5.7.7.9 Caller-saves Option

The -fcaller-saves option allows the compiler to allocate values to registers that are clobbered by function calls. If allocation to these registers takes place, extra code to save and restore the clobbered registers is generated around function calls. Allocation is performed only when better performing code is expected than would otherwise be produced.

This option is automatically enabled at optimization levels -O2, -O3, and -Os.

The -fno-caller-saves form of this option never allocates values to registers that are clobbered by functions.