clarify swizzle pseudocode in overview

[libreriscv.git] / openpower / sv / remap.py

diff --git a/openpower/sv/remap.py b/openpower/sv/remap.py
index c14b1102a8627361c24b3fbaef664ca457cc133a..4721d8148bed66e907099bfeb5cb66d80b128548 100644 (file)
--- a/openpower/sv/remap.py
+++ b/openpower/sv/remap.py
@@ -1,37 +1,53 @@
+# Finite State Machine version of the REMAP system.  much more likely
+# to end up being actually used in actual hardware
+
+# up to three dimensions permitted
 xdim = 3
 ydim = 2
 zdim = 1
 
+VL = xdim * ydim * zdim # set total (can repeat, e.g. VL=x*y*z*4)
+
 lims = [xdim, ydim, zdim]
-idxs = [0,0,0] # starting indices
-order = [0,1,2] # experiment with different permutations, here
-offs = 2     # experiment with different offset, here
-applydim = 0
-invxyz = [1,0,0]
+idxs = [0,0,0]   # starting indices
+applydim = [1, 1]   # apply lower dims
+order = [1,0,2]  # experiment with different permutations, here
+offset = 0       # experiment with different offsetet, here
+invxyz = [0,1,0] # inversion allowed
 
-for idx in range(offs):
+# pre-prepare the index state: run for "offset" times before
+# actually starting.  this algorithm can also be used for re-entrancy
+# if exceptions occur and a REMAP has to be started from where the
+# interrupt left off.
+for idx in range(offset):
     for i in range(3):
         idxs[order[i]] = idxs[order[i]] + 1
         if (idxs[order[i]] != lims[order[i]]):
             break
-        print
         idxs[order[i]] = 0
 
-break_count = 0
+break_count = 0 # for pretty-printing
 
-for idx in range(xdim * ydim * zdim):
+for idx in range(VL):
     ix = [0] * 3
     for i in range(3):
-        if i >= applydim:
-            ix[i] = idxs[i]
+        ix[i] = idxs[i]
         if invxyz[i]:
             ix[i] = lims[i] - 1 - ix[i]
-    new_idx = ix[0] + ix[1] * xdim + ix[2] * xdim * ydim
-    print new_idx,
+    new_idx = ix[2]
+    if applydim[1]:
+        new_idx = new_idx * ydim + ix[1]
+    if applydim[0]:
+        new_idx = new_idx * xdim + ix[0]
+    print ("%d->%d" % (idx, new_idx)),
     break_count += 1
     if break_count == lims[order[0]]:
-        print
+        print ("")
         break_count = 0
+    # this is the exact same thing as the pre-preparation stage
+    # above.  step 1: count up to the limit of the current dimension
+    # step 2: if limit reached, zero it, and allow the *next* dimension
+    # to increment.  repeat for 3 dimensions.
     for i in range(3):
         idxs[order[i]] = idxs[order[i]] + 1
         if (idxs[order[i]] != lims[order[i]]):