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authorBen Gamari <ben@smart-cactus.org>2022-06-30 15:06:25 -0400
committerBen Gamari <ben@smart-cactus.org>2022-07-15 18:16:28 -0400
commitd75c540d439510491b45f64c1113762dcb251ae1 (patch)
tree6fb957684ff84c94055ea246678679003aeec1a3
parent3d5f9ba19fea5455d778d2ee9c3fdcaad77d1db7 (diff)
downloadhaskell-wip/T21708.tar.gz
Make keepAlive# out-of-linewip/T21708
This is a naive approach to fixing the unsoundness noticed in #21708. Specifically, we remove the lowering of `keepAlive#` via CorePrep and instead turn it into an out-of-line primop. This is simple, inefficient (since the continuation must now be heap allocated), but good enough for 9.4.1. We will revisit this (particiularly via #16098) in a future release. Metric Increase: T4978 T7257 T9203
-rw-r--r--compiler/GHC/Builtin/primops.txt.pp1
-rw-r--r--compiler/GHC/CoreToStg/Prep.hs33
-rw-r--r--compiler/GHC/StgToCmm/Prim.hs4
-rw-r--r--rts/PrimOps.cmm20
-rw-r--r--rts/RtsSymbols.c1
-rw-r--r--rts/include/rts/storage/Closures.h6
-rw-r--r--rts/include/stg/MiscClosures.h2
7 files changed, 31 insertions, 36 deletions
diff --git a/compiler/GHC/Builtin/primops.txt.pp b/compiler/GHC/Builtin/primops.txt.pp
index d81dd3bc92..ac03c20dbd 100644
--- a/compiler/GHC/Builtin/primops.txt.pp
+++ b/compiler/GHC/Builtin/primops.txt.pp
@@ -3307,6 +3307,7 @@ primop KeepAliveOp "keepAlive#" GenPrimOp
polymorphic type might suggest; see the section \"RuntimeRep polymorphism
in continuation-style primops\" for details. }
with
+ out_of_line = True
strictness = { \ _arity -> mkClosedDmdSig [topDmd, topDmd, strictOnceApply1Dmd] topDiv }
diff --git a/compiler/GHC/CoreToStg/Prep.hs b/compiler/GHC/CoreToStg/Prep.hs
index 583badce52..d03df0eedb 100644
--- a/compiler/GHC/CoreToStg/Prep.hs
+++ b/compiler/GHC/CoreToStg/Prep.hs
@@ -28,10 +28,7 @@ import GHC.Tc.Utils.Env
import GHC.Unit
import GHC.Builtin.Names
-import GHC.Builtin.PrimOps
-import GHC.Builtin.PrimOps.Ids (primOpId)
import GHC.Builtin.Types
-import GHC.Builtin.Types.Prim ( realWorldStatePrimTy )
import GHC.Core.Utils
import GHC.Core.Opt.Arity
@@ -1072,36 +1069,6 @@ cpeApp top_env expr
= let (terminal, args') = collect_args arg
in cpe_app env terminal (args' ++ args)
- -- See Note [keepAlive# magic].
- cpe_app env
- (Var f)
- args
- | Just KeepAliveOp <- isPrimOpId_maybe f
- , CpeApp (Type arg_lev)
- : CpeApp (Type _result_rep)
- : CpeApp (Type arg_ty)
- : CpeApp (Type result_ty)
- : CpeApp arg
- : CpeApp s0
- : CpeApp k
- : rest <- args
- = do { y <- newVar (cpSubstTy env result_ty)
- ; s2 <- newVar realWorldStatePrimTy
- ; -- beta reduce if possible
- ; (floats, k') <- case k of
- Lam s body -> cpe_app (extendCorePrepEnvExpr env s s0) body rest
- _ -> cpe_app env k (CpeApp s0 : rest)
- ; let touchId = primOpId TouchOp
- expr = Case k' y result_ty [Alt DEFAULT [] rhs]
- rhs = let scrut = mkApps (Var touchId) [Type arg_lev, Type arg_ty, arg, Var realWorldPrimId]
- in Case scrut s2 result_ty [Alt DEFAULT [] (Var y)]
- ; (floats', expr') <- cpeBody env expr
- ; return (floats `appendFloats` floats', expr')
- }
- | Just KeepAliveOp <- isPrimOpId_maybe f
- = pprPanic "invalid keepAlive# application" $
- vcat [ text "args:" <+> ppr args ]
-
-- runRW# magic
cpe_app env (Var f) (CpeApp _runtimeRep@Type{} : CpeApp _type@Type{} : CpeApp arg : rest)
| f `hasKey` runRWKey
diff --git a/compiler/GHC/StgToCmm/Prim.hs b/compiler/GHC/StgToCmm/Prim.hs
index 22367e48ff..5d459ba7ad 100644
--- a/compiler/GHC/StgToCmm/Prim.hs
+++ b/compiler/GHC/StgToCmm/Prim.hs
@@ -1632,9 +1632,7 @@ emitPrimOp cfg primop =
TraceEventBinaryOp -> alwaysExternal
TraceMarkerOp -> alwaysExternal
SetThreadAllocationCounter -> alwaysExternal
-
- -- See Note [keepAlive# magic] in GHC.CoreToStg.Prep.
