On Jan 6, 2008, at 8:26 AM, Liu Yu wrote: > This bug exists in math emulation for powerpc. > The macro define are mainly used by multiplication. > > When adding two unsigned operands ( r = x + y ), > the carry bit can be counted by whether r is less than x. > However, when adding three unsigned operands, this method does not > work. > > The original code below uses this method to count carry, > it apparently overlook the case of three operands. > Assume all the operands is 32-bit wide, > ( r = x + y + last_carry , x = 0, y = 0xffffffff, last_carry = 1), > then r is no less than x but it actually gets a carry. > > I tried to fix this bug, but this patch seems not that pretty. > Are there any better ideas? > Comments are always welcomed!
take a look at how include/math-emu/op-4.h implements __FP_FRAC_ADD_4 & __FP_FRAC_SUB_4. Will that fix the bug, if so we should make the code match how its done there. - k _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
