42 lines
1 KiB
ArmAsm
42 lines
1 KiB
ArmAsm
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#
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.sect .text; .sect .rom; .sect .data; .sect .bss
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/* This is not a subroutine, but just a
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* piece of code that computes the jump-
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* address and jumps to it.
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* traps if resulting address is zero
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*
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* Stack: ( value tableaddr -- )
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*/
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.define .csa
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.csa:
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lw r4, 0(sp) /* r4 = table */
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lw r5, 0(sp) /* r5 = value */
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addiu sp, sp, 8
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lw r6, 0(r4) /* r6 = default target */
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lw r7, 4(r4) /* r7 = lower bound */
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subu r5, r5, r6 /* adjust value */
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bltz r5, 1f /* jump to default if out of range */
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nop
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lw r7, 8(r4) /* fetch range */
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subu r7, r5, r7 /* compute (adjusted value - range) */
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blez r7, 1f /* jump to default if out of range */
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nop
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addiu r4, r4, 12 /* skip header */
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sll r5, r5, 2 /* value = value<<2 */
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addu r4, r4, r5 /* find address of target */
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lw r6, 0(r4) /* r6 = new target */
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1:
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beq r6, zero, 2f /* trap if null */
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nop
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jr r6 /* otherwise jump */
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nop
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2:
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j .trap_ecase
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nop
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