723 lines
16 KiB
ArmAsm
723 lines
16 KiB
ArmAsm
// Copyright 2020 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build !appengine
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// +build gc
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// +build !noasm
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#include "textflag.h"
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// The asm code generally follows the pure Go code in encode_other.go, except
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// where marked with a "!!!".
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// ----------------------------------------------------------------------------
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// func emitLiteral(dst, lit []byte) int
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//
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// All local variables fit into registers. The register allocation:
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// - R3 len(lit)
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// - R4 n
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// - R6 return value
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// - R8 &dst[i]
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// - R10 &lit[0]
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//
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// The 32 bytes of stack space is to call runtime·memmove.
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//
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// The unusual register allocation of local variables, such as R10 for the
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// source pointer, matches the allocation used at the call site in encodeBlock,
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// which makes it easier to manually inline this function.
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TEXT ·emitLiteral(SB), NOSPLIT, $32-56
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MOVD dst_base+0(FP), R8
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MOVD lit_base+24(FP), R10
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MOVD lit_len+32(FP), R3
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MOVD R3, R6
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MOVW R3, R4
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SUBW $1, R4, R4
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CMPW $60, R4
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BLT oneByte
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CMPW $256, R4
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BLT twoBytes
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threeBytes:
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MOVD $0xf4, R2
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MOVB R2, 0(R8)
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MOVW R4, 1(R8)
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ADD $3, R8, R8
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ADD $3, R6, R6
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B memmove
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twoBytes:
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MOVD $0xf0, R2
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MOVB R2, 0(R8)
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MOVB R4, 1(R8)
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ADD $2, R8, R8
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ADD $2, R6, R6
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B memmove
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oneByte:
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LSLW $2, R4, R4
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MOVB R4, 0(R8)
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ADD $1, R8, R8
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ADD $1, R6, R6
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memmove:
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MOVD R6, ret+48(FP)
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// copy(dst[i:], lit)
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//
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// This means calling runtime·memmove(&dst[i], &lit[0], len(lit)), so we push
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// R8, R10 and R3 as arguments.
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MOVD R8, 8(RSP)
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MOVD R10, 16(RSP)
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MOVD R3, 24(RSP)
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CALL runtime·memmove(SB)
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RET
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// ----------------------------------------------------------------------------
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// func emitCopy(dst []byte, offset, length int) int
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//
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// All local variables fit into registers. The register allocation:
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// - R3 length
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// - R7 &dst[0]
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// - R8 &dst[i]
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// - R11 offset
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//
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// The unusual register allocation of local variables, such as R11 for the
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// offset, matches the allocation used at the call site in encodeBlock, which
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// makes it easier to manually inline this function.
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TEXT ·emitCopy(SB), NOSPLIT, $0-48
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MOVD dst_base+0(FP), R8
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MOVD R8, R7
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MOVD offset+24(FP), R11
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MOVD length+32(FP), R3
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loop0:
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// for length >= 68 { etc }
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CMPW $68, R3
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BLT step1
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// Emit a length 64 copy, encoded as 3 bytes.
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MOVD $0xfe, R2
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MOVB R2, 0(R8)
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MOVW R11, 1(R8)
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ADD $3, R8, R8
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SUB $64, R3, R3
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B loop0
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step1:
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// if length > 64 { etc }
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CMP $64, R3
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BLE step2
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// Emit a length 60 copy, encoded as 3 bytes.
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MOVD $0xee, R2
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MOVB R2, 0(R8)
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MOVW R11, 1(R8)
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ADD $3, R8, R8
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SUB $60, R3, R3
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step2:
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// if length >= 12 || offset >= 2048 { goto step3 }
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CMP $12, R3
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BGE step3
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CMPW $2048, R11
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BGE step3
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// Emit the remaining copy, encoded as 2 bytes.
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MOVB R11, 1(R8)
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LSRW $3, R11, R11
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AND $0xe0, R11, R11
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SUB $4, R3, R3
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LSLW $2, R3
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AND $0xff, R3, R3
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ORRW R3, R11, R11
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ORRW $1, R11, R11
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MOVB R11, 0(R8)
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ADD $2, R8, R8
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// Return the number of bytes written.
