register
storage-class specifier are effective (C90 6.5.1, C99 and C11 6.7.1). The register
specifier affects code generation only in these ways:
-O0
is in use, the compiler allocates distinct stack memory for all variables that do not have the register
storage-class specifier; if register
is specified, the variable may have a shorter lifespan than the code would indicate and may never be placed in memory. setjmp
doesn't save the registers in all circumstances. In those cases, GCC doesn't allocate any variables in registers unless they are marked register
. GCC will not inline any functions if the -fno-inline
option is used or if -O0
is used. Otherwise, GCC may still be unable to inline a function for many reasons; the -Winline
option may be used to determine if a function has not been inlined and why not.
© Free Software Foundation
Licensed under the GNU Free Documentation License, Version 1.3.
https://gcc.gnu.org/onlinedocs/gcc-4.9.3/gcc/Hints-implementation.html