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730 lines
16 KiB
730 lines
16 KiB
// Copyright 2016 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 XXX lines assemble on Go 1.4, 1.5 and 1.7, but not 1.6, due to a
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// Go toolchain regression. See https://github.com/golang/go/issues/15426 and
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// https://github.com/golang/snappy/issues/29
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//
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// As a workaround, the package was built with a known good assembler, and
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// those instructions were disassembled by "objdump -d" to yield the
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// 4e 0f b7 7c 5c 78 movzwq 0x78(%rsp,%r11,2),%r15
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// style comments, in AT&T asm syntax. Note that rsp here is a physical
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// register, not Go/asm's SP pseudo-register (see https://golang.org/doc/asm).
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// The instructions were then encoded as "BYTE $0x.." sequences, which assemble
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// fine on Go 1.6.
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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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// - AX len(lit)
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// - BX n
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// - DX return value
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// - DI &dst[i]
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// - R10 &lit[0]
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//
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// The 24 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, $24-56
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MOVQ dst_base+0(FP), DI
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MOVQ lit_base+24(FP), R10
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MOVQ lit_len+32(FP), AX
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MOVQ AX, DX
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MOVL AX, BX
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SUBL $1, BX
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CMPL BX, $60
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JLT oneByte
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CMPL BX, $256
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JLT twoBytes
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threeBytes:
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MOVB $0xf4, 0(DI)
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MOVW BX, 1(DI)
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ADDQ $3, DI
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ADDQ $3, DX
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JMP memmove
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twoBytes:
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MOVB $0xf0, 0(DI)
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MOVB BX, 1(DI)
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ADDQ $2, DI
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ADDQ $2, DX
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JMP memmove
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oneByte:
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SHLB $2, BX
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MOVB BX, 0(DI)
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ADDQ $1, DI
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ADDQ $1, DX
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memmove:
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MOVQ DX, 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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// DI, R10 and AX as arguments.
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MOVQ DI, 0(SP)
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MOVQ R10, 8(SP)
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MOVQ AX, 16(SP)
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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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// - AX length
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// - SI &dst[0]
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// - DI &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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MOVQ dst_base+0(FP), DI
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MOVQ DI, SI
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MOVQ offset+24(FP), R11
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MOVQ length+32(FP), AX
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loop0:
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// for length >= 68 { etc }
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CMPL AX, $68
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JLT step1
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// Emit a length 64 copy, encoded as 3 bytes.
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MOVB $0xfe, 0(DI)
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MOVW R11, 1(DI)
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ADDQ $3, DI
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SUBL $64, AX
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JMP loop0
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step1:
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// if length > 64 { etc }
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CMPL AX, $64
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JLE step2
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// Emit a length 60 copy, encoded as 3 bytes.
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MOVB $0xee, 0(DI)
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MOVW R11, 1(DI)
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ADDQ $3, DI
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SUBL $60, AX
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step2:
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// if length >= 12 || offset >= 2048 { goto step3 }
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CMPL AX, $12
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JGE step3
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CMPL R11, $2048
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JGE step3
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// Emit the remaining copy, encoded as 2 bytes.
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MOVB R11, 1(DI)
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SHRL $8, R11
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SHLB $5, R11
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SUBB $4, AX
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SHLB $2, AX
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ORB AX, R11
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ORB $1, R11
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MOVB R11, 0(DI)
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ADDQ $2, DI
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// Return the number of bytes written.
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SUBQ SI, DI
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MOVQ DI, 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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SUBL $1, AX
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SHLB $2, AX
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ORB $2, AX
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MOVB AX, 0(DI)
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MOVW R11, 1(DI)
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ADDQ $3, DI
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// Return the number of bytes written.
