• Ilya Tocar's avatar
    cmd/compile/internal/ssa: use sse to zero on amd64 · df709828
    Ilya Tocar authored
    Use 16-byte stores instead of 8-byte stores to zero small blocks.
    Also switch to duffzero for 65+ bytes only, because for each
    duffzero call we also save/restore BP, so call requires 4 instructions
    and replacing it with 4 sse stores doesn't cause code-bloat.
    Also switch duffzero to use leaq, instead of addq to avoid clobbering flags.
    
    ClearFat8-6     0.54ns ± 0%  0.54ns ± 0%     ~     (all equal)
    ClearFat12-6    1.07ns ± 0%  1.07ns ± 0%     ~     (all equal)
    ClearFat16-6    1.07ns ± 0%  0.69ns ± 0%  -35.51%  (p=0.001 n=8+9)
    ClearFat24-6    1.61ns ± 1%  1.07ns ± 0%  -33.33%  (p=0.000 n=10+10)
    ClearFat32-6    2.14ns ± 0%  1.07ns ± 0%  -50.00%  (p=0.001 n=8+9)
    ClearFat40-6    2.67ns ± 1%  1.61ns ± 0%  -39.72%  (p=0.000 n=10+8)
    ClearFat48-6    3.75ns ± 0%  2.68ns ± 0%  -28.59%  (p=0.000 n=9+9)
    ClearFat56-6    4.29ns ± 0%  3.22ns ± 0%  -25.10%  (p=0.000 n=9+9)
    ClearFat64-6    4.30ns ± 0%  3.22ns ± 0%  -25.15%  (p=0.000 n=8+8)
    ClearFat128-6   7.50ns ± 1%  7.51ns ± 0%     ~     (p=0.767 n=10+9)
    ClearFat256-6   13.9ns ± 1%  13.9ns ± 1%     ~     (p=0.257 n=10+10)
    ClearFat512-6   26.8ns ± 0%  26.8ns ± 0%     ~     (p=0.467 n=8+8)
    ClearFat1024-6  52.5ns ± 0%  52.5ns ± 0%     ~     (p=1.000 n=8+8)
    
    Also shaves ~20kb from go tool:
    
    go_old 10384994
    go_new 10364514 [-20480 bytes]
    
    section differences
    global text (code) = -20585 bytes (-0.532047%)
    read-only data = -302 bytes (-0.018101%)
    Total difference -20887 bytes (-0.348731%)
    
    Change-Id: I15854e87544545c1af24775df895e38e16e12694
    Reviewed-on: https://go-review.googlesource.com/54410
    Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    Reviewed-by: 's avatarKeith Randall <khr@golang.org>
    df709828
ggen.go 4.49 KB