4ncopy.ys

#/* $begin ncopy-ys */
##################################################################
# ncopy.ys - Copy a src block of len words to dst.
# Return the number of positive words (>0) contained in src.
#
# Include your name and ID here.
#
# Describe how and why you modified the baseline code.
# 1. use iaddq.
# 2. unroll loop.
##################################################################
# Do not modify this portion
# Function prologue.
# %rdi = src, %rsi = dst, %rdx = len
ncopy:

##################################################################
# You can modify this portion
	# Loop header
	xorq %rax,%rax		# count = 0;
        rrmovq %rdx, %rcx
        iaddq $-8, %rcx 
	#andq %rdx,%rdx		# len <= 0?
	jle Next
Next:   rrmovq %rdx, %rcx
        iaddq $-4, %rcx
        jle Next2
Loop2:
        mrmovq (%rdi), %r8
        mrmovq 8(%rdi), %r9
        mrmovq 16(%rdi), %r10
        mrmovq 24(%rdi), %r11
        rmmovq %r8, (%rsi)
        rmmovq %r9, 8(%rsi)
        rmmovq %r10, 16(%rsi)
        rmmovq %r11, 24(%rsi)
ele1:   andq %r8, %r8           # val <= 0?
        jle ele2:               # if so, goto ele1:
        iaddq $1, %rax          # count++, %rax         
ele2:   andq %r9, %r9
        jle ele3:
        iaddq $1, %rax
ele3:   andq %r10, %r10
        jle ele4:
        iaddq $1, %rax
ele4:   andq %r11, %r11
        jle Npos2:
        iaddq $1, %rax
Npos2:  iaddq $32,%rdi
        iaddq $32, %rsi
        iaddq $-4, %rdx
        iaddq $-4, %rcx
        jg Loop2
Next2:  andq %rdx,%rdx          # len <= 0?
        jle Done                # if so, goto Done:
Loop3:	mrmovq (%rdi), %rbx	# read val from src...
	rmmovq %rbx, (%rsi)	# ...and store it to dst
	andq %rbx, %rbx		# val <= 0?
	jle Npos3		# if so, goto Npos3:
	iaddq $1, %rax		# count++
Npos3:	iaddq $8, %rdi		# src++
	iaddq $8, %rsi		# dst++
	iaddq $-1, %rdx         # len--
        jg Loop3		# if so, goto Loop3:
##################################################################
# Do not modify the following section of code
# Function epilogue.
Done:
	ret
##################################################################
# Keep the following label at the end of your function
End:
#/* $end ncopy-ys */