zstd: extend executeSimple with history support #542
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"Regressions" seems within margin of error. Good job, I will go through it. |
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Impact of commit 3a35124 (comparison with the previous commit from this branch). Can't tell it's significantly better or worse, except few cases. |
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So a tricky situation is that we cannot overread from history, since we may get out of the current page. So we need a "precise" memory copier. I have one for s2 which can be adapted. It is used for sizes 1->64, but it could be 0 -> 16 so it can be called whenever there is less than 16 bytes left. Untested, but this should be something like it: // func genMemMoveShort
// src and dst may not overlap.
// No registers are updated.
// Length must be 0 -> 16 bytes
func genMemMoveShort(name string, dst, src, length reg.GPVirtual, end LabelRef) {
Comment("genMemMoveShort")
AX, CX := GP64(), GP64()
name += "_memmove_"
// Only enable if length can be 0.
if true {
TESTQ(length, length)
JEQ(end)
}
CMPQ(length, U8(3))
JB(LabelRef(name + "move_1or2"))
JE(LabelRef(name + "move_3"))
CMPQ(length, U8(8))
JB(LabelRef(name + "move_4through7"))
//Label(name + "move_8through16")
MOVQ(Mem{Base: src}, AX)
MOVQ(Mem{Base: src, Disp: -8, Index: length, Scale: 1}, CX)
MOVQ(AX, Mem{Base: dst})
MOVQ(CX, Mem{Base: dst, Disp: -8, Index: length, Scale: 1})
JMP(end)
Label(name + "move_1or2")
MOVB(Mem{Base: src}, AX.As8())
MOVB(Mem{Base: src, Disp: -1, Index: length, Scale: 1}, CX.As8())
MOVB(AX.As8(), Mem{Base: dst})
MOVB(CX.As8(), Mem{Base: dst, Disp: -1, Index: length, Scale: 1})
JMP(end)
Label(name + "move_3")
MOVW(Mem{Base: src}, AX.As16())
MOVB(Mem{Base: src, Disp: 2}, CX.As8())
MOVW(AX.As16(), Mem{Base: dst})
MOVB(CX.As8(), Mem{Base: dst, Disp: 2})
JMP(end)
Label(name + "move_4through7")
MOVL(Mem{Base: src}, AX.As32())
MOVL(Mem{Base: src, Disp: -4, Index: length, Scale: 1}, CX.As32())
MOVL(AX.As32(), Mem{Base: dst})
MOVL(CX.As32(), Mem{Base: dst, Disp: -4, Index: length, Scale: 1})
JMP(end)
} |
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Right, I will change it. |
WojciechMula
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OK, I used another memory copy routine for history. Updated the main issue with current timings. Still nice improvements for cases with history. |
klauspost
requested changes
Apr 4, 2022
Co-authored-by: Klaus Post <klauspost@gmail.com>
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Add history support in the asm implementation. Part of task #515.
As usual marking as a draft, because of few failing tests.[fixed]Performance comparison between the current master and this branch on an IceLake machine with the hacked
decodeSyncis below. There are some nice speedups, but there are also regressions for almost all cases without history. To overcome that, we can have two specialisations:executeWithoutDictionaryandexecuteWithoutDictionatyAndHistory- what do you think?