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Re: GCC porting tutorials
On 04/27/2010 08:41 PM, Jonas Paulsson wrote:
>> I've recently been bitten by the lost-widening-multiplication-
>> when-in-loop issue myself, and noted it for revisit Some Day.
>> Fixing that by other means made a whopping 27% improvement for
>> the application where I saw it: a hot loop doing a MDCT using
>> Q31 fixed-point, where a common operation is to widen-multiply
>> two 32-bit numbers and pick the high 32 bits of the 64-bit
>> result (being the result divided by 2; i.e. Q30-ish for that
>> operation).
>>
>> brgds, H-P
Widening multiplies should work again after r158633 and 158643. If
there are cases that still don't work for you, please file bugzilla PRs.
Bernd