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SUBQ SI, DI
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MOVQ DI, 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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// - DX &src[0]
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// - SI &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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MOVQ src_base+0(FP), DX
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MOVQ src_len+8(FP), R14
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MOVQ i+24(FP), R15
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MOVQ j+32(FP), SI
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ADDQ DX, R14
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ADDQ DX, R15
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ADDQ DX, SI
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MOVQ R14, R13
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SUBQ $8, 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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CMPQ SI, R13
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JA cmp1
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MOVQ (R15), AX
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MOVQ (SI), BX
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CMPQ AX, BX
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JNE bsf
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ADDQ $8, R15
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ADDQ $8, SI
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JMP 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. The BSF instruction finds the
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// least significant 1 bit, the amd64 architecture is little-endian, and
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// the shift by 3 converts a bit index to a byte index.
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XORQ AX, BX
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BSFQ BX, BX
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SHRQ $3, BX
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ADDQ BX, SI
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// Convert from &src[ret] to ret.
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SUBQ DX, SI
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MOVQ SI, 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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CMPQ SI, R14
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JAE extendMatchEnd
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MOVB (R15), AX
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MOVB (SI), BX
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CMPB AX, BX
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JNE extendMatchEnd
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ADDQ $1, R15
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ADDQ $1, SI
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JMP cmp1
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extendMatchEnd:
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// Convert from &src[ret] to ret.
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SUBQ DX, SI
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MOVQ SI, 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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// - AX . .
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// - BX . .
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// - CX 56 shift (note that amd64 shifts by non-immediates must use CX).
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// - DX 64 &src[0], tableSize
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// - SI 72 &src[s]
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// - DI 80 &dst[d]
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// - R9 88 sLimit
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// - R10 . &src[nextEmit]
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// - R11 96 prevHash, currHash, nextHash, offset
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// - R12 104 &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 112 candidate
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//
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// The second column (56, 64, 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 56 bytes, to call other functions, and an extra 64 bytes, to spill
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// local variables (registers) during calls gives 32768 + 56 + 64 = 32888.
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TEXT ·encodeBlock(SB), 0, $32888-56
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MOVQ dst_base+0(FP), DI
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MOVQ src_base+24(FP), SI
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MOVQ src_len+32(FP), R14
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// shift, tableSize := uint32(32-8), 1<<8
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MOVQ $24, CX
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MOVQ $256, DX
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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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CMPQ DX, $16384
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JGE varTable
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CMPQ DX, R14
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JGE varTable
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SUBQ $1, CX
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SHLQ $1, DX
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JMP 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 MOVOU
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// writes 16 bytes, so we can do only tableSize/8 writes instead of the
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// 2048 writes that would zero-initialize all of table's 32768 bytes.
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SHRQ $3, DX
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LEAQ table-32768(SP), BX
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PXOR X0, X0
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memclr:
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MOVOU X0, 0(BX)
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ADDQ $16, BX
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SUBQ $1, DX
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JNZ memclr
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// !!! DX = &src[0]
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MOVQ SI, DX
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// sLimit := len(src) - inputMargin
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MOVQ R14, R9
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SUBQ $15, R9
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// !!! Pre-emptively spill CX, DX and R9 to the stack. Their values don't
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// change for the rest of the function.
