diff options
Diffstat (limited to 'compiler/codeGen/StgCmmBind.hs')
| -rw-r--r-- | compiler/codeGen/StgCmmBind.hs | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/compiler/codeGen/StgCmmBind.hs b/compiler/codeGen/StgCmmBind.hs index 16477c83dc..11b411d161 100644 --- a/compiler/codeGen/StgCmmBind.hs +++ b/compiler/codeGen/StgCmmBind.hs @@ -493,7 +493,7 @@ closureCodeBody top_lvl bndr cl_info cc args arity body fv_details tickyEnterFun cl_info ; enterCostCentreFun cc (CmmMachOp (mo_wordSub dflags) - [ CmmReg (CmmLocal node) -- not nodeReg, see #8275 + [ CmmReg (CmmLocal node) -- See [NodeReg clobbered with loopification] , mkIntExpr dflags (funTag dflags cl_info) ]) ; fv_bindings <- mapM bind_fv fv_details -- Load free vars out of closure *after* @@ -504,6 +504,18 @@ closureCodeBody top_lvl bndr cl_info cc args arity body fv_details } +-- Note [NodeReg clobbered with loopification] +-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +-- +-- Previously we used to pass nodeReg (aka R1) here. With profiling, upon +-- entering a closure, enterFunCCS was called with R1 passed to it. But since R1 +-- may get clobbered inside the body of a closure, and since a self-recursive +-- tail call does not restore R1, a subsequent call to enterFunCCS received a +-- possibly bogus value from R1. The solution is to not pass nodeReg (aka R1) to +-- enterFunCCS. Instead, we pass node, the callee-saved temporary that stores +-- the original value of R1. This way R1 may get modified but loopification will +-- not care. + -- A function closure pointer may be tagged, so we -- must take it into account when accessing the free variables. bind_fv :: (NonVoid Id, VirtualHpOffset) -> FCode (LocalReg, WordOff) @@ -780,4 +792,3 @@ closureDescription dflags mod_name name else pprModule mod_name <> char '.' <> ppr name) <> char '>') -- showSDocDump, because we want to see the unique on the Name. - |