Improve hashing of expressions for CSE (reduces warnings about extendCSEnv)

[ghc-hetmet.git] / compiler / basicTypes / Name.lhs

diff --git a/compiler/basicTypes/Name.lhs b/compiler/basicTypes/Name.lhs
index 75198bb..883668b 100644 (file)
--- a/compiler/basicTypes/Name.lhs
+++ b/compiler/basicTypes/Name.lhs
@@ -260,8 +260,11 @@ localiseName n = n { n_sort = Internal }
 %************************************************************************
 
 \begin{code}
-hashName :: Name -> Int
-hashName name = getKey (nameUnique name)
+hashName :: Name -> Int                -- ToDo: should really be Word
+hashName name = getKey (nameUnique name) + 1
+       -- The +1 avoids keys with lots of zeros in the ls bits, which 
+       -- interacts badly with the cheap and cheerful multiplication in
+       -- hashExpr
 \end{code}