+ dSP; dATARGET; tryAMAGICbin(mult,opASSIGN);
+#ifdef PERL_PRESERVE_IVUV
+ SvIV_please(TOPs);
+ if (SvIOK(TOPs)) {
+ /* Unless the left argument is integer in range we are going to have to
+ use NV maths. Hence only attempt to coerce the right argument if
+ we know the left is integer. */
+ /* Left operand is defined, so is it IV? */
+ SvIV_please(TOPm1s);
+ if (SvIOK(TOPm1s)) {
+ bool auvok = SvUOK(TOPm1s);
+ bool buvok = SvUOK(TOPs);
+ const UV topmask = (~ (UV)0) << (4 * sizeof (UV));
+ const UV botmask = ~((~ (UV)0) << (4 * sizeof (UV)));
+ UV alow;
+ UV ahigh;
+ UV blow;
+ UV bhigh;
+
+ if (auvok) {
+ alow = SvUVX(TOPm1s);
+ } else {
+ IV aiv = SvIVX(TOPm1s);
+ if (aiv >= 0) {
+ alow = aiv;
+ auvok = TRUE; /* effectively it's a UV now */
+ } else {
+ alow = -aiv; /* abs, auvok == false records sign */
+ }
+ }
+ if (buvok) {
+ blow = SvUVX(TOPs);
+ } else {
+ IV biv = SvIVX(TOPs);
+ if (biv >= 0) {
+ blow = biv;
+ buvok = TRUE; /* effectively it's a UV now */
+ } else {
+ blow = -biv; /* abs, buvok == false records sign */
+ }
+ }
+
+ /* If this does sign extension on unsigned it's time for plan B */
+ ahigh = alow >> (4 * sizeof (UV));
+ alow &= botmask;
+ bhigh = blow >> (4 * sizeof (UV));
+ blow &= botmask;
+ if (ahigh && bhigh) {
+ /* eg 32 bit is at least 0x10000 * 0x10000 == 0x100000000
+ which is overflow. Drop to NVs below. */
+ } else if (!ahigh && !bhigh) {
+ /* eg 32 bit is at most 0xFFFF * 0xFFFF == 0xFFFE0001
+ so the unsigned multiply cannot overflow. */
+ UV product = alow * blow;
+ if (auvok == buvok) {
+ /* -ve * -ve or +ve * +ve gives a +ve result. */
+ SP--;
+ SETu( product );
+ RETURN;
+ } else if (product <= (UV)IV_MIN) {
+ /* 2s complement assumption that (UV)-IV_MIN is correct. */
+ /* -ve result, which could overflow an IV */
+ SP--;
+ SETi( -product );
+ RETURN;
+ } /* else drop to NVs below. */
+ } else {
+ /* One operand is large, 1 small */
+ UV product_middle;
+ if (bhigh) {
+ /* swap the operands */
+ ahigh = bhigh;
+ bhigh = blow; /* bhigh now the temp var for the swap */
+ blow = alow;
+ alow = bhigh;
+ }
+ /* now, ((ahigh * blow) << half_UV_len) + (alow * blow)
+ multiplies can't overflow. shift can, add can, -ve can. */
+ product_middle = ahigh * blow;
+ if (!(product_middle & topmask)) {
+ /* OK, (ahigh * blow) won't lose bits when we shift it. */
+ UV product_low;
+ product_middle <<= (4 * sizeof (UV));
+ product_low = alow * blow;
+
+ /* as for pp_add, UV + something mustn't get smaller.
+ IIRC ANSI mandates this wrapping *behaviour* for
+ unsigned whatever the actual representation*/
+ product_low += product_middle;
+ if (product_low >= product_middle) {
+ /* didn't overflow */
+ if (auvok == buvok) {
+ /* -ve * -ve or +ve * +ve gives a +ve result. */
+ SP--;
+ SETu( product_low );
+ RETURN;
+ } else if (product_low <= (UV)IV_MIN) {
+ /* 2s complement assumption again */
+ /* -ve result, which could overflow an IV */
+ SP--;
+ SETi( -product_low );
+ RETURN;
+ } /* else drop to NVs below. */
+ }
+ } /* product_middle too large */
+ } /* ahigh && bhigh */
+ } /* SvIOK(TOPm1s) */
+ } /* SvIOK(TOPs) */
+#endif