Document Several ``force_l32`` Features for Xtensa
The Xtensa target now has documentation for the ``force_l32`` named address space, attribute, and command-line option.
The Xtensa backend gained a __force_l32 named address space, a force_l32 attribute, and a -mforce-l32 command-line option for controlling sub-word memory access from instruction memory regions. This commit documents these features in the GCC manual.
In Details
This documents the Xtensa-specific __force_l32 named address space, the force_l32 attribute, and the -mforce-l32 command-line option. These features are used when the memory regions for placing machine instructions are not configured as "unified".
For Context
Some architectures, like Xtensa, have separate address spaces for instructions and data. Normally, code loads data (e.g. from a string literal) using data-access instructions. However, if the memory regions are not configured as "unified", special instructions are needed to load data from instruction memory. These features give the user more control over how the compiler accesses memory in these situations.