Intel ARCHITECTURE IA-32 - Vectorizer Switch Options; Loop Unrolling

Application Performance Tools A
A-5
Vectorizer Switch Options
The Intel C++ and Fortran Compiler can vectorize your code using the
vectorizer switch options. The options that enable the vectorizer are
the
-Qx[M,K,W,B,P] and -Qax[M,K,W,B,P] described above. The
compiler provides a number of other vectorizer switch options that
allow you to control vectorization. The latter switches require the
-Qx[M,K,W,B,P] or -Qax[M,K,W,B,P] switch to be on. The default is
off.
In addition to the
-Qx[M,K,W,B,P] or -Qax[M,K,W,B,P] switches, the
compiler provides the following vectorization control switch options:
-Qvec_report[n] Controls the vectorizer’s diagnostic levels,
where n is either 0, 1, 2, or 3.
-Qrestrict Enables pointer disambiguation with the
restrict qualifier.
Loop Unrolling
The compilers automatically unroll loops with the -Qx[M,K,W,B,P] and
-Qax[M,K,W,B,P] switches.
To disable loop unrolling, specify -
Qunroll0.
CAUTION. When you use -Qax[extensions] in
conjunction with
-Qx[extensions], the extensions
specified by
-Qx[extensions] can be used
unconditionally by the compiler, and the resulting
program will require the processor extensions to
execute properly.