122 lines
2.7 KiB
ArmAsm
122 lines
2.7 KiB
ArmAsm
#include <linux/linkage.h>
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/*
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* Multiply operation for 64 bit integers, for devices with hard multiply
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* Input : Operand1[H] in Reg r5
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* Operand1[L] in Reg r6
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* Operand2[H] in Reg r7
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* Operand2[L] in Reg r8
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* Output: Result[H] in Reg r3
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* Result[L] in Reg r4
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*
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* Explaination:
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*
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* Both the input numbers are divided into 16 bit number as follows
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* op1 = A B C D
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* op2 = E F G H
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* result = D * H
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* + (C * H + D * G) << 16
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* + (B * H + C * G + D * F) << 32
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* + (A * H + B * G + C * F + D * E) << 48
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*
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* Only 64 bits of the output are considered
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*/
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.text
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.globl __muldi3
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.type __muldi3, @function
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.ent __muldi3
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__muldi3:
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addi r1, r1, -40
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/* Save the input operands on the caller's stack */
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swi r5, r1, 44
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swi r6, r1, 48
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swi r7, r1, 52
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swi r8, r1, 56
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/* Store all the callee saved registers */
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sw r20, r1, r0
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swi r21, r1, 4
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swi r22, r1, 8
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swi r23, r1, 12
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swi r24, r1, 16
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swi r25, r1, 20
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swi r26, r1, 24
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swi r27, r1, 28
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/* Load all the 16 bit values for A thru H */
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lhui r20, r1, 44 /* A */
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lhui r21, r1, 46 /* B */
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lhui r22, r1, 48 /* C */
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lhui r23, r1, 50 /* D */
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lhui r24, r1, 52 /* E */
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lhui r25, r1, 54 /* F */
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lhui r26, r1, 56 /* G */
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lhui r27, r1, 58 /* H */
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/* D * H ==> LSB of the result on stack ==> Store1 */
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mul r9, r23, r27
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swi r9, r1, 36 /* Pos2 and Pos3 */
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/* Hi (Store1) + C * H + D * G ==> Store2 ==> Pos1 and Pos2 */
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/* Store the carry generated in position 2 for Pos 3 */
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lhui r11, r1, 36 /* Pos2 */
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mul r9, r22, r27 /* C * H */
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mul r10, r23, r26 /* D * G */
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add r9, r9, r10
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addc r12, r0, r0
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add r9, r9, r11
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addc r12, r12, r0 /* Store the Carry */
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shi r9, r1, 36 /* Store Pos2 */
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swi r9, r1, 32
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lhui r11, r1, 32
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shi r11, r1, 34 /* Store Pos1 */
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/* Hi (Store2) + B * H + C * G + D * F ==> Store3 ==> Pos0 and Pos1 */
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mul r9, r21, r27 /* B * H */
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mul r10, r22, r26 /* C * G */
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mul r7, r23, r25 /* D * F */
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add r9, r9, r11
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add r9, r9, r10
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add r9, r9, r7
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swi r9, r1, 32 /* Pos0 and Pos1 */
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/* Hi (Store3) + A * H + B * G + C * F + D * E ==> Store3 ==> Pos0 */
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lhui r11, r1, 32 /* Pos0 */
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mul r9, r20, r27 /* A * H */
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mul r10, r21, r26 /* B * G */
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mul r7, r22, r25 /* C * F */
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mul r8, r23, r24 /* D * E */
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add r9, r9, r11
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add r9, r9, r10
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add r9, r9, r7
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add r9, r9, r8
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sext16 r9, r9 /* Sign extend the MSB */
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shi r9, r1, 32
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/* Move results to r3 and r4 */
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lhui r3, r1, 32
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add r3, r3, r12
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shi r3, r1, 32
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lwi r3, r1, 32 /* Hi Part */
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lwi r4, r1, 36 /* Lo Part */
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/* Restore Callee saved registers */
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lw r20, r1, r0
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lwi r21, r1, 4
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lwi r22, r1, 8
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lwi r23, r1, 12
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lwi r24, r1, 16
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lwi r25, r1, 20
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lwi r26, r1, 24
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lwi r27, r1, 28
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/* Restore Frame and return */
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rtsd r15, 8
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addi r1, r1, 40
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.size __muldi3, . - __muldi3
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.end __muldi3
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