[rom_ctrl,util] Make collision check faster in scramble_image.py

Update the collision check implementation using a dict to traverse the
chunks only once.

Signed-off-by: Emmanuel Blot <[email protected]>

hw/ip/rom_ctrl/util/mem.py

@@ -6,6 +6,7 @@
 import re
 import subprocess
 import tempfile
+from itertools import combinations
 from typing import Any, BinaryIO, Dict, IO, List, Optional, TextIO, Tuple
 
 from elftools.elf.elffile import ELFFile  # type: ignore
@@ -331,16 +332,15 @@ def collisions(self) -> List[Tuple[int, int]]:
         such addresses where addr0 < addr1 and in ascending order of addr0.
 
         '''
-        ret = []
-        for idx0, chunk0 in enumerate(self.chunks):
-            for off0, word0 in enumerate(chunk0.words):
-                for diff_idx, chunk1 in enumerate(self.chunks[idx0:]):
-                    first_off1 = 0 if diff_idx else off0 + 1
-                    for diff_off, word1 in enumerate(chunk1.words[first_off1:]):
-                        off1 = first_off1 + diff_off
-
-                        if word0 == word1:
-                            addr0 = chunk0.base_addr + off0
-                            addr1 = chunk1.base_addr + off1
-                            ret.append((addr0, addr1))
-        return ret
+        data = {}  # type: Dict[int, List[int]]
+        for chunk in self.chunks:
+            addr = chunk.base_addr
+            for off, word in enumerate(chunk.words):
+                if word not in data:
+                    data[word] = []
+                data[word].append(addr + off)
+        ret = []  # type: List[Tuple[int, int]]
+        for addrs in data.values():
+            if len(addrs) > 1:
+                ret.extend(combinations(addrs, 2))
+        return list(sorted(ret))