How to get MIN_EXPR without using deprecated min operator
Andrew Pinski
pinskia@physics.uc.edu
Fri May 6 14:25:00 GMT 2005
On May 6, 2005, at 9:27 AM, chris jefferson wrote:
> Michael Cieslinski wrote:
>
>> Consider the following short program:
>>
>> #include <algorithm>
>> void Tst1(short* __restrict__ SrcP, short* __restrict__ MinP,
>> int Len)
>> {
>> for (int x=0; x<Len; x++)
>> MinP[x] = SrcP[x] <? MinP[x];
>> }
>> void Tst2(short* __restrict__ SrcP, short* __restrict__ MinP,
>> int Len)
>> {
>> for (int x=0; x<Len; x++)
>> MinP[x] = std::min(SrcP[x], MinP[x]);
>> }
>>
>>
>> If I compile it with
>> gcc41 -O2 -ftree-vectorize -ftree-vectorizer-verbose=5
>> function Tst1 gets vectorized but Tst2 not.
>>
>> The reason for this is <? results in a MIN_EXPR while std::min
>> generates a
>> conditional code.
>> My question is, how can I get a MIN_EXPR without using the deprecated
>> min <?
>> operator?
The problem with C++ is in fold as we now have to disable the
optimization
which converted "a >= b ? b : a" to MIN_EXPR.
Try the following instead:
MinP[x] = (SrcP[x]<MinP[x]) ? (short)SrcP[x] : MinP[x];
which forces this to be an rvalue instead of the normal lvalue which
should
allow fold to convert this to MIN_EXPR
-- Pinski
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