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decompress_amd64.s.in
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decompress_amd64.s.in
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// +build !appengine
// +build gc
// +build !noasm
#include "textflag.h"
#include "funcdata.h"
#include "go_asm.h"
#define bufoff 256 // see decompress.go, we're using [4][256]byte table
//func decompress4x_main_loop_x86(pbr0, pbr1, pbr2, pbr3 *bitReaderShifted,
// peekBits uint8, buf *byte, tbl *dEntrySingle) (int, bool)
TEXT ·decompress4x_main_loop_x86(SB), NOSPLIT, $8
#define off R8
#define buffer DI
#define table SI
#define br_bits_read R9
#define br_value R10
#define br_offset R11
#define peek_bits R12
#define exhausted DX
#define br0 R13
#define br1 R14
#define br2 R15
#define br3 BP
MOVQ BP, 0(SP)
XORQ exhausted, exhausted // exhausted = false
XORQ off, off // off = 0
MOVBQZX peekBits+32(FP), peek_bits
MOVQ buf+40(FP), buffer
MOVQ tbl+48(FP), table
MOVQ pbr0+0(FP), br0
MOVQ pbr1+8(FP), br1
MOVQ pbr2+16(FP), br2
MOVQ pbr3+24(FP), br3
main_loop:
{{ define "decode_2_values_x86" }}
// const stream = {{ var "id" }}
// br{{ var "id"}}.fillFast()
MOVBQZX bitReaderShifted_bitsRead(br{{ var "id" }}), br_bits_read
MOVQ bitReaderShifted_value(br{{ var "id" }}), br_value
MOVQ bitReaderShifted_off(br{{ var "id" }}), br_offset
// if b.bitsRead >= 32 {
CMPQ br_bits_read, $32
JB skip_fill{{ var "id" }}
SUBQ $32, br_bits_read // b.bitsRead -= 32
SUBQ $4, br_offset // b.off -= 4
// v := b.in[b.off-4 : b.off]
// v = v[:4]
// low := (uint32(v[0])) | (uint32(v[1]) << 8) | (uint32(v[2]) << 16) | (uint32(v[3]) << 24)
MOVQ bitReaderShifted_in(br{{ var "id" }}), AX
MOVL 0(br_offset)(AX*1), AX // AX = uint32(b.in[b.off:b.off+4])
// b.value |= uint64(low) << (b.bitsRead & 63)
MOVQ br_bits_read, CX
SHLQ CL, AX
ORQ AX, br_value
// exhausted = exhausted || (br{{ var "id"}}.off < 4)
CMPQ br_offset, $4
SETLT DL
ORB DL, DH
// }
skip_fill{{ var "id" }}:
// val0 := br{{ var "id"}}.peekTopBits(peekBits)
MOVQ br_value, AX
MOVQ peek_bits, CX
SHRQ CL, AX // AX = (value >> peek_bits) & mask
// v0 := table[val0&mask]
MOVW 0(table)(AX*2), AX // AX - v0
// br{{ var "id"}}.advance(uint8(v0.entry))
MOVB AH, BL // BL = uint8(v0.entry >> 8)
MOVBQZX AL, CX
SHLQ CL, br_value // value <<= n
ADDQ CX, br_bits_read // bits_read += n
// val1 := br{{ var "id"}}.peekTopBits(peekBits)
MOVQ peek_bits, CX
MOVQ br_value, AX
SHRQ CL, AX // AX = (value >> peek_bits) & mask
// v1 := table[val1&mask]
MOVW 0(table)(AX*2), AX // AX - v1
// br{{ var "id"}}.advance(uint8(v1.entry))
MOVB AH, BH // BH = uint8(v1.entry >> 8)
MOVBQZX AL, CX
SHLQ CX, br_value // value <<= n
ADDQ CX, br_bits_read // bits_read += n
// these two writes get coalesced
// buf[stream][off] = uint8(v0.entry >> 8)
// buf[stream][off+1] = uint8(v1.entry >> 8)
MOVW BX, {{ var "bufofs" }}(buffer)(off*1)
// update the bitrader reader structure
MOVB br_bits_read, bitReaderShifted_bitsRead(br{{ var "id" }})
MOVQ br_value, bitReaderShifted_value(br{{ var "id" }})
MOVQ br_offset, bitReaderShifted_off(br{{ var "id" }})
{{ end }}
{{ set "id" "0" }}
{{ set "ofs" "0" }}
{{ set "bufofs" "0" }} {{/* id * bufoff */}}
{{ template "decode_2_values_x86" . }}
{{ set "id" "1" }}
{{ set "ofs" "8" }}
{{ set "bufofs" "256" }}
{{ template "decode_2_values_x86" . }}
{{ set "id" "2" }}
{{ set "ofs" "16" }}
{{ set "bufofs" "512" }}
{{ template "decode_2_values_x86" . }}
{{ set "id" "3" }}
{{ set "ofs" "24" }}
{{ set "bufofs" "768" }}
{{ template "decode_2_values_x86" . }}
ADDQ $2, off // off += 2
TESTB DH, DH // any br[i].ofs < 4?
JNZ end
CMPQ off, $bufoff
JL main_loop
end:
MOVQ 0(SP), BP
MOVB off, ret+56(FP)
RET
#undef off
#undef buffer
#undef table
#undef br_bits_read
#undef br_value
#undef br_offset
#undef peek_bits
#undef exhausted
#undef br0
#undef br1
#undef br2
#undef br3