Fix missing DSP instruction alternates on Teensy LC

utility/dspinst.h

@@ -100,7 +100,7 @@ static inline int32_t multiply_32x32_rshift32(int32_t a, int32_t b)
 	asm volatile("smmul %0, %1, %2" : "=r" (out) : "r" (a), "r" (b));
 	return out;
 #elif defined(KINETISL)
-	return 0; // TODO....
+	return ((int64_t)a * (int64_t)b) >> 32;
 #endif
 }
 
@@ -113,7 +113,7 @@ static inline int32_t multiply_32x32_rshift32_rounded(int32_t a, int32_t b)
 	asm volatile("smmulr %0, %1, %2" : "=r" (out) : "r" (a), "r" (b));
 	return out;
 #elif defined(KINETISL)
-	return 0; // TODO....
+	return (((int64_t)a * (int64_t)b) + 0x8000000) >> 32;
 #endif
 }
 
@@ -126,7 +126,7 @@ static inline int32_t multiply_accumulate_32x32_rshift32_rounded(int32_t sum, in
 	asm volatile("smmlar %0, %2, %3, %1" : "=r" (out) : "r" (sum), "r" (a), "r" (b));
 	return out;
 #elif defined(KINETISL)
-	return 0; // TODO....
+	return sum + ((((int64_t)a * (int64_t)b) + 0x8000000) >> 32);
 #endif
 }
 
@@ -139,7 +139,7 @@ static inline int32_t multiply_subtract_32x32_rshift32_rounded(int32_t sum, int3
 	asm volatile("smmlsr %0, %2, %3, %1" : "=r" (out) : "r" (sum), "r" (a), "r" (b));
 	return out;
 #elif defined(KINETISL)
-	return 0; // TODO....
+	return sum - ((((int64_t)a * (int64_t)b) + 0x8000000) >> 32);
 #endif
 }