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# Read a character from stdin, save it to a local on the stack, write it to stdout.
#
# To run (from the subx directory):
# $ ./subx translate examples/ex5.subx -o examples/ex5
# $ ./subx run examples/ex5
== code 0x09000000
# instruction effective address register displacement immediate
# . op subop mod rm32 base index scale r32
# . 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes
Entry:
# allocate x on the stack
81 5/subop/subtract 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # subtract from ESP
# syscall(read, stdin, x, 1)
# . fd = 0 (stdin)
bb/copy-to-EBX 0/imm32
# . data = x (location to write result to)
8d/copy-address 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none 1/r32/ECX 4/disp8 . # copy ESP+4 to ECX
# . size = 1 character
ba/copy-to-EDX 1/imm32
# . syscall
b8/copy-to-EAX 3/imm32/read
cd/syscall 0x80/imm8
# syscall(write, stdout, x, 1)
# . fd = 1 (stdout)
bb/copy-to-EBX 1/imm32
# . data = x (location to read from)
8d/copy-address 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none 1/r32/ECX 4/disp8 . # copy ESP+4 to ECX
# . size = 1 character
ba/copy-to-EDX 1/imm32
# . syscall
b8/copy-to-EAX 4/imm32/write
cd/syscall 0x80/imm8
# syscall(exit, EBX)
b8/copy-to-EAX 1/imm32/exit
cd/syscall 0x80/imm8
# . . vim:nowrap:textwidth=0
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