, R2, R2
BNE zero_by_16
ANDS $15, R1, R1
BEQ end
// Zero buffer with size=R1 < 16
tail_zero:
TBZ $3, R1, tail_zero_4
MOVD.P ZR, 8(R0)
tail_zero_4:
TBZ $2, R1, tail_zero_2
MOVW.P ZR, 4(R0)
tail_zero_2:
TBZ $1, R1, tail_zero_1
MOVH.P ZR, 2(R0)
tail_zero_1:
TBZ $0, R1, end
MOVB ZR, (R0)
end:
RET
unaligned_to_16:
MOVD R0, R2
head_loop:
MOVBU.P ZR, 1(R0)
ANDS $15, R0, ZR
BNE head_loop
// Adjust length for what remains
SUB R2, R0, R3
SUB R3, R1
// If size is less than 16 bytes, use tail_zero to zero what remains
CMP $16, R1
BLT tail_zero
B aligned_to_16
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