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MOVQ CX, 56(SP)
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MOVQ DX, 64(SP)
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MOVQ R9, 88(SP)
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// nextEmit := 0
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MOVQ DX, R10
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// s := 1
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ADDQ $1, SI
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// nextHash := hash(load32(src, s), shift)
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MOVL 0(SI), R11
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IMULL $0x1e35a7bd, R11
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SHRL CX, R11
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outer:
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// for { etc }
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// skip := 32
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MOVQ $32, R12
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// nextS := s
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MOVQ SI, R13
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// candidate := 0
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MOVQ $0, R15
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inner0:
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// for { etc }
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// s := nextS
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MOVQ R13, SI
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// bytesBetweenHashLookups := skip >> 5
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MOVQ R12, R14
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SHRQ $5, R14
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// nextS = s + bytesBetweenHashLookups
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ADDQ R14, R13
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// skip += bytesBetweenHashLookups
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ADDQ R14, R12
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// if nextS > sLimit { goto emitRemainder }
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MOVQ R13, AX
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SUBQ DX, AX
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CMPQ AX, R9
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JA emitRemainder
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// candidate = int(table[nextHash])
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// XXX: MOVWQZX table-32768(SP)(R11*2), R15
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// XXX: 4e 0f b7 7c 5c 78 movzwq 0x78(%rsp,%r11,2),%r15
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BYTE $0x4e
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BYTE $0x0f
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BYTE $0xb7
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BYTE $0x7c
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BYTE $0x5c
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BYTE $0x78
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// table[nextHash] = uint16(s)
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MOVQ SI, AX
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SUBQ DX, AX
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// XXX: MOVW AX, table-32768(SP)(R11*2)
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// XXX: 66 42 89 44 5c 78 mov %ax,0x78(%rsp,%r11,2)
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BYTE $0x66
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BYTE $0x42
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BYTE $0x89
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BYTE $0x44
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BYTE $0x5c
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BYTE $0x78
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// nextHash = hash(load32(src, nextS), shift)
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MOVL 0(R13), R11
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IMULL $0x1e35a7bd, R11
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SHRL CX, R11
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// if load32(src, s) != load32(src, candidate) { continue } break
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MOVL 0(SI), AX
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MOVL (DX)(R15*1), BX
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CMPL AX, BX
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JNE 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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MOVQ SI, AX
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SUBQ R10, AX
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CMPQ AX, $16
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JLE 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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MOVL AX, BX
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SUBL $1, BX
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CMPL BX, $60
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JLT inlineEmitLiteralOneByte
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CMPL BX, $256
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JLT inlineEmitLiteralTwoBytes
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inlineEmitLiteralThreeBytes:
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MOVB $0xf4, 0(DI)
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MOVW BX, 1(DI)
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ADDQ $3, DI
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JMP inlineEmitLiteralMemmove
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inlineEmitLiteralTwoBytes:
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MOVB $0xf0, 0(DI)
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MOVB BX, 1(DI)
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ADDQ $2, DI
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JMP inlineEmitLiteralMemmove
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inlineEmitLiteralOneByte:
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SHLB $2, BX
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MOVB BX, 0(DI)
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ADDQ $1, DI
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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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// DI, R10 and AX as arguments.
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MOVQ DI, 0(SP)
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MOVQ R10, 8(SP)
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MOVQ AX, 16(SP)
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ADDQ AX, DI // Finish the "d +=" part of "d += emitLiteral(etc)".
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MOVQ SI, 72(SP)
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MOVQ DI, 80(SP)
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MOVQ R15, 112(SP)
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CALL runtime·memmove(SB)
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MOVQ 56(SP), CX
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MOVQ 64(SP), DX
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MOVQ 72(SP), SI
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MOVQ 80(SP), DI
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MOVQ 88(SP), R9
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MOVQ 112(SP), R15
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JMP 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 AX, BX
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SUBB $1, BX
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SHLB $2, BX
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MOVB BX, (DI)
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ADDQ $1, DI
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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 amd64, 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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MOVOU 0(R10), X0
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MOVOU X0, 0(DI)
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ADDQ AX, DI
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inner1:
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// for { etc }
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// base := s
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MOVQ SI, R12
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// !!! offset := base - candidate
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MOVQ R12, R11
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SUBQ R15, R11
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SUBQ DX, 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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MOVQ src_len+32(FP), R14
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ADDQ DX, R14
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// !!! R13 = &src[len(src) - 8]
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MOVQ R14, R13
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SUBQ $8, R13
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// !!! R15 = &src[candidate + 4]
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ADDQ $4, R15
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ADDQ DX, R15
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// !!! s += 4
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ADDQ $4, SI
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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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CMPQ SI, R13
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JA inlineExtendMatchCmp1
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MOVQ (R15), AX
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MOVQ (SI), BX
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CMPQ AX, BX
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JNE inlineExtendMatchBSF
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ADDQ $8, R15
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ADDQ $8, SI
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JMP inlineExtendMatchCmp8
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inlineExtendMatchBSF:
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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. The BSF instruction finds the
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// least significant 1 bit, the amd64 architecture is little-endian, and
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// the shift by 3 converts a bit index to a byte index.
