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sum-array-64.asm
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sum-array-64.asm
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;========1=========2=========3=========4=========5=========6=========7=========8=========9=========0=========1=========2=========3=========4=========5=========6=========7**
;Author information
; Author name: Floyd Holliday
; Author email: holliday@fullerton.edu
; Author location: Costa Mesa
;Course information
; Course number: CPSC254
; Assignment number: 3
; Due date: 2017-Jul-01
;Project information
; Project title: Data Analysis
; Purpose: [Fill in a sentence here]
; Project files: sum-driver.cpp, sum-array-64.asm
;Module information
; This module's call name: sum
; Language: X86-64
; Syntax: Intel
; Date last modified: 2017-Jul-01 [Fill in the correct date here]
; Purpose: This module will compute the sum of 64-bit doubles stored in an array.
; File name: sum-array-64.asm
; Status: This module was module is ready for delivery to students who have not yet enrolled in CPSC240
; Future enhancements: Improve execution speed by parallel processing: for instance, sum odd-numbered cells and even numbered cells concurrently,
; then add the partial sums to obtain the complete sum.
; Parameters passed in: pointer to array of doubles
; integer showing count of doubles in the array
; Parameters passed out: double containing the sum of doubles in the array
;Translator information
; Linux: nasm -f elf64 -l sum-array-64.lis -o sum-array-64.o sum-array-64.asm
;References and credits
; Seyfarth, Ray. Intro to 64 Bit Assembly Programming, ISBN=978-1484921906, Chapter 11.
;Source code formatting:
; Page width: 172 columns
; Begin comments: column 61
; Optimal print specification: Landscape, 7 points or smaller, monospace, 8½x11 paper
;
;===== Begin code area =====================================================================================================================================================
;extern printf ;External C++ function for writing to standard output device. Not used in this function.
;extern scanf ;External C++ function for reading from the standard input device. Not used in this function.
global sum ;This makes sum-array callable by functions outside of this file.
segment .data ;Place initialized data here
;This segment is empty because there are no messages to output from this function.
segment .bss ;Declare pointers to un-initialized space in this segment.
;This segment is empty because there are no (new) pointers to be declared.
;===========================================================================================================================================================================
;===== Begin the application here: Compute the sum of numbers in an array passed to this function
;===========================================================================================================================================================================
segment .text ;Place executable instructions in this segment.
sum: ;Entry point. Execution begins here.
;The next two instructions are performed at the start of every assembly program.
push rbp ;This marks the start of a new stack frame belonging to this execution of this function.
mov rbp, rsp ;rbp holds the address of the start of this new stack frame. When this function returns to its caller rbp must
;hold the same value it holds now.
;=========== Back up incoming parameters ===================================================================================================================================
mov r14, rdi ;Make a copy of the pointer to the incoming array
mov r15, rsi ;Make a second copy of the number elements in the array
;=========== Set up registers for the loop that follows ====================================================================================================================
mov qword rcx, 0 ;The loop counter is initialized to zero
push qword 0 ;Push 64 zero bits on the stack
movsd xmm8, [rsp] ;Zero out the accumulating register
pop rax ;Reverse the previous push
;===== Begin loop that will sum all numbers in the array ===================================================================================================================
begin_loop:
cmp rcx, r15 ;Determine if the loop should continue or exit
jge end_loop ;Exit from loop
mov r8, [r14] ;Copy one number from the array to a general purpose register
push r8 ;Put that number on top of the stack
movsd xmm9, [rsp] ;Copy that same floating point number to a 64-bit floating point register
pop rax ;Return the stack to the state it held before the recent push
addsd xmm8, xmm9 ;Add the floating point number to the accumulator
inc rcx ;Increment the loop counter
add r14, 8 ;Advance the pointer to the next position in the array
jmp begin_loop ;Continue executing at the beginning of the loop
end_loop: ;A marker for the lower boundary of the loop
;===== The loop has finished. Prepare to exit from this function ==========================================================================================================
movsd xmm0, xmm8 ;Copy the accumulated sum to the register designated for return values
pop rbp ;Resort to rbp the value it had in the function that called this assembly function.
ret ;Pop the stack into the rip register which is the register of the next instrucction.
;========== End of function sum-array.asm ==================================================================================================================================
;========1=========2=========3=========4=========5=========6=========7=========8=========9=========0=========1=========2=========3=========4=========5=========6=========7**