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SUB R7, R8, R8
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MOVD R8, ret+40(FP)
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RET
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step3:
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// Emit the remaining copy, encoded as 3 bytes.
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SUB $1, R3, R3
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AND $0xff, R3, R3
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LSLW $2, R3, R3
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ORRW $2, R3, R3
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MOVB R3, 0(R8)
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MOVW R11, 1(R8)
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ADD $3, R8, R8
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// Return the number of bytes written.
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SUB R7, R8, R8
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MOVD R8, ret+40(FP)
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RET
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// ----------------------------------------------------------------------------
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// func extendMatch(src []byte, i, j int) int
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//
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// All local variables fit into registers. The register allocation:
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// - R6 &src[0]
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// - R7 &src[j]
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// - R13 &src[len(src) - 8]
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// - R14 &src[len(src)]
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// - R15 &src[i]
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//
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// The unusual register allocation of local variables, such as R15 for a source
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// pointer, matches the allocation used at the call site in encodeBlock, which
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// makes it easier to manually inline this function.
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TEXT ·extendMatch(SB), NOSPLIT, $0-48
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MOVD src_base+0(FP), R6
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MOVD src_len+8(FP), R14
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MOVD i+24(FP), R15
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MOVD j+32(FP), R7
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ADD R6, R14, R14
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ADD R6, R15, R15
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ADD R6, R7, R7
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MOVD R14, R13
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SUB $8, R13, R13
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cmp8:
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// As long as we are 8 or more bytes before the end of src, we can load and
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// compare 8 bytes at a time. If those 8 bytes are equal, repeat.
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CMP R13, R7
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BHI cmp1
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MOVD (R15), R3
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MOVD (R7), R4
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CMP R4, R3
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BNE bsf
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ADD $8, R15, R15
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ADD $8, R7, R7
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B cmp8
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bsf:
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// If those 8 bytes were not equal, XOR the two 8 byte values, and return
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// the index of the first byte that differs.
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// RBIT reverses the bit order, then CLZ counts the leading zeros, the
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// combination of which finds the least significant bit which is set.
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// The arm64 architecture is little-endian, and the shift by 3 converts
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// a bit index to a byte index.
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EOR R3, R4, R4
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RBIT R4, R4
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CLZ R4, R4
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ADD R4>>3, R7, R7
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// Convert from &src[ret] to ret.
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SUB R6, R7, R7
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MOVD R7, ret+40(FP)
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RET
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cmp1:
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// In src's tail, compare 1 byte at a time.
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CMP R7, R14
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BLS extendMatchEnd
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MOVB (R15), R3
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MOVB (R7), R4
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CMP R4, R3
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BNE extendMatchEnd
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ADD $1, R15, R15
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ADD $1, R7, R7
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B cmp1
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extendMatchEnd:
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// Convert from &src[ret] to ret.
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SUB R6, R7, R7
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MOVD R7, ret+40(FP)
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RET
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// ----------------------------------------------------------------------------
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// func encodeBlock(dst, src []byte) (d int)
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//
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// All local variables fit into registers, other than "var table". The register
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// allocation:
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// - R3 . .
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// - R4 . .
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// - R5 64 shift
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// - R6 72 &src[0], tableSize
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// - R7 80 &src[s]
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// - R8 88 &dst[d]
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// - R9 96 sLimit
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// - R10 . &src[nextEmit]
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// - R11 104 prevHash, currHash, nextHash, offset
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// - R12 112 &src[base], skip
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// - R13 . &src[nextS], &src[len(src) - 8]
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// - R14 . len(src), bytesBetweenHashLookups, &src[len(src)], x
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// - R15 120 candidate
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// - R16 . hash constant, 0x1e35a7bd
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// - R17 . &table
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// - . 128 table
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//
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// The second column (64, 72, etc) is the stack offset to spill the registers
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// when calling other functions. We could pack this slightly tighter, but it's
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// simpler to have a dedicated spill map independent of the function called.
