mem-cache: Fix integer promotion of mask

When applying the bitwise not to a short integer the compiler
automatically promotes it to an integer. For example, if a 8-bit
mask=0xFF, and the compiler decides to promote the mask to 32-bit
to apply the bitwise not, ~mask=0xFFFFFF00, which will yield wrong
results for popcount(): expected=0, got=24.

Change-Id: I95efba5532c27ca004ff6947d4b51a8a14f09741
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/33374
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/mem/cache/compressors/dictionary_compressor.hh

@@ -464,7 +464,7 @@ class DictionaryCompressor<T>::MaskedPattern
         const DictionaryEntry bytes,
         const bool allocate = true)
       : DictionaryCompressor<T>::Pattern(number, code, metadata_length,
-            popCount(~mask), match_location, allocate),
+            popCount(static_cast<T>(~mask)), match_location, allocate),
         bits(DictionaryCompressor<T>::fromDictionaryEntry(bytes) & ~mask)
     {
     }