(sign_extract:m loc size pos
- This represents a reference to a sign-extended bit-field contained or
starting in loc (a memory or register reference). The bit-field
is size bits wide and starts at bit pos. The compilation
BITS_BIG_ENDIANsays which end of the memory unit pos counts from.
If loc is in memory, its mode must be a single-byte integer mode. If loc is in a register, the mode to use is specified by the operand of the
extvpattern (see Standard Names) and is usually a full-word integer mode, which is the default if none is specified.
The mode of pos is machine-specific and is also specified in the
The mode m is the same as the mode that would be used for loc if it were a register.
sign_extractcan not appear as an lvalue, or part thereof, in RTL.
(zero_extract:m loc size pos
sign_extractbut refers to an unsigned or zero-extended bit-field. The same sequence of bits are extracted, but they are filled to an entire word with zeros instead of by sign-extension.
sign_extract, this type of expressions can be lvalues in RTL; they may appear on the left side of an assignment, indicating insertion of a value into the specified bit-field.