47 lines
1.2 KiB
Text
47 lines
1.2 KiB
Text
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# Modification of asum code to compute absolute values of entries.
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# This version uses a conditional jump
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# Execution begins at address 0
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.pos 0
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irmovq stack, %rsp # Set up stack pointer
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call main # Execute main program
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halt # Terminate program
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# Array of 4 elements
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.align 8
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array: .quad 0x0000000d000d000d
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.quad 0xffffff3fff3fff40 # -0x000000c000c000c0
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.quad 0x00000b000b000b00
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.quad 0xffff5fff5fff6000 # -0x0000a000a000a000
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main: irmovq array,%rdi
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irmovq $4,%rsi
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call absSum # absSum(array, 4)
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ret
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/* $begin abs-sum-jmp-ys */
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# long absSum(long *start, long count)
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# start in %rdi, count in %rsi
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absSum:
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irmovq $8,%r8 # Constant 8
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irmovq $1,%r9 # Constant 1
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xorq %rax,%rax # sum = 0
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andq %rsi,%rsi # Set condition codes
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jmp test
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loop:
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mrmovq (%rdi),%r10 # x = *start
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xorq %r11,%r11 # Constant 0
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subq %r10,%r11 # -x
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jle pos # Skip if -x <= 0
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rrmovq %r11,%r10 # x = -x
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pos:
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addq %r10,%rax # Add to sum
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addq %r8,%rdi # start++
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subq %r9,%rsi # count--
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test:
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jne loop # Stop when 0
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ret
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/* $end abs-sum-jmp-ys */
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# The stack starts here and grows to lower addresses
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.pos 0x200
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stack:
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