diff options
| author | Simon Marlow <simonmar@microsoft.com> | 2007-07-27 10:41:57 +0000 |
|---|---|---|
| committer | Simon Marlow <simonmar@microsoft.com> | 2007-07-27 10:41:57 +0000 |
| commit | 6015a94f9108a502150565577b66c23650796639 (patch) | |
| tree | 20d499d1a9644c2c98374d99f511a4a1c2cb7d1d /compiler/codeGen/CgPrimOp.hs | |
| parent | 04d444716b2e5415fb8f13771e49f1192ef8c8f8 (diff) | |
| download | haskell-6015a94f9108a502150565577b66c23650796639.tar.gz | |
Pointer Tagging
This patch implements pointer tagging as per our ICFP'07 paper "Faster
laziness using dynamic pointer tagging". It improves performance by
10-15% for most workloads, including GHC itself.
The original patches were by Alexey Rodriguez Yakushev
<mrchebas@gmail.com>, with additions and improvements by me. I've
re-recorded the development as a single patch.
The basic idea is this: we use the low 2 bits of a pointer to a heap
object (3 bits on a 64-bit architecture) to encode some information
about the object pointed to. For a constructor, we encode the "tag"
of the constructor (e.g. True vs. False), for a function closure its
arity. This enables some decisions to be made without dereferencing
the pointer, which speeds up some common operations. In particular it
enables us to avoid costly indirect jumps in many cases.
More information in the commentary:
http://hackage.haskell.org/trac/ghc/wiki/Commentary/Rts/HaskellExecution/PointerTagging
Diffstat (limited to 'compiler/codeGen/CgPrimOp.hs')
| -rw-r--r-- | compiler/codeGen/CgPrimOp.hs | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/compiler/codeGen/CgPrimOp.hs b/compiler/codeGen/CgPrimOp.hs index d26d9c6901..e489d73646 100644 --- a/compiler/codeGen/CgPrimOp.hs +++ b/compiler/codeGen/CgPrimOp.hs @@ -183,8 +183,9 @@ emitPrimOp [res] AddrToHValueOp [arg] live = stmtC (CmmAssign (CmmLocal res) arg) -- #define dataToTagzh(r,a) r=(GET_TAG(((StgClosure *)a)->header.info)) +-- Note: argument may be tagged! emitPrimOp [res] DataToTagOp [arg] live - = stmtC (CmmAssign (CmmLocal res) (getConstrTag arg)) + = stmtC (CmmAssign (CmmLocal res) (getConstrTag (cmmUntag arg))) {- Freezing arrays-of-ptrs requires changing an info table, for the benefit of the generational collector. It needs to scavenge mutable |