[Git][ghc/ghc][wip/orig-thunk-info] 2 commits: compiler: Fingerprint more code generation flags
Ben Gamari (@bgamari)
gitlab at gitlab.haskell.org
Mon May 8 23:20:38 UTC 2023
Ben Gamari pushed to branch wip/orig-thunk-info at Glasgow Haskell Compiler / GHC
Commits:
70e0c8a2 by Ben Gamari at 2023-05-08T19:20:30-04:00
compiler: Fingerprint more code generation flags
Previously our recompilation check was quite inconsistent in its
coverage of non-optimisation code generation flags. Specifically, we
failed to account for most flags that would affect the behavior of
generated code in ways that might affect the result of a program's
execution (e.g. `-feager-blackholing`, `-fstrict-dicts`)
- - - - -
1d75c827 by Ben Gamari at 2023-05-08T19:20:30-04:00
compiler: Record original thunk info tables on stack
- - - - -
11 changed files:
- compiler/GHC/Cmm/CLabel.hs
- compiler/GHC/Driver/Config/StgToCmm.hs
- compiler/GHC/Driver/Flags.hs
- compiler/GHC/Driver/Session.hs
- compiler/GHC/Iface/Recomp/Flags.hs
- compiler/GHC/StgToCmm/Bind.hs
- compiler/GHC/StgToCmm/Config.hs
- docs/users_guide/debugging.rst
- rts/StgMiscClosures.cmm
- rts/include/rts/storage/Closures.h
- utils/deriveConstants/Main.hs
Changes:
=====================================
compiler/GHC/Cmm/CLabel.hs
=====================================
@@ -53,6 +53,7 @@ module GHC.Cmm.CLabel (
mkDirty_MUT_VAR_Label,
mkMUT_VAR_CLEAN_infoLabel,
mkNonmovingWriteBarrierEnabledLabel,
+ mkOrigThunkInfoLabel,
mkUpdInfoLabel,
mkBHUpdInfoLabel,
mkIndStaticInfoLabel,
@@ -641,7 +642,7 @@ mkBlockInfoTableLabel name c = IdLabel name c BlockInfoTable
-- Constructing Cmm Labels
mkDirty_MUT_VAR_Label,
mkNonmovingWriteBarrierEnabledLabel,
- mkUpdInfoLabel,
+ mkOrigThunkInfoLabel, mkUpdInfoLabel,
mkBHUpdInfoLabel, mkIndStaticInfoLabel, mkMainCapabilityLabel,
mkMAP_FROZEN_CLEAN_infoLabel, mkMAP_FROZEN_DIRTY_infoLabel,
mkMAP_DIRTY_infoLabel,
@@ -655,6 +656,7 @@ mkDirty_MUT_VAR_Label,
mkDirty_MUT_VAR_Label = mkForeignLabel (fsLit "dirty_MUT_VAR") Nothing ForeignLabelInExternalPackage IsFunction
mkNonmovingWriteBarrierEnabledLabel
= CmmLabel rtsUnitId (NeedExternDecl False) (fsLit "nonmoving_write_barrier_enabled") CmmData
+mkOrigThunkInfoLabel = CmmLabel rtsUnitId (NeedExternDecl False) (fsLit "stg_orig_thunk_info_frame") CmmInfo
mkUpdInfoLabel = CmmLabel rtsUnitId (NeedExternDecl False) (fsLit "stg_upd_frame") CmmInfo
mkBHUpdInfoLabel = CmmLabel rtsUnitId (NeedExternDecl False) (fsLit "stg_bh_upd_frame" ) CmmInfo
mkIndStaticInfoLabel = CmmLabel rtsUnitId (NeedExternDecl False) (fsLit "stg_IND_STATIC") CmmInfo
=====================================
compiler/GHC/Driver/Config/StgToCmm.hs
=====================================
@@ -37,6 +37,7 @@ initStgToCmmConfig dflags mod = StgToCmmConfig
, stgToCmmFastPAPCalls = gopt Opt_FastPAPCalls dflags
, stgToCmmSCCProfiling = sccProfilingEnabled dflags
, stgToCmmEagerBlackHole = gopt Opt_EagerBlackHoling dflags
+ , stgToCmmOrigThunkInfo = gopt Opt_OrigThunkInfo dflags
, stgToCmmInfoTableMap = gopt Opt_InfoTableMap dflags
, stgToCmmOmitYields = gopt Opt_OmitYields dflags
, stgToCmmOmitIfPragmas = gopt Opt_OmitInterfacePragmas dflags
=====================================
compiler/GHC/Driver/Flags.hs
=====================================
@@ -5,6 +5,7 @@ module GHC.Driver.Flags
, GeneralFlag(..)
, Language(..)