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//
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// "var table [maxTableSize]uint16" takes up 32768 bytes of stack space. An
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// extra 64 bytes, to call other functions, and an extra 64 bytes, to spill
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// local variables (registers) during calls gives 32768 + 64 + 64 = 32896.
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TEXT ·encodeBlock(SB), 0, $32896-56
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MOVD dst_base+0(FP), R8
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MOVD src_base+24(FP), R7
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MOVD src_len+32(FP), R14
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// shift, tableSize := uint32(32-8), 1<<8
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MOVD $24, R5
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MOVD $256, R6
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MOVW $0xa7bd, R16
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MOVKW $(0x1e35<<16), R16
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calcShift:
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// for ; tableSize < maxTableSize && tableSize < len(src); tableSize *= 2 {
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// shift--
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// }
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MOVD $16384, R2
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CMP R2, R6
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BGE varTable
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CMP R14, R6
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BGE varTable
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SUB $1, R5, R5
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LSL $1, R6, R6
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B calcShift
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varTable:
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// var table [maxTableSize]uint16
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//
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// In the asm code, unlike the Go code, we can zero-initialize only the
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// first tableSize elements. Each uint16 element is 2 bytes and each
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// iterations writes 64 bytes, so we can do only tableSize/32 writes
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// instead of the 2048 writes that would zero-initialize all of table's
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// 32768 bytes. This clear could overrun the first tableSize elements, but
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// it won't overrun the allocated stack size.
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ADD $128, RSP, R17
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MOVD R17, R4
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// !!! R6 = &src[tableSize]
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ADD R6<<1, R17, R6
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memclr:
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STP.P (ZR, ZR), 64(R4)
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STP (ZR, ZR), -48(R4)
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STP (ZR, ZR), -32(R4)
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STP (ZR, ZR), -16(R4)
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CMP R4, R6
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BHI memclr
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// !!! R6 = &src[0]
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MOVD R7, R6
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// sLimit := len(src) - inputMargin
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MOVD R14, R9
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SUB $15, R9, R9
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// !!! Pre-emptively spill R5, R6 and R9 to the stack. Their values don't
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// change for the rest of the function.
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MOVD R5, 64(RSP)
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MOVD R6, 72(RSP)
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MOVD R9, 96(RSP)
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// nextEmit := 0
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MOVD R6, R10
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// s := 1
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ADD $1, R7, R7
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// nextHash := hash(load32(src, s), shift)
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MOVW 0(R7), R11
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MULW R16, R11, R11
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LSRW R5, R11, R11
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outer:
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// for { etc }
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// skip := 32
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MOVD $32, R12
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// nextS := s
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MOVD R7, R13
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// candidate := 0
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MOVD $0, R15
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inner0:
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// for { etc }
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// s := nextS
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MOVD R13, R7
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// bytesBetweenHashLookups := skip >> 5
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MOVD R12, R14
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LSR $5, R14, R14
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// nextS = s + bytesBetweenHashLookups
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ADD R14, R13, R13
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// skip += bytesBetweenHashLookups
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ADD R14, R12, R12
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// if nextS > sLimit { goto emitRemainder }
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MOVD R13, R3
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SUB R6, R3, R3
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CMP R9, R3
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BHI emitRemainder
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// candidate = int(table[nextHash])
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MOVHU 0(R17)(R11<<1), R15
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// table[nextHash] = uint16(s)
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MOVD R7, R3
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SUB R6, R3, R3
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MOVH R3, 0(R17)(R11<<1)
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// nextHash = hash(load32(src, nextS), shift)
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MOVW 0(R13), R11
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MULW R16, R11
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LSRW R5, R11, R11
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// if load32(src, s) != load32(src, candidate) { continue } break
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MOVW 0(R7), R3
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MOVW (R6)(R15), R4
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CMPW R4, R3
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BNE inner0
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fourByteMatch:
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// As per the encode_other.go code:
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//
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// A 4-byte match has been found. We'll later see etc.
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// !!! Jump to a fast path for short (<= 16 byte) literals. See the comment
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// on inputMargin in encode.go.