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XORQ AX, BX
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BSFQ BX, BX
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SHRQ $3, BX
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ADDQ BX, SI
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JMP inlineExtendMatchEnd
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|
|
inlineExtendMatchCmp1:
|
|
// In src's tail, compare 1 byte at a time.
|
|
CMPQ SI, R14
|
|
JAE inlineExtendMatchEnd
|
|
MOVB (R15), AX
|
|
MOVB (SI), BX
|
|
CMPB AX, BX
|
|
JNE inlineExtendMatchEnd
|
|
ADDQ $1, R15
|
|
ADDQ $1, SI
|
|
JMP 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
|
|
MOVQ SI, AX
|
|
SUBQ R12, AX
|
|
|
|
inlineEmitCopyLoop0:
|
|
// for length >= 68 { etc }
|
|
CMPL AX, $68
|
|
JLT inlineEmitCopyStep1
|
|
|
|
// Emit a length 64 copy, encoded as 3 bytes.
|
|
MOVB $0xfe, 0(DI)
|
|
MOVW R11, 1(DI)
|
|
ADDQ $3, DI
|
|
SUBL $64, AX
|
|
JMP inlineEmitCopyLoop0
|
|
|
|
inlineEmitCopyStep1:
|
|
// if length > 64 { etc }
|
|
CMPL AX, $64
|
|
JLE inlineEmitCopyStep2
|
|
|
|
// Emit a length 60 copy, encoded as 3 bytes.
|
|
MOVB $0xee, 0(DI)
|
|
MOVW R11, 1(DI)
|
|
ADDQ $3, DI
|
|
SUBL $60, AX
|
|
|
|
inlineEmitCopyStep2:
|
|
// if length >= 12 || offset >= 2048 { goto inlineEmitCopyStep3 }
|
|
CMPL AX, $12
|
|
JGE inlineEmitCopyStep3
|
|
CMPL R11, $2048
|
|
JGE inlineEmitCopyStep3
|
|
|
|
// Emit the remaining copy, encoded as 2 bytes.
|
|
MOVB R11, 1(DI)
|
|
SHRL $8, R11
|
|
SHLB $5, R11
|
|
SUBB $4, AX
|
|
SHLB $2, AX
|
|
ORB AX, R11
|
|
ORB $1, R11
|
|
MOVB R11, 0(DI)
|
|
ADDQ $2, DI
|
|
JMP inlineEmitCopyEnd
|
|
|
|
inlineEmitCopyStep3:
|
|
// Emit the remaining copy, encoded as 3 bytes.
|
|
SUBL $1, AX
|
|
SHLB $2, AX
|
|
ORB $2, AX
|
|
MOVB AX, 0(DI)
|
|
MOVW R11, 1(DI)
|
|
ADDQ $3, DI
|
|
|
|
inlineEmitCopyEnd:
|
|
// End inline of the emitCopy call.
|
|
// ----------------------------------------
|
|
|
|
// nextEmit = s
|
|
MOVQ SI, R10
|
|
|
|
// if s >= sLimit { goto emitRemainder }
|
|
MOVQ SI, AX
|
|
SUBQ DX, AX
|
|
CMPQ AX, R9
|
|
JAE emitRemainder
|
|
|
|
// As per the encode_other.go code:
|
|
//
|
|
// We could immediately etc.
