An award is due to LDC for sunning code generation. Null points for GCC in comparison.

Cecil Ward cecil at
Sat Aug 1 02:48:20 UTC 2020

An award is due to LDC.

LDC deserves some kind of gold medal for optimising this to just 
a couple of mul instructions and the trimmings and no loop at 
all! Incredible job from LDC. with -O3

uint foo( in uint x ) { if (x ==0) return 0 else return x + foo( 
x - 1 );}

  Since the answer is n(n+1)/2 I’m not sure why there are two mul 

Golden onion for GDC, does tail-end recursion but then with -O3 
-march=native -frelease it generations an evil-looking brew of 
SIMD and a loop with some unrolling. GDC just doesn’t grok the 
algorithmic intent like LDC does. I’m assuming that induction 
variable analysis is the key that gives LDC the superb win?

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