From: Edward Z. Yang Date: Mon, 4 Apr 2011 11:57:30 +0000 (+0100) Subject: Minor documentation improvement about pointer tagging. X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=fdc606f562759bf48aef986790ced951f2c1a082 Minor documentation improvement about pointer tagging. Signed-off-by: Edward Z. Yang --- diff --git a/compiler/codeGen/StgCmmClosure.hs b/compiler/codeGen/StgCmmClosure.hs index fe09f68..d617743 100644 --- a/compiler/codeGen/StgCmmClosure.hs +++ b/compiler/codeGen/StgCmmClosure.hs @@ -304,13 +304,15 @@ type DynTag = Int -- The tag on a *pointer* {- Note [Data constructor dynamic tags] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -The family size of a data type (the number of constructors) -can be either: +The family size of a data type (the number of constructors +or the arity of a function) can be either: * small, if the family size < 2**tag_bits * big, otherwise. Small families can have the constructor tag in the tag bits. -Big families only use the tag value 1 to represent evaluatedness. -} +Big families only use the tag value 1 to represent evaluatedness. +We don't have very many tag bits: for example, we have 2 bits on +x86-32 and 3 bits on x86-64. -} isSmallFamily :: Int -> Bool isSmallFamily fam_size = fam_size <= mAX_PTR_TAG