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/CgHeapery.lhs | |
| 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/CgHeapery.lhs')
| -rw-r--r-- | compiler/codeGen/CgHeapery.lhs | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/compiler/codeGen/CgHeapery.lhs b/compiler/codeGen/CgHeapery.lhs index 3bba211aa1..b89452e1de 100644 --- a/compiler/codeGen/CgHeapery.lhs +++ b/compiler/codeGen/CgHeapery.lhs @@ -288,6 +288,9 @@ hpStkCheck cl_info is_fun reg_save_code code = noStmts | otherwise = oneStmt (CmmAssign nodeReg (CmmLit (CmmLabel closure_lbl))) + -- Strictly speaking, we should tag node here. But if + -- node doesn't point to the closure, the code for the closure + -- cannot depend on the value of R1 anyway, so we're safe. closure_lbl = closureLabelFromCI cl_info full_save_code = node_asst `plusStmts` reg_save_code |