Make profiling work with multiple capabilities (+RTS -N)

This means that both time and heap profiling work for parallel
programs.  Main internal changes:

  - CCCS is no longer a global variable; it is now another
    pseudo-register in the StgRegTable struct.  Thus every
    Capability has its own CCCS.

  - There is a new built-in CCS called "IDLE", which records ticks for
    Capabilities in the idle state.  If you profile a single-threaded
    program with +RTS -N2, you'll see about 50% of time in "IDLE".

  - There is appropriate locking in rts/Profiling.c to protect the
    shared cost-centre-stack data structures.

This patch does enough to get it working, I have cut one big corner:
the cost-centre-stack data structure is still shared amongst all
Capabilities, which means that multiple Capabilities will race when
updating the "allocations" and "entries" fields of a CCS.  Not only
does this give unpredictable results, but it runs very slowly due to
cache line bouncing.

It is strongly recommended that you use -fno-prof-count-entries to
disable the "entries" count when profiling parallel programs. (I shall
add a note to this effect to the docs).

1 files changed, 4 insertions, 3 deletions

diff --git a/compiler/codeGen/CgClosure.lhs b/compiler/codeGen/CgClosure.lhs
index 243d59f5db..7bad8516d9 100644
--- a/compiler/codeGen/CgClosure.lhs
+++ b/compiler/codeGen/CgClosure.lhs
@@ -316,9 +316,10 @@ mkFunEntryCode cl_info cc reg_args stk_args sp_top reg_save_code body = do
         -- Do the business
   ; funWrapper cl_info reg_args reg_save_code $ do
 	{ tickyEnterFun cl_info
-        ; enterCostCentreFun cc $
-              CmmMachOp mo_wordSub [ CmmReg nodeReg
-                                   , CmmLit (mkIntCLit (funTag cl_info)) ]
+        ; enterCostCentreFun cc
+              (CmmMachOp mo_wordSub [ CmmReg nodeReg
+                                    , CmmLit (mkIntCLit (funTag cl_info)) ])
+              (node : map snd reg_args) -- live regs
 
         ; cgExpr body }
   }