We have noticed a rather big change in the optimizer performance starting with the version 13 compiler when targetting the Intel 64 architecture . This change is still present in the 2013SP1 update 1.
When the options /Qsave and /Qzero are both used, with some code the compiler optimizer seems can be completely turned off (i.e. /O2 or /O3 makes no difference).
This problem does not exist with the V12.0 Fortran compiler where the optimization is not affected by the conjunction of these options.
It is possible to emphasize the problem by compiling the WHET8.FOR whetstone benchmark with the options /O2 /Qsave /Qzero with both the 2011 (u5) and the 2013 SP1 u1.
In this example, there is a 3 times execution speed degradation between V12.0 and V13 or V14.
We notice the same performance drop in some other code. Removing /Qsave or /Qzero allows a correct optimization, but it cannot be done with all our code.
Is there a additional compiler option to solve this problem, or can it be considered as a bug ?
This is a big problem for us.