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// +build sse
// +build amd64
#include "textflag.h"
// func mulAsm(a, b []float64)
TEXT ·mulAsm(SB), NOSPLIT, $0
MOVQ a_data+0(FP), SI
MOVQ b_data+24(FP), DI // use destination index register for this
MOVQ a_len+8(FP), AX // len(a) into AX
// check if there are at least 8 elements
SUBQ $8, AX
JL remainder
loop:
// a[0]
MOVAPD (SI), X0
MOVAPD (DI), X1
MULPD X0, X1
MOVAPD X1, (SI)
MOVAPD 16(SI), X2
MOVAPD 16(DI), X3
MULPD X2, X3
MOVAPD X3, 16(SI)
MOVAPD 32(SI), X4
MOVAPD 32(DI), X5
MULPD X4, X5
MOVAPD X5, 32(SI)
MOVAPD 48(SI), X6
MOVAPD 48(DI), X7
MULPD X6, X7
MOVAPD X7, 48(SI)
// update pointers. 4 registers, 2 elements at once, each element is 8 bytes
ADDQ $64, SI
ADDQ $64, DI
// len(a) is now 4*2 elements less
SUBQ $8, AX
JGE loop
remainder:
ADDQ $8, AX
JE done
remainderloop:
MOVSD (SI), X0
MOVSD (DI), X1
MULSD X0, X1
MOVSD X1, (SI)
// update pointer to the top of the data
ADDQ $8, SI
ADDQ $8, DI
DECQ AX
JNE remainderloop
done:
RET
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