memclr_loong64.s

Documentation: runtime

     1// Copyright 2022 The Go Authors. All rights reserved.
     2// Use of this source code is governed by a BSD-style
     3// license that can be found in the LICENSE file.
     4
     5#include "go_asm.h"
     6#include "textflag.h"
     7
     8// Register map
     9//
    10// R4: ptr
    11// R5: n
    12// R6: ptrend
    13// R7: tmp
    14
    15// Algorithm:
    16//
    17// 1. when count <= 64 bytes, memory alignment check is omitted.
    18// The handling is divided into distinct cases based on the size
    19// of count: clr_0, clr_1, clr_2, clr_3, clr_4, clr_5through7,
    20// clr_8, clr_9through16, clr_17through32, and clr_33through64.
    21//
    22// 2. when count > 64 bytes, memory alignment check is performed.
    23// Unaligned bytes are processed first (that is, 8-(ptr&7)), and
    24// then a 64-byte loop is executed to zero out memory.
    25// When the number of remaining bytes not cleared is n < 64 bytes,
    26// a tail processing is performed, invoking the corresponding case
    27// based on the size of n.
    28//
    29//    ptr           newptr                           ptrend
    30//     |               |<----count after correction---->|
    31//     |<-------------count before correction---------->|
    32//     |<--8-(ptr&7)-->|               |<---64 bytes--->|
    33//     +------------------------------------------------+
    34//     |   Head        |      Body     |      Tail      |
    35//     +---------------+---------------+----------------+
    36//    newptr = ptr - (ptr & 7) + 8
    37//    count = count - 8 + (ptr & 7)
    38
    39// func memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr)
    40TEXT runtime·memclrNoHeapPointers<ABIInternal>(SB),NOSPLIT,$0-16
    41	BEQ	R5, clr_0
    42	ADDV	R4, R5, R6
    43
    44tail:
    45	// <=64 bytes, clear directly, not check aligned
    46	SGTU	$2, R5, R7
    47	BNE	R7, clr_1
    48	SGTU	$3, R5, R7
    49	BNE	R7, clr_2
    50	SGTU	$4, R5, R7
    51	BNE	R7, clr_3
    52	SGTU	$5, R5, R7
    53	BNE	R7, clr_4
    54	SGTU	$8, R5, R7
    55	BNE	R7, clr_5through7
    56	SGTU	$9, R5, R7
    57	BNE	R7, clr_8
    58	SGTU	$17, R5, R7
    59	BNE	R7, clr_9through16
    60	SGTU	$33, R5, R7
    61	BNE	R7, clr_17through32
    62	SGTU	$65, R5, R7
    63	BNE	R7, clr_33through64
    64
    65	// n > 64 bytes, check aligned
    66	AND	$7, R4, R7
    67	BEQ	R7, body
    68
    69head:
    70	MOVV	R0, (R4)
    71	SUBV	R7, R4
    72	ADDV	R7, R5
    73	ADDV	$8, R4	// newptr = ptr + (8 - (ptr & 7))
    74	SUBV	$8, R5	// newn = n - (8 - (ptr & 7))
    75	SGTU	$65, R5, R7
    76	BNE	R7, clr_33through64
    77
    78body:
    79	MOVV	R0, (R4)
    80	MOVV	R0, 8(R4)
    81	MOVV	R0, 16(R4)
    82	MOVV	R0, 24(R4)
    83	MOVV	R0, 32(R4)
    84	MOVV	R0, 40(R4)
    85	MOVV	R0, 48(R4)
    86	MOVV	R0, 56(R4)
    87	ADDV	$-64, R5
    88	ADDV	$64, R4
    89	SGTU	$65, R5, R7
    90	BEQ	R7, body
    91	BEQ	R5, clr_0
    92	JMP	tail
    93
    94clr_0:
    95	RET
    96clr_1:
    97	MOVB	R0, (R4)
    98	RET
    99clr_2:
   100	MOVH	R0, (R4)
   101	RET
   102clr_3:
   103	MOVH	R0, (R4)
   104	MOVB	R0, 2(R4)
   105	RET
   106clr_4:
   107	MOVW	R0, (R4)
   108	RET
   109clr_5through7:
   110	MOVW	R0, (R4)
   111	MOVW	R0, -4(R6)
   112	RET
   113clr_8:
   114	MOVV	R0, (R4)
   115	RET
   116clr_9through16:
   117	MOVV	R0, (R4)
   118	MOVV	R0, -8(R6)
   119	RET
   120clr_17through32:
   121	MOVV	R0, (R4)
   122	MOVV	R0, 8(R4)
   123	MOVV	R0, -16(R6)
   124	MOVV	R0, -8(R6)
   125	RET
   126clr_33through64:
   127	MOVV	R0, (R4)
   128	MOVV	R0, 8(R4)
   129	MOVV	R0, 16(R4)
   130	MOVV	R0, 24(R4)
   131	MOVV	R0, -32(R6)
   132	MOVV	R0, -24(R6)
   133	MOVV	R0, -16(R6)
   134	MOVV	R0, -8(R6)
   135	RET
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