From e3d1bc27902a074c1430d4afde79a3db000db076 Mon Sep 17 00:00:00 2001
From: Cheng Shao <terrorjack@type.dance>
Date: Tue, 1 Oct 2024 19:21:54 +0000
Subject: [PATCH] compiler: add PIC support to wasm backend NCG
This commit adds support for generating PIC to the wasm backend NCG.
(cherry picked from commit 61f5baa5bd6e8d0daa20af4dc7c3213a48f99019)
---
compiler/GHC/CmmToAsm/Wasm.hs | 7 +--
compiler/GHC/CmmToAsm/Wasm/Asm.hs | 79 +++++++++++++++++---------
compiler/GHC/CmmToAsm/Wasm/Types.hs | 38 ++++++++++++-
compiler/GHC/Driver/Config/CmmToAsm.hs | 3 +-
4 files changed, 93 insertions(+), 34 deletions(-)
diff --git a/compiler/GHC/CmmToAsm/Wasm.hs b/compiler/GHC/CmmToAsm/Wasm.hs
index 511af517a68..faa611e6a16 100644
--- a/compiler/GHC/CmmToAsm/Wasm.hs
+++ b/compiler/GHC/CmmToAsm/Wasm.hs
@@ -40,12 +40,11 @@ ncgWasm ::
ncgWasm ncg_config logger platform ts us loc h cmms = do
(r, s) <- streamCmmGroups ncg_config platform us cmms
outputWasm $ "# " <> string7 (fromJust $ ml_hs_file loc) <> "\n\n"
- outputWasm $ execWasmAsmM do_tail_call $ asmTellEverything TagI32 s
+ -- See Note [WasmTailCall]
+ let cfg = (defaultWasmAsmConfig s) { pic = ncgPIC ncg_config, tailcall = doTailCall ts }
+ outputWasm $ execWasmAsmM cfg $ asmTellEverything TagI32 s
pure r
where
- -- See Note [WasmTailCall]
- do_tail_call = doTailCall ts
-
outputWasm builder = do
putDumpFileMaybe
logger
diff --git a/compiler/GHC/CmmToAsm/Wasm/Asm.hs b/compiler/GHC/CmmToAsm/Wasm/Asm.hs
index cc28b65e946..b03d203dcab 100644
--- a/compiler/GHC/CmmToAsm/Wasm/Asm.hs
+++ b/compiler/GHC/CmmToAsm/Wasm/Asm.hs
@@ -35,13 +35,13 @@ import GHC.Utils.Outputable hiding ((<>))
import GHC.Utils.Panic (panic)
-- | Reads current indentation, appends result to state
-newtype WasmAsmM a = WasmAsmM (Bool -> Builder -> State Builder a)
+newtype WasmAsmM a = WasmAsmM (WasmAsmConfig -> Builder -> State Builder a)
deriving
( Functor,
Applicative,
Monad
)
- via (ReaderT Bool (ReaderT Builder (State Builder)))
+ via (ReaderT WasmAsmConfig (ReaderT Builder (State Builder)))
instance Semigroup a => Semigroup (WasmAsmM a) where
(<>) = liftA2 (<>)
@@ -49,19 +49,18 @@ instance Semigroup a => Semigroup (WasmAsmM a) where
instance Monoid a => Monoid (WasmAsmM a) where
mempty = pure mempty
--- | To tail call or not, that is the question
-doTailCall :: WasmAsmM Bool
-doTailCall = WasmAsmM $ \do_tail_call _ -> pure do_tail_call
+getConf :: WasmAsmM WasmAsmConfig
+getConf = WasmAsmM $ \conf _ -> pure conf
-- | Default indent level is none
-execWasmAsmM :: Bool -> WasmAsmM a -> Builder
-execWasmAsmM do_tail_call (WasmAsmM m) =
- execState (m do_tail_call mempty) mempty
+execWasmAsmM :: WasmAsmConfig -> WasmAsmM a -> Builder
+execWasmAsmM conf (WasmAsmM m) =
+ execState (m conf mempty) mempty
-- | Increase indent level by a tab
asmWithTab :: WasmAsmM a -> WasmAsmM a
asmWithTab (WasmAsmM m) =
- WasmAsmM $ \do_tail_call t -> m do_tail_call $! char7 '\t' <> t
+ WasmAsmM $ \conf t -> m conf $! char7 '\t' <> t
-- | Writes a single line starting with the current indent
asmTellLine :: Builder -> WasmAsmM ()
