/* | |
* Signed 64-bit integer multiply. | |
* | |
* Consider WXxYZ (r1r0 x r3r2) with a long multiply: | |
* WX | |
* x YZ | |
* -------- | |
* ZW ZX | |
* YW YX | |
* | |
* The low word of the result holds ZX, the high word holds | |
* (ZW+YX) + (the high overflow from ZX). YW doesn't matter because | |
* it doesn't fit in the low 64 bits. | |
* | |
* Unlike most ARM math operations, multiply instructions have | |
* restrictions on using the same register more than once (Rd and Rm | |
* cannot be the same). | |
*/ | |
/* mul-long vAA, vBB, vCC */ | |
FETCH r0, 1 @ r0<- CCBB | |
and r2, r0, #255 @ r2<- BB | |
mov r3, r0, lsr #8 @ r3<- CC | |
VREG_INDEX_TO_ADDR r2, r2 @ r2<- &fp[BB] | |
VREG_INDEX_TO_ADDR r3, r3 @ r3<- &fp[CC] | |
ldmia r2, {r0-r1} @ r0/r1<- vBB/vBB+1 | |
ldmia r3, {r2-r3} @ r2/r3<- vCC/vCC+1 | |
mul ip, r2, r1 @ ip<- ZxW | |
umull r9, r10, r2, r0 @ r9/r10 <- ZxX | |
mla r2, r0, r3, ip @ r2<- YxX + (ZxW) | |
mov r0, rINST, lsr #8 @ r0<- AA | |
add r10, r2, r10 @ r10<- r10 + low(ZxW + (YxX)) | |
VREG_INDEX_TO_ADDR r0, r0 @ r0<- &fp[AA] | |
FETCH_ADVANCE_INST 2 @ advance rPC, load rINST | |
GET_INST_OPCODE ip @ extract opcode from rINST | |
stmia r0, {r9-r10} @ vAA/vAA+1<- r9/r10 | |
GOTO_OPCODE ip @ jump to next instruction |