• Keith Randall's avatar
    cmd/compile,math: improve code generation for math.Abs · fb05948d
    Keith Randall authored
    Implement int reg <-> fp reg moves on amd64.
    If we see a load to int reg followed by an int->fp move, then we can just
    load to the fp reg instead.  Same for stores.
    
    math.Abs is now:
    
    MOVQ	"".x+8(SP), AX
    SHLQ	$1, AX
    SHRQ	$1, AX
    MOVQ	AX, "".~r1+16(SP)
    
    math.Copysign is now:
    
    MOVQ	"".x+8(SP), AX
    SHLQ	$1, AX
    SHRQ	$1, AX
    MOVQ	"".y+16(SP), CX
    SHRQ	$63, CX
    SHLQ	$63, CX
    ORQ	CX, AX
    MOVQ	AX, "".~r2+24(SP)
    
    math.Float64bits is now:
    
    MOVSD	"".x+8(SP), X0
    MOVSD	X0, "".~r1+16(SP)
    (it would be nicer to use a non-SSE reg for this, nothing is perfect)
    
    And due to the fix for #21440, the inlined version of these improve as well.
    
    name      old time/op  new time/op  delta
    Abs       1.38ns ± 5%  0.89ns ±10%  -35.54%  (p=0.000 n=10+10)
    Copysign  1.56ns ± 7%  1.35ns ± 6%  -13.77%  (p=0.000 n=9+10)
    
    Fixes #13095
    
    Change-Id: Ibd7f2792412a6668608780b0688a77062e1f1499
    Reviewed-on: https://go-review.googlesource.com/58732
    Run-TryBot: Keith Randall <khr@golang.org>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    Reviewed-by: 's avatarCherry Zhang <cherryyz@google.com>
    Reviewed-by: 's avatarIlya Tocar <ilya.tocar@intel.com>
    fb05948d
AMD64Ops.go 47.2 KB