X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fcmm%2FCmmSpillReload.hs;h=df05a654f8c6ef791f4636adc9e2146471b2f506;hb=e9f9ec1e57d53b9302a395ce0d02c0fa59e28341;hp=c4525252531d6cd44e9a1b00ca4c61d9b4ae49f9;hpb=1e50fd4185479a62e02d987bdfcb1c62712859ca;p=ghc-hetmet.git

diff --git a/compiler/cmm/CmmSpillReload.hs b/compiler/cmm/CmmSpillReload.hs
index c452525..df05a65 100644
--- a/compiler/cmm/CmmSpillReload.hs
+++ b/compiler/cmm/CmmSpillReload.hs
@@ -31,20 +31,23 @@ import UniqSet
 import Data.Maybe
 import Prelude hiding (zip)
 
--- The point of this module is to insert spills and reloads to
--- establish the invariant that at a call (or at any proc point with
--- an established protocol) all live variables not expected in
--- registers are sitting on the stack.  We use a backward analysis to
--- insert spills and reloads.  It should be followed by a
--- forward transformation to sink reloads as deeply as possible, so as
--- to reduce register pressure.
-
--- A variable can be expected to be live in a register, live on the
--- stack, or both.  This analysis ensures that spills and reloads are
--- inserted as needed to make sure that every live variable needed
--- after a call is available on the stack.  Spills are pushed back to
--- their reaching definitions, but reloads are dropped wherever needed
--- and will have to be sunk by a later forward transformation.
+{- Note [Overview of spill/reload]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The point of this module is to insert spills and reloads to
+establish the invariant that at a call (or at any proc point with
+an established protocol) all live variables not expected in
+registers are sitting on the stack.  We use a backward analysis to
+insert spills and reloads.  It should be followed by a
+forward transformation to sink reloads as deeply as possible, so as
+to reduce register pressure.
+
+A variable can be expected to be live in a register, live on the
+stack, or both.  This analysis ensures that spills and reloads are
+inserted as needed to make sure that every live variable needed
+after a call is available on the stack.  Spills are pushed back to
+their reaching definitions, but reloads are dropped wherever needed
+and will have to be sunk by a later forward transformation.
+-}
 
 data DualLive = DualLive { on_stack :: RegSet, in_regs :: RegSet }
 
@@ -64,7 +67,7 @@ changeRegs  f live = live { in_regs  = f (in_regs  live) }
 
 dualLiveLattice :: DataflowLattice DualLive
 dualLiveLattice =
-      DataflowLattice "variables live in registers and on stack" empty add True
+      DataflowLattice "variables live in registers and on stack" empty add False
     where empty = DualLive emptyRegSet emptyRegSet
           -- | compute in the Tx monad to track whether anything has changed
           add new old = do stack <- add1 (on_stack new) (on_stack old)