@@ -113,7 +112,8 @@ asmFromSymName = shortByteString . coerce fastStringToShortByteString
asmTellDefSym :: SymName -> WasmAsmM ()
asmTellDefSym sym = do
- asmTellTabLine $ ".hidden " <> asm_sym
+ WasmAsmConfig {..} <- getConf
+ unless pic $ asmTellTabLine $ ".hidden " <> asm_sym
asmTellTabLine $ ".globl " <> asm_sym
where
asm_sym = asmFromSymName sym
@@ -136,7 +136,7 @@ asmTellDataSectionContent ty_word c = asmTellTabLine $ case c of
<> ( case compare o 0 of
EQ -> mempty
GT -> "+" <> intDec o
- LT -> intDec o
+ LT -> panic "asmTellDataSectionContent: negative offset"
)
DataSkip i -> ".skip " <> intDec i
DataASCII s
@@ -245,14 +245,27 @@ asmTellWasmInstr ty_word instr = case instr of
WasmConst TagI32 i -> asmTellLine $ "i32.const " <> integerDec i
WasmConst TagI64 i -> asmTellLine $ "i64.const " <> integerDec i
WasmConst {} -> panic "asmTellWasmInstr: unreachable"
- WasmSymConst sym ->
- asmTellLine $
- ( case ty_word of
- TagI32 -> "i32.const "
- TagI64 -> "i64.const "
- _ -> panic "asmTellWasmInstr: unreachable"
- )
- <> asmFromSymName sym
+ WasmSymConst sym -> do
+ WasmAsmConfig {..} <- getConf
+ let
+ asm_sym = asmFromSymName sym
+ (ty_const, ty_add) = case ty_word of
+ TagI32 -> ("i32.const ", "i32.add")
+ TagI64 -> ("i64.const ", "i64.add")
+ _ -> panic "asmTellWasmInstr: invalid word type"
+ traverse_ asmTellLine $ if
+ | pic, getKey (getUnique sym) `WS.member` mbrelSyms -> [
+ "global.get __memory_base",
+ ty_const <> asm_sym <> "@MBREL",
+ ty_add
+ ]
+ | pic, getKey (getUnique sym) `WS.member` tbrelSyms -> [
+ "global.get __table_base",
+ ty_const <> asm_sym <> "@TBREL",
+ ty_add
+ ]
+ | pic -> [ "global.get " <> asm_sym <> "@GOT" ]
+ | otherwise -> [ ty_const <> asm_sym ]
WasmLoad ty (Just w) s o align ->
asmTellLine $
asmFromWasmType ty
@@ -398,12 +411,12 @@ asmTellWasmControl ty_word c = case c of
asmTellLine $ "br_table {" <> builderCommas intDec (ts <> [t]) <> "}"
-- See Note [WasmTailCall]
WasmTailCall (WasmExpr e) -> do
- do_tail_call <- doTailCall
+ WasmAsmConfig {..} <- getConf
if
- | do_tail_call,
+ | tailcall,
WasmSymConst sym <- e ->
asmTellLine $ "return_call " <> asmFromSymName sym
- | do_tail_call ->
+ | tailcall ->
do
asmTellWasmInstr ty_word e
asmTellLine $
@@ -440,13 +453,25 @@ asmTellFunc ty_word def_syms sym (func_ty, FuncBody {..}) = do
asmTellGlobals :: WasmTypeTag w -> WasmAsmM ()
asmTellGlobals ty_word = do
+ WasmAsmConfig {..} <- getConf
+ when pic $ traverse_ asmTellTabLine [
+ ".globaltype __memory_base, i32, immutable",
+ ".globaltype __table_base, i32, immutable"
+ ]
for_ supportedCmmGlobalRegs $ \reg ->
- let (sym, ty) = fromJust $ globalInfoFromCmmGlobalReg ty_word reg
- in asmTellTabLine $
+ let
+ (sym, ty) = fromJust $ globalInfoFromCmmGlobalReg ty_word reg
+ asm_sym = asmFromSymName sym
+ in do
+ asmTellTabLine $
".globaltype "
- <> asmFromSymName sym
+ <> asm_sym
<> ", "
<> asmFromSomeWasmType ty
+ when pic $ traverse_ asmTellTabLine [
+ ".import_module " <> asm_sym <> ", regs",
+ ".import_name " <> asm_sym <> ", " <> asm_sym
+ ]
asmTellLF
asmTellCtors :: WasmTypeTag w -> [SymName] -> WasmAsmM ()
@@ -494,14 +519,14 @@ asmTellProducers = do
