Repository : ssh://darcs.haskell.org//srv/darcs/ghc On branch : master
http://hackage.haskell.org/trac/ghc/changeset/a7e0d4484189d08125083638582a6f8e4ae44801 >--------------------------------------------------------------- commit a7e0d4484189d08125083638582a6f8e4ae44801 Author: Simon Marlow <marlo...@gmail.com> Date: Tue Oct 23 13:05:28 2012 +0100 a small -fPIC optimisation (PicBaseReg + lit) + N ==> PicBaseReg + (lit+N) >--------------------------------------------------------------- compiler/cmm/CmmOpt.hs | 14 ++++++++++++++ 1 files changed, 14 insertions(+), 0 deletions(-) diff --git a/compiler/cmm/CmmOpt.hs b/compiler/cmm/CmmOpt.hs index 8436263..dffd417 100644 --- a/compiler/cmm/CmmOpt.hs +++ b/compiler/cmm/CmmOpt.hs @@ -183,6 +183,20 @@ cmmMachOpFoldM dflags mop1@(MO_Add{}) [CmmMachOp mop2@(MO_Sub{}) [arg1,arg2], ar | not (isLit arg1) && not (isPicReg arg1) = Just (cmmMachOpFold dflags mop1 [arg1, cmmMachOpFold dflags mop2 [arg3,arg2]]) +-- special case: (PicBaseReg + lit) + N ==> PicBaseReg + (lit+N) +-- +-- this is better because lit+N is a single link-time constant (e.g. a +-- CmmLabelOff), so the right-hand expression needs only one +-- instruction, whereas the left needs two. This happens when pointer +-- tagging gives us label+offset, and PIC turns the label into +-- PicBaseReg + label. +-- +cmmMachOpFoldM _ MO_Add{} [ CmmMachOp op@MO_Add{} [pic, CmmLit lit] + , CmmLit (CmmInt n rep) ] + | isPicReg pic + = Just $ CmmMachOp op [pic, CmmLit $ cmmOffsetLit lit off ] + where off = fromIntegral (narrowS rep n) + -- Make a RegOff if we can cmmMachOpFoldM _ (MO_Add _) [CmmReg reg, CmmLit (CmmInt n rep)] = Just $ cmmRegOff reg (fromIntegral (narrowS rep n)) _______________________________________________ Cvs-ghc mailing list Cvs-ghc@haskell.org http://www.haskell.org/mailman/listinfo/cvs-ghc
