Integer math on SPARCs

[Theodore A. Camus]

> Whenever two integer variables are multiplied together, the assembly 
> code generated by the C compiler (both Sun's and gcc) generate the line:
>
>		call	.mul, 2
>
> rather than use the integer multiply operation. Why is that? Floating
> point multiplies generate an fmuld assembler instruction. What's going on?

Simple - in keeping with the RISC philosophy, there is no integer multiply
instruction on the SPARC ALU.  The ".mul" routine computes multiplication
literally by shifts and adds, just like we learned in 3rd grade.  There is
actually a "mulscc" instruction which does a shift and add in a single
cycle.  (There is also a .umul for unsigned multiplication, as well as
.div, .udiv, .rem, and .urem.)

- Ted

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