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111 lines
2.6 KiB
ArmAsm
111 lines
2.6 KiB
ArmAsm
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; Copyright 2018 faddenSoft. All Rights Reserved.
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; See the LICENSE.txt file for distribution terms (Apache 2.0).
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;
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; Assembler: Merlin 32
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org $1000
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; 65816 mode with short regs
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clc
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xce
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sep #$30
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mx %11
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jsr test1
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jsr test2
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jsr test3
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jsr test4
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jsr test5
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rts
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; TEST #1: simple example
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test1 lda #$00
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dfb $2c ;BIT abs
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:inner lda #$01
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beq :inner
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rts
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; TEST #2: embedded with break path
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;
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; Example inspired by incorrect analysis...
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;
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; The code analyzer sees:
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; beq {+03} ;jumps to the $8f
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; lda #$00
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; brk $8f
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; and stops, then pursues the branch. If we try to walk from top
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; to bottom, skipping forward by the full length of an instruction,
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; we'll appear to find ourselves in the middle of an embedded
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; instruction.
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;
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; This is different from the typical embedded instruction,
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; where the inner is contained entirely within the outer.
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test2 sep #$30 ;short regs
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mx %00 ;pretend they're long
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lda $00 ;load something to scramble flags
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beq :store
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lda #$0000
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:store stal $012345
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rts
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; TEST #3: embedded with non-instruction byte
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;
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; The code analyzer sees two paths, involving the three bytes.
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; The first is the three-byte JSR, the second is the one-byte
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; RTS. The third NOP byte is never "executed" by the analyzer,
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; but because of the way we display embedded instructions it
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; gets put on its own line. Since it's not an instruction start
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; or a data item, things get confused. (This is referred to as
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; an "embedded orphan" in the code.)
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test3 dfb $20 ;JSR
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:mid dfb $60 ;RTS
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dfb $ea ;NOP
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bra :mid
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; TEST #4: overlapping chain
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;
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; Each BIT instruction is three bytes, and each byte is a branch target,
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; so we get a string of embedded instructions.
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test4
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:bits hex 2c2c2c2c2c2c2c2c2ceaea
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asl
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bcc :bits
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asl
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bcc :bits+1
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asl
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bcc :bits+2
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asl
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bcc :bits+3
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asl
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bcc :bits+4
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asl
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bcc :bits+5
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asl
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bcc :bits+6
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asl
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bcc :bits+7
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asl
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bcc :bits+8
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asl
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bcc :bits+9
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rts
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; TEST #5: another overlap
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;
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; Trying to be a little different.
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test5 dfb $2c
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:mid1 nop
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hex ad
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:mid2 lda $00
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asl
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bcc :mid1
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asl
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bcc :mid2
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; TEST #6: "embedded" off the end of the file
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dfb $af ;ldal
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