, optimisationFlags
+ , codeGenFlags
-- * Warnings
, WarningGroup(..)
@@ -328,6 +329,7 @@ data GeneralFlag
| Opt_IgnoreHpcChanges
| Opt_ExcessPrecision
| Opt_EagerBlackHoling
+ | Opt_OrigThunkInfo
| Opt_NoHsMain
| Opt_SplitSections
| Opt_StgStats
@@ -473,15 +475,11 @@ data GeneralFlag
| Opt_G_NoOptCoercion
deriving (Eq, Show, Enum)
--- Check whether a flag should be considered an "optimisation flag"
--- for purposes of recompilation avoidance (see
--- Note [Ignoring some flag changes] in GHC.Iface.Recomp.Flags). Being listed here is
--- not a guarantee that the flag has no other effect. We could, and
--- perhaps should, separate out the flags that have some minor impact on
--- program semantics and/or error behavior (e.g., assertions), but
--- then we'd need to go to extra trouble (and an additional flag)
--- to allow users to ignore the optimisation level even though that
--- means ignoring some change.
+-- | The set of flags which affect optimisation for the purposes of
+-- recompilation avoidance. Specifically, these include flags which
+-- affect code generation but not the semantics of the program.
+--
+-- See Note [Ignoring some flag changes] in GHC.Iface.Recomp.Flags)
optimisationFlags :: EnumSet GeneralFlag
optimisationFlags = EnumSet.fromList
[ Opt_CallArity
@@ -489,7 +487,6 @@ optimisationFlags = EnumSet.fromList
, Opt_LateDmdAnal
, Opt_KillAbsence
, Opt_KillOneShot
- , Opt_FullLaziness
, Opt_FloatIn
, Opt_LateSpecialise
, Opt_Specialise
@@ -503,7 +500,6 @@ optimisationFlags = EnumSet.fromList
, Opt_SpecConstr
, Opt_SpecConstrKeen
, Opt_DoLambdaEtaExpansion
- , Opt_IgnoreAsserts
, Opt_DoEtaReduction
, Opt_CaseMerge
, Opt_CaseFolding
@@ -513,16 +509,12 @@ optimisationFlags = EnumSet.fromList
, Opt_EnableRewriteRules
, Opt_RegsGraph
, Opt_RegsIterative
- , Opt_PedanticBottoms
, Opt_LlvmTBAA
- , Opt_LlvmFillUndefWithGarbage
, Opt_IrrefutableTuples
, Opt_CmmSink
, Opt_CmmElimCommonBlocks
, Opt_AsmShortcutting
- , Opt_OmitYields
, Opt_FunToThunk
- , Opt_DictsStrict
, Opt_DmdTxDictSel
, Opt_Loopification
, Opt_CfgBlocklayout
@@ -531,8 +523,43 @@ optimisationFlags = EnumSet.fromList
, Opt_WorkerWrapper
, Opt_WorkerWrapperUnlift
, Opt_SolveConstantDicts
+ ]
+
+-- | The set of flags which affect code generation and can change a program's
+-- runtime behavior (other than performance). These include flags which affect:
+--
+-- * asympototic space behavior (e.g. -ffull-laziness)
+-- * user visible debugging information (e.g. info table provenance)
+-- * the ability to catch runtime errors (e.g. -fignore-asserts)
+-- * the runtime result of the program (e.g. -fomit-yields)
+-- * which code or interface file declarations are emitted
+--
+codeGenFlags :: EnumSet GeneralFlag
+codeGenFlags = EnumSet.fromList
+ [ -- Flags that affect runtime result
+ Opt_EagerBlackHoling
+ , Opt_ExcessPrecision
+ , Opt_DictsStrict
+ , Opt_PedanticBottoms
+ , Opt_OmitYields
+
+ -- Flags that affect generated code
+ , Opt_ExposeAllUnfoldings
+ , Opt_NoTypeableBinds
+
+ -- Flags that affect catching of runtime errors
, Opt_CatchNonexhaustiveCases
, Opt_IgnoreAsserts
+ , Opt_LlvmFillUndefWithGarbage
+ , Opt_DoTagInferenceChecks
+
+ -- Flags that affect space
+ , Opt_FullLaziness
+
+ -- Flags that affect debugging information
+ , Opt_DistinctConstructorTables
+ , Opt_InfoTableMap
+ , Opt_OrigThunkInfo
]
data WarningFlag =
=====================================
compiler/GHC/Driver/Session.hs
=====================================