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MOVD R7, R3
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SUB R10, R3, R3
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CMP $16, R3
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BLE emitLiteralFastPath
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// ----------------------------------------
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// Begin inline of the emitLiteral call.
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//
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// d += emitLiteral(dst[d:], src[nextEmit:s])
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MOVW R3, R4
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SUBW $1, R4, R4
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MOVW $60, R2
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CMPW R2, R4
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BLT inlineEmitLiteralOneByte
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MOVW $256, R2
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CMPW R2, R4
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BLT inlineEmitLiteralTwoBytes
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inlineEmitLiteralThreeBytes:
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MOVD $0xf4, R1
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MOVB R1, 0(R8)
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MOVW R4, 1(R8)
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ADD $3, R8, R8
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B inlineEmitLiteralMemmove
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inlineEmitLiteralTwoBytes:
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MOVD $0xf0, R1
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MOVB R1, 0(R8)
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MOVB R4, 1(R8)
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ADD $2, R8, R8
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B inlineEmitLiteralMemmove
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inlineEmitLiteralOneByte:
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LSLW $2, R4, R4
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MOVB R4, 0(R8)
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ADD $1, R8, R8
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inlineEmitLiteralMemmove:
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// Spill local variables (registers) onto the stack; call; unspill.
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//
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// copy(dst[i:], lit)
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//
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// This means calling runtime·memmove(&dst[i], &lit[0], len(lit)), so we push
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// R8, R10 and R3 as arguments.
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MOVD R8, 8(RSP)
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MOVD R10, 16(RSP)
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MOVD R3, 24(RSP)
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// Finish the "d +=" part of "d += emitLiteral(etc)".
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ADD R3, R8, R8
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MOVD R7, 80(RSP)
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MOVD R8, 88(RSP)
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MOVD R15, 120(RSP)
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CALL runtime·memmove(SB)
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MOVD 64(RSP), R5
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MOVD 72(RSP), R6
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MOVD 80(RSP), R7
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MOVD 88(RSP), R8
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MOVD 96(RSP), R9
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MOVD 120(RSP), R15
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ADD $128, RSP, R17
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MOVW $0xa7bd, R16
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MOVKW $(0x1e35<<16), R16
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B inner1
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inlineEmitLiteralEnd:
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// End inline of the emitLiteral call.
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// ----------------------------------------
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emitLiteralFastPath:
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// !!! Emit the 1-byte encoding "uint8(len(lit)-1)<<2".
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MOVB R3, R4
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SUBW $1, R4, R4
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AND $0xff, R4, R4
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LSLW $2, R4, R4
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MOVB R4, (R8)
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ADD $1, R8, R8
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// !!! Implement the copy from lit to dst as a 16-byte load and store.
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// (Encode's documentation says that dst and src must not overlap.)
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//
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// This always copies 16 bytes, instead of only len(lit) bytes, but that's
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// OK. Subsequent iterations will fix up the overrun.
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//
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// Note that on arm64, it is legal and cheap to issue unaligned 8-byte or
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// 16-byte loads and stores. This technique probably wouldn't be as
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// effective on architectures that are fussier about alignment.
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LDP 0(R10), (R0, R1)
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STP (R0, R1), 0(R8)
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ADD R3, R8, R8
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inner1:
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// for { etc }
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// base := s
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MOVD R7, R12
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// !!! offset := base - candidate
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MOVD R12, R11
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SUB R15, R11, R11
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SUB R6, R11, R11
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// ----------------------------------------
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// Begin inline of the extendMatch call.
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//
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// s = extendMatch(src, candidate+4, s+4)
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// !!! R14 = &src[len(src)]
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MOVD src_len+32(FP), R14
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ADD R6, R14, R14
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// !!! R13 = &src[len(src) - 8]
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MOVD R14, R13
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SUB $8, R13, R13
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// !!! R15 = &src[candidate + 4]
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ADD $4, R15, R15
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ADD R6, R15, R15
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// !!! s += 4
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ADD $4, R7, R7
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inlineExtendMatchCmp8:
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// As long as we are 8 or more bytes before the end of src, we can load and
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// compare 8 bytes at a time. If those 8 bytes are equal, repeat.
