47 lines
1.2 KiB
ArmAsm
47 lines
1.2 KiB
ArmAsm
#
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.sect .text; .sect .rom; .sect .data; .sect .bss
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/* Get address of element of bounds-checked array.
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*
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* Stack: ( array-adr index descriptor-adr -- element-adr )
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* Sets r2 = size of element for .los4, .sts4
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* Preserves r25 (the last volatile register)
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*
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* An array descriptor is:
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*
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* +0 lower bound
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* +4 range (upper bound - lower bound); *inclusive*
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* +8 element size
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*/
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.sect .text
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.define .aar4
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.aar4:
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lw r4, 0(sp) ! r4 = address of descriptor
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lw r5, 4(sp) ! r5 = index
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lw r6, 8(sp) ! r6 = address of array
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lw r7, 0(r4) ! r7 = lower bound
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slt at, r5, r7 ! at = index < lower bound
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bne at, zero, .trap_earray
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nop
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subu r5, r5, r7 ! adjust index for non-zero lower bound
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lw at, 4(r4) ! at = range
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slt at, at, r5 ! at = range < adjusted index
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bne at, zero, .trap_earray
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nop
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lw r2, 8(r4) ! r2 = size of element
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mul r5, r5, r2 ! scale index by size
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addu r5, r5, r6 ! calculate address of element
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sw r5, 8(sp) ! push address of element
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addiu sp, sp, 8
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jr ra
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nop
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.define .trap_earray
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.trap_earray:
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li r4, 0 ! EARRAY = 0 in h/em_abs.h
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b .trp
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