4 void daxpy(size_t n, double a, const double x[], double y[])
6 for (size_t i = 0; i < n; i++) {
12 # SVP64 Power ISA version
14 Summary: 9 instructions (see below, 8 instructions) 5 of which are 64-bit
15 for a total of 14 "words".
22 1 mtctr 5 # move n to CTR
23 2 addi r10,r6,0 # copy y-ptr into r10 (y')
25 4 setvl MAXVL=32,VL=CTR # actually VL=MIN(MAXVL,CTR)
26 5 sv.lfdup *32,8(6) # load x into fp32-63, inc x
27 6 sv.lfdup *64,8(7) # load y into fp64-95, inc y
28 7 sv.fmadd *64,*64,1,*32 # (*y) = (*y) * (*x) + fp1
29 8 sv.stfdup *64,8(10) # store at y-copy, inc y'
30 9 sv.bc/ctr .L2 # decrement CTR by VL
34 A refinement, reducing 1 instruction and register port usage.
35 Relies on post-increment, relies on no overlap between x and y
36 in memory, and critically relies on y overwrite.
43 1 mtctr 5 # move n to CTR
45 3 setvl MAXVL=32,VL=CTR # actually VL=MIN(MAXVL,CTR)
46 4 sv.lfdup *32,8(6) # load x into fp32-63, incr x
47 5 sv.lfd *64,8(7) # load y into fp64-95, NO INC
48 6 sv.fmadd *64,*64,1,*32 # (*y) = (*y) * (*x) + fp1
49 7 sv.stfdup *64,8(7) # store at y, incr y
50 8 sv.bc/ctr .L2 # decrement CTR by VL
56 Summary: 12 instructions, 7 32-bit and 5 16-bit for a total of 9.5 "words"
59 # a0 is n, a1 is pointer to x[0], a2 is pointer to y[0], fa0 is a
61 vsetdcfg t0 # enable 2 64b Fl.Pt. registers
63 setvl t0, a0 # vl = t0 = min(mvl, n)
64 vld v0, a1 # load vector x
65 c.slli t1, t0, 3 # t1 = vl * 8 (in bytes)
66 vld v1, a2 # load vector y
67 c.add a1, a1, t1 # increment pointer to x by vl*8
68 vfmadd v1, v0, fa0, v1 # v1 += v0 * fa0 (y = a * x + y)
69 c.sub a0, a0, t0 # n -= vl (t0)
71 c.add a2, a2, t1 # increment pointer to y by vl*8
72 c.bnez a0, loop # repeat if n != 0
79 1 // x0 = &x[0], x1 = &y[0], x2 = &a, x3 = &n
81 3 ldrswx3, [x3] // x3=*n
83 5 whilelt p0.d, x4, x3 // p0=while(i++<n)
84 6 ld1rdz0.d, p0/z, [x2] // p0:z0=bcast(*a)
86 8 ld1d z1.d, p0/z, [x0, x4, lsl #3] // p0:z1=x[i]
87 9 ld1d z2.d, p0/z, [x1, x4, lsl #3] // p0:z2=y[i]
88 10 fmla z2.d, p0/m, z1.d, z0.d // p0?z2+=x[i]*a
89 11 st1d z2.d, p0, [x1, x4, lsl #3] // p0?y[i]=z2
90 12 incd x4 // i+=(VL/64)
92 14 whilelt p0.d, x4, x3 // p0=while(i++<n)
93 15 b.first .loop // more to do?