asmTellTargetFeatures :: WasmAsmM ()
asmTellTargetFeatures = do
- do_tail_call <- doTailCall
+ WasmAsmConfig {..} <- getConf
asmTellSectionHeader ".custom_section.target_features"
asmTellVec
[ do
asmTellTabLine ".int8 0x2b"
asmTellBS feature
| feature <-
- ["tail-call" | do_tail_call]
+ ["tail-call" | tailcall]
<> [ "bulk-memory",
"mutable-globals",
"nontrapping-fptoint",
diff --git a/compiler/GHC/CmmToAsm/Wasm/Types.hs b/compiler/GHC/CmmToAsm/Wasm/Types.hs
index e00c0352601..900cdbaa958 100644
--- a/compiler/GHC/CmmToAsm/Wasm/Types.hs
+++ b/compiler/GHC/CmmToAsm/Wasm/Types.hs
@@ -45,6 +45,8 @@ module GHC.CmmToAsm.Wasm.Types
wasmStateM,
wasmModifyM,
wasmExecM,
+ WasmAsmConfig (..),
+ defaultWasmAsmConfig
)
where
@@ -136,7 +138,9 @@ data SymVisibility
SymStatic
| -- | Defined, visible to other compilation units.
--
- -- Adds @.hidden@ & @.globl@ directives in the output assembly.
+ -- Adds @.globl@ directives in the output assembly. Also adds
+ -- @.hidden@ when not generating PIC code, similar to
+ -- -fvisibility=hidden in clang.
--
-- @[ binding=global vis=hidden ]@
SymDefault
@@ -480,3 +484,35 @@ instance MonadUnique (WasmCodeGenM w) where
u <- getUniqueM
s <- WasmCodeGenM get
pure $ u:(wasmEvalM getUniquesM s)
+
+data WasmAsmConfig = WasmAsmConfig
+ {
+ pic, tailcall :: Bool,
+ -- | Data/function symbols with 'SymStatic' visibility (defined
+ -- but not visible to other compilation units). When doing PIC
+ -- codegen, private symbols must be emitted as @MBREL@/@TBREL@
+ -- relocations in the code section. The public symbols, defined or
+ -- elsewhere, are all emitted as @GOT@ relocations instead.
+ mbrelSyms, tbrelSyms :: ~SymSet
+ }
+
+-- | The default 'WasmAsmConfig' must be extracted from the final
+-- 'WasmCodeGenState'.
+defaultWasmAsmConfig :: WasmCodeGenState w -> WasmAsmConfig
+defaultWasmAsmConfig WasmCodeGenState {..} =
+ WasmAsmConfig
+ { pic = False,
+ tailcall = False,
+ mbrelSyms = mk_rel_syms dataSections,
+ tbrelSyms = mk_rel_syms funcBodies
+ }
+ where
+ mk_rel_syms :: SymMap a -> SymSet
+ mk_rel_syms =
+ nonDetFoldUniqMap
+ ( \(sym, _) acc ->
+ if getKey (getUnique sym) `WS.member` defaultSyms
+ then acc
+ else WS.insert (getKey (getUnique sym)) acc
+ )
+ WS.empty
diff --git a/compiler/GHC/Driver/Config/CmmToAsm.hs b/compiler/GHC/Driver/Config/CmmToAsm.hs
index e3452c117df..2ba14caf4bd 100644
--- a/compiler/GHC/Driver/Config/CmmToAsm.hs
+++ b/compiler/GHC/Driver/Config/CmmToAsm.hs
@@ -21,8 +21,7 @@ initNCGConfig dflags this_mod = NCGConfig
, ncgAsmContext = initSDocContext dflags PprCode
, ncgProcAlignment = cmmProcAlignment dflags
, ncgExternalDynamicRefs = gopt Opt_ExternalDynamicRefs dflags
- -- no PIC on wasm32 for now
- , ncgPIC = positionIndependent dflags && not (platformArch (targetPlatform dflags) == ArchWasm32)
+ , ncgPIC = positionIndependent dflags
, ncgInlineThresholdMemcpy = fromIntegral $ maxInlineMemcpyInsns dflags
, ncgInlineThresholdMemset = fromIntegral $ maxInlineMemsetInsns dflags
, ncgSplitSections = gopt Opt_SplitSections dflags
--
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