@@ -66,6 +66,7 @@ module GHC.Driver.Session (
makeDynFlagsConsistent,
positionIndependent,
optimisationFlags,
+ codeGenFlags,
setFlagsFromEnvFile,
pprDynFlagsDiff,
flagSpecOf,
@@ -3481,6 +3482,7 @@ fFlagsDeps = [
flagSpec "do-eta-reduction" Opt_DoEtaReduction,
flagSpec "do-lambda-eta-expansion" Opt_DoLambdaEtaExpansion,
flagSpec "eager-blackholing" Opt_EagerBlackHoling,
+ flagSpec "orig-thunk-info" Opt_OrigThunkInfo,
flagSpec "embed-manifest" Opt_EmbedManifest,
flagSpec "enable-rewrite-rules" Opt_EnableRewriteRules,
flagSpec "enable-th-splice-warnings" Opt_EnableThSpliceWarnings,
=====================================
compiler/GHC/Iface/Recomp/Flags.hs
=====================================
@@ -67,7 +67,10 @@ fingerprintDynFlags hsc_env this_mod nameio =
ticky =
map (`gopt` dflags) [Opt_Ticky, Opt_Ticky_Allocd, Opt_Ticky_LNE, Opt_Ticky_Dyn_Thunk, Opt_Ticky_Tag]
- flags = ((mainis, safeHs, lang, cpp), (paths, prof, ticky, debugLevel, callerCcFilters))
+ -- Other flags which affect code generation
+ codegen = map (`gopt` dflags) (EnumSet.toList codeGenFlags)
+
+ flags = ((mainis, safeHs, lang, cpp), (paths, prof, ticky, codegen, debugLevel, callerCcFilters))
in -- pprTrace "flags" (ppr flags) $
computeFingerprint nameio flags
=====================================
compiler/GHC/StgToCmm/Bind.hs
=====================================
@@ -730,7 +730,8 @@ setupUpdate closure_info node body
lbl | bh = mkBHUpdInfoLabel
| otherwise = mkUpdInfoLabel
- pushUpdateFrame lbl (CmmReg (CmmLocal node)) body
+ pushOrigThunkInfoFrame closure_info
+ $ pushUpdateFrame lbl (CmmReg (CmmLocal node)) body
| otherwise -- A static closure
= do { tickyUpdateBhCaf closure_info
@@ -738,7 +739,8 @@ setupUpdate closure_info node body
; if closureUpdReqd closure_info
then do -- Blackhole the (updatable) CAF:
{ upd_closure <- link_caf node
- ; pushUpdateFrame mkBHUpdInfoLabel upd_closure body }
+ ; pushOrigThunkInfoFrame closure_info
+ $ pushUpdateFrame mkBHUpdInfoLabel upd_closure body }
else do {tickyUpdateFrameOmitted; body}
}
@@ -754,8 +756,7 @@ pushUpdateFrame lbl updatee body
= do
updfr <- getUpdFrameOff
profile <- getProfile
- let
- hdr = fixedHdrSize profile
+ let hdr = fixedHdrSize profile
frame = updfr + hdr + pc_SIZEOF_StgUpdateFrame_NoHdr (profileConstants profile)
--
emitUpdateFrame (CmmStackSlot Old frame) lbl updatee
@@ -773,6 +774,47 @@ emitUpdateFrame frame lbl updatee = do
emitStore (cmmOffset platform frame off_updatee) updatee
initUpdFrameProf frame
+-----------------------------------------------------------------------------
+-- Original thunk info table frames
+--
+-- Note [Original thunk info table frames]
+-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+-- In some debugging scenarios (e.g. when debugging cyclic thunks) it can be very
+-- useful to know which thunks the program is in the process of evaluating.
+-- However, in the case of updateable thunks this can be very difficult
+-- to determine since the process of blackholing overwrites the thunk's
+-- info table pointer.
+--
+-- To help in such situations we provide the -forig-thunk-info flag. This enables
+-- code generation logic which pushes a stg_orig_thunk_info_frame stack frame to
+-- accompany each update frame. As the name suggests, this frame captures the
+-- the original info table of the thunk being updated. The entry code for these
+-- frames has no operational effects; the frames merely exist as breadcrumbs
+-- for debugging.