- KeepAliveOp -> panic "keepAlive# should have been eliminated in CorePrep"
+ KeepAliveOp -> alwaysExternal
where
profile = stgToCmmProfile cfg
diff --git a/rts/PrimOps.cmm b/rts/PrimOps.cmm
index b865092ed1..430824e155 100644
--- a/rts/PrimOps.cmm
+++ b/rts/PrimOps.cmm
@@ -2924,3 +2924,23 @@ stg_setThreadAllocationCounterzh ( I64 counter )
StgTSO_alloc_limit(CurrentTSO) = counter + TO_I64(offset);
return ();
}
+
+
+#define KEEP_ALIVE_FRAME_FIELDS(w_,p_,info_ptr,p1,p2,c) \
+ w_ info_ptr, \
+ PROF_HDR_FIELDS(w_,p1,p2) \
+ p_ c
+
+stg_keepAlivezh ( P_ c, /* :: v */
+ P_ io /* :: IO p */ )
+{
+ STK_CHK_GEN();
+ jump stg_ap_v_fast
+ (KEEP_ALIVE_FRAME_FIELDS(,,stg_keepAlive_frame_info, CCCS, 0, c))(io);
+}
+
+INFO_TABLE_RET(stg_keepAlive_frame, RET_SMALL, KEEP_ALIVE_FRAME_FIELDS(W_,P_, info_ptr, p1, p2, c))
+ return (P_ ret)
+{
+ return (ret);
+}
diff --git a/rts/RtsSymbols.c b/rts/RtsSymbols.c
index f695cbd041..9731f4febf 100644
--- a/rts/RtsSymbols.c
+++ b/rts/RtsSymbols.c
@@ -785,6 +785,7 @@ extern char **environ;
SymI_HasDataProto(stg_raiseUnderflowzh) \
SymI_HasDataProto(stg_raiseOverflowzh) \
SymI_HasDataProto(stg_raiseIOzh) \
+ SymI_HasDataProto(stg_keepAlivezh) \
SymI_HasDataProto(stg_paniczh) \
SymI_HasDataProto(stg_absentErrorzh) \
SymI_HasDataProto(stg_readTVarzh) \
diff --git a/rts/include/rts/storage/Closures.h b/rts/include/rts/storage/Closures.h
index 09c7bfdb88..84971d92a6 100644
--- a/rts/include/rts/storage/Closures.h
+++ b/rts/include/rts/storage/Closures.h
@@ -256,6 +256,12 @@ typedef struct _StgUpdateFrame {
} StgUpdateFrame;
+// Closure types: RET_SMALL
+typedef struct {
+ StgHeader header;
+ StgClosure *c;
+} StgKeepAliveFrame;
+
// Stack frame, when we call catch one of these will be put on the stack so we
// know to handle exceptions with the supplied handler
//
diff --git a/rts/include/stg/MiscClosures.h b/rts/include/stg/MiscClosures.h
index b5efd9636b..c1f9d3e94d 100644
--- a/rts/include/stg/MiscClosures.h
+++ b/rts/include/stg/MiscClosures.h
@@ -61,6 +61,7 @@ RTS_RET(stg_unmaskAsyncExceptionszh_ret);
RTS_RET(stg_maskUninterruptiblezh_ret);
RTS_RET(stg_maskAsyncExceptionszh_ret);
RTS_RET(stg_stack_underflow_frame);
+RTS_RET(stg_keepAlive_frame);
RTS_RET(stg_restore_cccs);
RTS_RET(stg_restore_cccs_eval);
@@ -498,6 +499,7 @@ RTS_FUN_DECL(stg_raiseUnderflowzh);
RTS_FUN_DECL(stg_raiseOverflowzh);
RTS_FUN_DECL(stg_raiseIOzh);
RTS_FUN_DECL(stg_paniczh);
+RTS_FUN_DECL(stg_keepAlivezh);
RTS_FUN_DECL(stg_absentErrorzh);
RTS_FUN_DECL(stg_makeStableNamezh);