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CMP R13, R7
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BHI inlineExtendMatchCmp1
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MOVD (R15), R3
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|
MOVD (R7), R4
|
|
CMP R4, R3
|
|
BNE inlineExtendMatchBSF
|
|
ADD $8, R15, R15
|
|
ADD $8, R7, R7
|
|
B inlineExtendMatchCmp8
|
|
|
|
inlineExtendMatchBSF:
|
|
// If those 8 bytes were not equal, XOR the two 8 byte values, and return
|
|
// the index of the first byte that differs.
|
|
// RBIT reverses the bit order, then CLZ counts the leading zeros, the
|
|
// combination of which finds the least significant bit which is set.
|
|
// The arm64 architecture is little-endian, and the shift by 3 converts
|
|
// a bit index to a byte index.
|
|
EOR R3, R4, R4
|
|
RBIT R4, R4
|
|
CLZ R4, R4
|
|
ADD R4>>3, R7, R7
|
|
B inlineExtendMatchEnd
|
|
|
|
inlineExtendMatchCmp1:
|
|
// In src's tail, compare 1 byte at a time.
|
|
CMP R7, R14
|
|
BLS inlineExtendMatchEnd
|
|
MOVB (R15), R3
|
|
MOVB (R7), R4
|
|
CMP R4, R3
|
|
BNE inlineExtendMatchEnd
|
|
ADD $1, R15, R15
|
|
ADD $1, R7, R7
|
|
B inlineExtendMatchCmp1
|
|
|
|
inlineExtendMatchEnd:
|
|
// End inline of the extendMatch call.
|
|
// ----------------------------------------
|
|
|
|
// ----------------------------------------
|
|
// Begin inline of the emitCopy call.
|
|
//
|
|
// d += emitCopy(dst[d:], base-candidate, s-base)
|
|
|
|
// !!! length := s - base
|
|
MOVD R7, R3
|
|
SUB R12, R3, R3
|
|
|
|
inlineEmitCopyLoop0:
|
|
// for length >= 68 { etc }
|
|
MOVW $68, R2
|
|
CMPW R2, R3
|
|
BLT inlineEmitCopyStep1
|
|
|
|
// Emit a length 64 copy, encoded as 3 bytes.
|
|
MOVD $0xfe, R1
|
|
MOVB R1, 0(R8)
|
|
MOVW R11, 1(R8)
|
|
ADD $3, R8, R8
|
|
SUBW $64, R3, R3
|
|
B inlineEmitCopyLoop0
|
|
|
|
inlineEmitCopyStep1:
|
|
// if length > 64 { etc }
|
|
MOVW $64, R2
|
|
CMPW R2, R3
|
|
BLE inlineEmitCopyStep2
|
|
|
|
// Emit a length 60 copy, encoded as 3 bytes.
|
|
MOVD $0xee, R1
|
|
MOVB R1, 0(R8)
|
|
MOVW R11, 1(R8)
|
|
ADD $3, R8, R8
|
|
SUBW $60, R3, R3
|
|
|
|
inlineEmitCopyStep2:
|
|
// if length >= 12 || offset >= 2048 { goto inlineEmitCopyStep3 }
|
|
MOVW $12, R2
|
|
CMPW R2, R3
|
|
BGE inlineEmitCopyStep3
|
|
MOVW $2048, R2
|
|
CMPW R2, R11
|
|
BGE inlineEmitCopyStep3
|
|
|
|
// Emit the remaining copy, encoded as 2 bytes.
|
|
MOVB R11, 1(R8)
|
|
LSRW $8, R11, R11
|
|
LSLW $5, R11, R11
|
|
SUBW $4, R3, R3
|
|
AND $0xff, R3, R3
|
|
LSLW $2, R3, R3
|
|
ORRW R3, R11, R11
|
|
ORRW $1, R11, R11
|
|
MOVB R11, 0(R8)
|
|
ADD $2, R8, R8
|
|
B inlineEmitCopyEnd
|
|
|
|
inlineEmitCopyStep3:
|
|
// Emit the remaining copy, encoded as 3 bytes.