+
+pushOrigThunkInfoFrame :: ClosureInfo -> FCode () -> FCode ()
+pushOrigThunkInfoFrame closure_info body = do
+ cfg <- getStgToCmmConfig
+ if stgToCmmOrigThunkInfo cfg
+ then do_it
+ else body
+ where
+ orig_itbl = mkLblExpr (closureInfoLabel closure_info)
+ do_it = do
+ updfr <- getUpdFrameOff
+ profile <- getProfile
+ let platform = profilePlatform profile
+ hdr = fixedHdrSize profile
+ orig_info_frame_sz =
+ hdr + pc_SIZEOF_StgOrigThunkInfoFrame_NoHdr (profileConstants profile)
+ off_orig_info = hdr + pc_OFFSET_StgOrigThunkInfoFrame_info_ptr (profileConstants profile)
+ frame_off = updfr + orig_info_frame_sz
+ frame = CmmStackSlot Old frame_off
+ --
+ emitStore frame (mkLblExpr mkOrigThunkInfoLabel)
+ emitStore (cmmOffset platform frame off_orig_info) orig_itbl
+ withUpdFrameOff frame_off body
+
-----------------------------------------------------------------------------
-- Entering a CAF
--
=====================================
compiler/GHC/StgToCmm/Config.hs
=====================================
@@ -49,6 +49,7 @@ data StgToCmmConfig = StgToCmmConfig
, stgToCmmFastPAPCalls :: !Bool -- ^
, stgToCmmSCCProfiling :: !Bool -- ^ Check if cost-centre profiling is enabled
, stgToCmmEagerBlackHole :: !Bool -- ^
+ , stgToCmmOrigThunkInfo :: !Bool -- ^ Push @stg_orig_thunk_info@ frames during thunk update.
, stgToCmmInfoTableMap :: !Bool -- ^ true means generate C Stub for IPE map, See note [Mapping
-- Info Tables to Source Positions]
, stgToCmmOmitYields :: !Bool -- ^ true means omit heap checks when no allocation is performed
=====================================
docs/users_guide/debugging.rst
=====================================
@@ -1072,6 +1072,18 @@ Checking for consistency
cases. This is helpful when debugging demand analysis or type checker bugs
which can sometimes manifest as segmentation faults.
+.. ghc-flag:: -forig-thunk-info
+ :shortdesc: Generate ``stg_orig_thunk_info`` stack frames on thunk entry
+ :type: dynamic
+
+ When debugging cyclic thunks it can be helpful to know the original
+ info table of a thunk being evaluated. This flag enables code generation logic
+ to facilitate this, producing a ``stg_orig_thunk_info`` stack frame alongside
+ the usual update frame; such ``orig_thunk`` frames have no operational
+ effect but capture the original info table of the updated thunk for inspection
+ by debugging tools. See ``Note [Original thunk info table frames]`` in
+ ``GHC.StgToCmm.Bind`` for details.
+
.. ghc-flag:: -fcheck-prim-bounds
:shortdesc: Instrument array primops with bounds checks.
:type: dynamic
=====================================
rts/StgMiscClosures.cmm
=====================================
@@ -45,6 +45,17 @@ import CLOSURE stg_ret_t_info;
import CLOSURE stg_ret_v_info;
#endif
+/* See Note [Original thunk info table frames] in GHC.StgToCmm.Bind. */
+INFO_TABLE_RET (stg_orig_thunk_info_frame, RET_SMALL,
+ W_ info_ptr,
+ W_ thunk_info_ptr)
+ /* no args => explicit stack */
+{
+ unwind Sp = W_[Sp + WDS(2)];
+ Sp_adj(2);
+ jump %ENTRY_CODE(Sp(0)) [*]; // NB. all registers live!
+}
+
/* ----------------------------------------------------------------------------
Stack underflow
------------------------------------------------------------------------- */
=====================================
rts/include/rts/storage/Closures.h
=====================================
@@ -261,6 +261,13 @@ typedef struct _StgUpdateFrame {
StgClosure *updatee;
} StgUpdateFrame;
+// Thunk update frame
+//
+// Closure types: RET_SMALL
+typedef struct _StgOrigThunkInfoFrame {
+ StgHeader header;
+ StgInfoTable *info_ptr;
+} StgOrigThunkInfoFrame;
// Closure types: RET_SMALL
typedef struct {
=====================================
utils/deriveConstants/Main.hs
=====================================
@@ -437,6 +437,7 @@ wanteds os = concat
,structField Both "StgEntCounter" "entry_count"
,closureSize Both "StgUpdateFrame"
+ ,closureSize Both "StgOrigThunkInfoFrame"
,closureSize C "StgCatchFrame"
,closureSize C "StgStopFrame"
,closureSize C "StgDeadThreadFrame"
@@ -479,6 +480,7 @@ wanteds os = concat
,structSize C "StgTSOProfInfo"
,closureField Both "StgUpdateFrame" "updatee"
+ ,closureField Both "StgOrigThunkInfoFrame" "info_ptr"
,closureField C "StgCatchFrame" "handler"
,closureField C "StgCatchFrame" "exceptions_blocked"
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/69321e899e949d1a4c7eeb881e1493d6d6e0acb8...1d75c8271a8cc3ee6ff4318d935f84e34ed44072
--
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/69321e899e949d1a4c7eeb881e1493d6d6e0acb8...1d75c8271a8cc3ee6ff4318d935f84e34ed44072
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