This intrinsic inserts a QSUB instruction or an equivalent code sequence into the instruction stream generated by the compiler. It enables you to obtain the saturating subtraction of two integers from within your C or C++ code.
The compiler might optimize your code when it detects opportunity to do so, using equivalent instructions from the same family to produce fewer instructions.
int __qsub(int val1 , int val2 )
is the minuend of the saturating subtraction operation
is the subtrahend of the saturating subtraction operation.
The __qsub intrinsic returns the saturating subtraction of val1 and val2 .
The compiler does not recognize the __qsub intrinsic when compiling for a target that does not support the QSUB instruction. The compiler generates either a warning or an error in this case, depending on the source language:
- In C code: Warning: #223-D: function "__qsub" declared implicitly.
- In C++ code: Error: #20: identifier "__qsub" is undefined.