|
|
|
|
// x := load64(src, s-1)
|
|
MOVQ -1(SI), R14
|
|
|
|
// prevHash := hash(uint32(x>>0), shift)
|
|
MOVL R14, R11
|
|
IMULL $0x1e35a7bd, R11
|
|
SHRL CX, R11
|
|
|
|
// table[prevHash] = uint16(s-1)
|
|
MOVQ SI, AX
|
|
SUBQ DX, AX
|
|
SUBQ $1, AX
|
|
|
|
// XXX: MOVW AX, table-32768(SP)(R11*2)
|
|
// XXX: 66 42 89 44 5c 78 mov %ax,0x78(%rsp,%r11,2)
|
|
BYTE $0x66
|
|
BYTE $0x42
|
|
BYTE $0x89
|
|
BYTE $0x44
|
|
BYTE $0x5c
|
|
BYTE $0x78
|
|
|
|
// currHash := hash(uint32(x>>8), shift)
|
|
SHRQ $8, R14
|
|
MOVL R14, R11
|
|
IMULL $0x1e35a7bd, R11
|
|
SHRL CX, R11
|
|
|
|
// candidate = int(table[currHash])
|
|
// XXX: MOVWQZX table-32768(SP)(R11*2), R15
|
|
// XXX: 4e 0f b7 7c 5c 78 movzwq 0x78(%rsp,%r11,2),%r15
|
|
BYTE $0x4e
|
|
BYTE $0x0f
|
|
BYTE $0xb7
|
|
BYTE $0x7c
|
|
BYTE $0x5c
|
|
BYTE $0x78
|
|
|
|
// table[currHash] = uint16(s)
|
|
ADDQ $1, AX
|
|
|
|
// XXX: MOVW AX, table-32768(SP)(R11*2)
|
|
// XXX: 66 42 89 44 5c 78 mov %ax,0x78(%rsp,%r11,2)
|
|
BYTE $0x66
|
|
BYTE $0x42
|
|
BYTE $0x89
|
|
BYTE $0x44
|
|
BYTE $0x5c
|
|
BYTE $0x78
|
|
|
|
// if uint32(x>>8) == load32(src, candidate) { continue }
|
|
MOVL (DX)(R15*1), BX
|
|
CMPL R14, BX
|
|
JEQ inner1
|
|
|
|
// nextHash = hash(uint32(x>>16), shift)
|
|
SHRQ $8, R14
|
|
MOVL R14, R11
|
|
IMULL $0x1e35a7bd, R11
|
|
SHRL CX, R11
|
|
|
|
// s++
|
|
ADDQ $1, SI
|
|
|
|
// break out of the inner1 for loop, i.e. continue the outer loop.
|
|
JMP outer
|
|
|
|
emitRemainder:
|
|
// if nextEmit < len(src) { etc }
|
|
MOVQ src_len+32(FP), AX
|
|
ADDQ DX, AX
|
|
CMPQ R10, AX
|
|
JEQ encodeBlockEnd
|
|
|
|
// d += emitLiteral(dst[d:], src[nextEmit:])
|
|
//
|
|
// Push args.
|
|
MOVQ DI, 0(SP)
|
|
MOVQ $0, 8(SP) // Unnecessary, as the callee ignores it, but conservative.
|
|
MOVQ $0, 16(SP) // Unnecessary, as the callee ignores it, but conservative.
|
|
MOVQ R10, 24(SP)
|
|
SUBQ R10, AX
|
|
MOVQ AX, 32(SP)
|
|
MOVQ AX, 40(SP) // Unnecessary, as the callee ignores it, but conservative.
|
|
|
|
// Spill local variables (registers) onto the stack; call; unspill.
|
|
MOVQ DI, 80(SP)
|
|
CALL ·emitLiteral(SB)
|
|
MOVQ 80(SP), DI
|
|
|
|
// Finish the "d +=" part of "d += emitLiteral(etc)".
|
|
ADDQ 48(SP), DI
|
|
|
|
encodeBlockEnd:
|
|
MOVQ dst_base+0(FP), AX
|
|
SUBQ AX, DI
|
|
MOVQ DI, d+48(FP)
|
|
RET
|
|
|