in the following, += and *= are miscompiled because an optimisation
is applied that only works if the left-hand side of the assignment
is floating point.


cat <<'!' >pt.c
typedef struct Point {int x, y;} Point;
#define	PI	3.1415626535

double cos(double), sin(double);
int print(char*, ...);
Point
circlept(Point c, int r, int degrees)
{
        double rad;

        rad = (double) degrees * PI/180.0;
        c.x += cos(rad)*r;
		c.x *= cos(rad)*r;
     	c.y -= sin(rad)*r;
        print("circlerad %d %d\n", c.x, c.y);
        return c;
}
!

Reference: /n/sources/patch/applied/6c-asadd-mul
Date: Wed Jul  4 14:43:02 CES 2012
Signed-off-by: charles.forsyth@gmail.com

--- /sys/src/cmd/6c/cgen.c	Wed Jul  4 14:41:03 2012
+++ /sys/src/cmd/6c/cgen.c	Wed Jul  4 14:41:00 2012
@@ -574,7 +574,7 @@
 				reglcgen(&nod, l, Z);
 			else
 				nod = *l;
-			if(o != OASMUL && o != OASADD) {
+			if(o != OASMUL && o != OASADD || !typefd[l->type->etype]) {
 				regalloc(&nod2, r, Z);
 				gmove(&nod, &nod2);
 				gopcode(o, r->type, &nod1, &nod2);