U Options

u (Linux* OS)
Tells the compiler the specified symbol is undefined.
u (Windows* OS)
Disables all predefined macros and assertions.
U
Undefines any definition currently in effect for the specified macro.
undef
Disables all predefined macros.
unroll, Qunroll
Tells the compiler the maximum number of times to unroll loops.
unroll-aggressive, Qunroll-aggressive
Determines whether the compiler uses more aggressive unrolling for certain loops.
use-asm, Quse-asm
Tells the compiler to produce objects through the assembler.
use-intel-optimized-headers, Quse-intel-optimized-headers
Determines whether the performance headers directory is added to the include path search list.
use-msasm
Enables the use of blocks and entire functions of assembly code within a C or C++ file.