Add new file for FFT implementation

examples/fft.py

@@ -0,0 +1,47 @@
+import allo
+from allo.ir.types import float32, int32, float64
+import numpy as np
+
+N = 1024
+
+
+def fft(real: float64[N], img: float64[N], real_twid: float64[N//2], img_twid: float64[N//2]):
+
+    log: int32 = 0
+    odd: int32
+    even: int32
+    temp: float32 
+    span: int32 = N >> 1
+    rootindex: int32
+
+    while span > 0:
+        odd = span
+        while odd < N:
+            odd |= span
+            even = odd ^ span
+
+            temp = real[even] + real[odd]
+            real[odd] = real[even] - real[odd]
+            real[even] = temp
+
+            temp = img[even] + img[odd]
+            img[odd] = img[even] - img[odd]
+            img[even] = temp
+
+            rootindex = (even << log) & (N-1)
+
+            if(rootindex != 0):
+                temp = real_twid[rootindex] * real[odd] - img_twid[rootindex] * img[odd]
+
+                img[odd] = real_twid[rootindex] * img[odd] + img_twid[rootindex] * real[odd]
+                real[odd] = temp
+
+
+            odd = odd + 1
+
+        span = span >> 1
+        log = log + 1
+
+
+s = allo.customize(fft)
+mod = s.build(target="llvm")