7.8.3 C/C++ Code Access to the Upper 16 Bits of 16-Bit Multiply

The following methods provide access to the upper 16 bits of a 16-bit multiply in C/C++ language:

• Signed-results method:
int m1, m2; int result; result = ((long) m1 * (long) m2) >> 16;
• Unsigned-results method:
unsigned m1, m2; unsigned result; result = ((unsigned long) m1 * (unsigned long) m2) >> 16;

NOTE

Danger of Complicated Expressions

The compiler must recognize the structure of the expression for it to return the expected results. Avoid complicated expressions such as the following example:

((long)((unsigned)((a*b)+c)<5)*(long)(z*sin(w)>6))>>16