|
|
SUBW $1, R3, R3
|
|
LSLW $2, R3, R3
|
|
ORRW $2, R3, R3
|
|
MOVB R3, 0(R8)
|
|
MOVW R11, 1(R8)
|
|
ADD $3, R8, R8
|
|
|
|
inlineEmitCopyEnd:
|
|
// End inline of the emitCopy call.
|
|
// ----------------------------------------
|
|
|
|
// nextEmit = s
|
|
MOVD R7, R10
|
|
|
|
// if s >= sLimit { goto emitRemainder }
|
|
MOVD R7, R3
|
|
SUB R6, R3, R3
|
|
CMP R3, R9
|
|
BLS emitRemainder
|
|
|
|
// As per the encode_other.go code:
|
|
//
|
|
// We could immediately etc.
|
|
|
|
// x := load64(src, s-1)
|
|
MOVD -1(R7), R14
|
|
|
|
// prevHash := hash(uint32(x>>0), shift)
|
|
MOVW R14, R11
|
|
MULW R16, R11, R11
|
|
LSRW R5, R11, R11
|
|
|
|
// table[prevHash] = uint16(s-1)
|
|
MOVD R7, R3
|
|
SUB R6, R3, R3
|
|
SUB $1, R3, R3
|
|
|
|
MOVHU R3, 0(R17)(R11<<1)
|
|
|
|
// currHash := hash(uint32(x>>8), shift)
|
|
LSR $8, R14, R14
|
|
MOVW R14, R11
|
|
MULW R16, R11, R11
|
|
LSRW R5, R11, R11
|
|
|
|
// candidate = int(table[currHash])
|
|
MOVHU 0(R17)(R11<<1), R15
|
|
|
|
// table[currHash] = uint16(s)
|
|
ADD $1, R3, R3
|
|
MOVHU R3, 0(R17)(R11<<1)
|
|
|
|
// if uint32(x>>8) == load32(src, candidate) { continue }
|
|
MOVW (R6)(R15), R4
|
|
CMPW R4, R14
|
|
BEQ inner1
|
|
|
|
// nextHash = hash(uint32(x>>16), shift)
|
|
LSR $8, R14, R14
|
|
MOVW R14, R11
|
|
MULW R16, R11, R11
|
|
LSRW R5, R11, R11
|
|
|
|
// s++
|
|
ADD $1, R7, R7
|
|
|
|
// break out of the inner1 for loop, i.e. continue the outer loop.
|
|
B outer
|
|
|
|
emitRemainder:
|
|
// if nextEmit < len(src) { etc }
|
|
MOVD src_len+32(FP), R3
|
|
ADD R6, R3, R3
|
|
CMP R3, R10
|
|
BEQ encodeBlockEnd
|
|
|
|
// d += emitLiteral(dst[d:], src[nextEmit:])
|
|
//
|
|
// Push args.
|
|
MOVD R8, 8(RSP)
|
|
MOVD $0, 16(RSP) // Unnecessary, as the callee ignores it, but conservative.
|
|
MOVD $0, 24(RSP) // Unnecessary, as the callee ignores it, but conservative.
|
|
MOVD R10, 32(RSP)
|
|
SUB R10, R3, R3
|
|
MOVD R3, 40(RSP)
|
|
MOVD R3, 48(RSP) // Unnecessary, as the callee ignores it, but conservative.
|
|
|
|
// Spill local variables (registers) onto the stack; call; unspill.
|
|
MOVD R8, 88(RSP)
|
|
CALL ·emitLiteral(SB)
|
|
MOVD 88(RSP), R8
|
|
|
|
// Finish the "d +=" part of "d += emitLiteral(etc)".
|
|
MOVD 56(RSP), R1
|
|
ADD R1, R8, R8
|
|
|
|
encodeBlockEnd:
|
|
MOVD dst_base+0(FP), R3
|
|
SUB R3, R8, R8
|
|
MOVD R8, d+48(FP)
|
|
RET
|