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] = (SrcP[x]<MinP[x]) ? SrcP[x] : MinP[x]; } void Tst3(short* __restrict__ SrcP, short* __restrict__ MinP, int Len) { for (int x=0; x<Len; x++) MinP[x] = (SrcP[x]<MinP[x]) ? (short)SrcP[x] : MinP[x]; } void Tst4(short* __restrict__ SrcP, short* __restrict__ MinP, int Len) { for (int x=0; x<Len; x++) MinP[x] = std::min(SrcP[x], MinP[x]); } void Tst5(short* __restrict__ SrcP, short* __restrict__ MinP, int Len) { for (int x=0; x<Len; x++) if (SrcP[x]<MinP[x]) MinP[x]=SrcP[x]; } If I compile it with gcc41 -O2 -ftree-vectorize -ftree-vectorizer-verbose=5 function Tst1/Tst2/Tst3 gets vectorized but Tst4/Tst5 not. The reason for this is the first three funtions result in a MIN_EXPR while std::min and the if statement generate conditional code which the vectorizer does not recognize. Michael Cieslinski -- Summary: if statement not converted to MIN_EXPR Product: gcc Version: 4.1.0 Status: UNCONFIRMED Severity: normal Priority: P2 Component: tree-optimization AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: micis at gmx dot de CC: gcc-bugs at gcc dot gnu dot org GCC build triplet: x86_64-unknown-linux-gnu GCC host triplet: x86_64-unknown-linux-gnu GCC target triplet: x86_64-unknown-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21462