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Support structs with bitfields in Text.LLVM.DebugUtils #90

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Dec 6, 2021
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Support structs with bitfields in Text.LLVM.DebugUtils #90

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144 changes: 129 additions & 15 deletions src/Text/LLVM/DebugUtils.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,8 @@ Point-of-contact : emertens
-}
module Text.LLVM.DebugUtils
( -- * Definition type analyzer
Info(..), computeFunctionTypes, valMdToInfo
Info(..), StructFieldInfo(..), BitfieldInfo(..), UnionFieldInfo(..)
, computeFunctionTypes, valMdToInfo
, localVariableNameDeclarations

-- * Metadata lookup
Expand All @@ -27,6 +28,7 @@ module Text.LLVM.DebugUtils

import Control.Applicative ((<|>))
import Control.Monad ((<=<))
import Data.Bits (Bits(..))
import Data.IntMap (IntMap)
import qualified Data.IntMap as IntMap
import Data.List (elemIndex, tails, stripPrefix)
Expand Down Expand Up @@ -56,13 +58,99 @@ type MdMap = IntMap ValMd

data Info
= Pointer Info
| Structure [(String,Word64,Info)] -- ^ Fields: name, bit-offset, info
| Union [(String,Info)]
| Structure [StructFieldInfo]
| Union [UnionFieldInfo]
| ArrInfo Info
| BaseType String
| Unknown
deriving Show

-- | Record debug information about a field in a struct type.
data StructFieldInfo = StructFieldInfo
{ sfiName :: String
-- ^ The field name.
, sfiOffset :: Word64
-- ^ The field's offset (in bits) from the start of the struct.
, sfiBitfield :: Maybe BitfieldInfo
-- ^ If this field resides within a bitfield, this is
-- @'Just' bitfieldInfo@. Otherwise, this is 'Nothing'.
, sfiInfo :: Info
-- ^ The debug 'Info' associated with the field's type.
} deriving Show

-- | Record debug information about a field within a bitfield. For example,
-- the following C struct:
--
-- @
-- struct s {
-- int32_t w;
-- uint8_t x1:1;
-- uint8_t x2:2;
-- uint8_t y:1;
-- int32_t z;
-- };
-- @
--
-- Corresponds to the following 'Info':
--
-- @
-- 'Structure'
-- [ 'StructFieldInfo' { 'sfiName' = \"w\"
-- , 'sfiOffset' = 0
-- , 'sfiBitfield' = Nothing
-- , 'sfiInfo' = 'BaseType' \"int32_t\"
-- }
-- , 'StructFieldInfo' { 'sfiName' = \"x1\"
-- , 'sfiOffset' = 32
-- , 'sfiBitfield' = Just ('BitfieldInfo' { 'biFieldSize' = 1
-- , 'biBitfieldOffset' = 32
-- })
-- , 'sfiInfo' = 'BaseType' \"uint8_t\"
-- }
-- , 'StructFieldInfo' { 'sfiName' = \"x2\"
-- , 'sfiOffset' = 33
-- , 'sfiBitfield' = Just ('BitfieldInfo' { 'biFieldSize' = 2
-- , 'biBitfieldOffset' = 32
-- })
-- , 'sfiInfo' = BaseType \"uint8_t\"
-- }
-- , 'StructFieldInfo' { 'sfiName' = \"y\"
-- , 'sfiOffset' = 35
-- , 'sfiBitfield' = Just ('BitfieldInfo' { 'biFieldSize' = 1
-- , 'biBitfieldOffset' = 32
-- })
-- , 'sfiInfo' = 'BaseType' \"uint8_t\"
-- }
-- , 'StructFieldInfo' { 'sfiName' = \"z\"
-- , 'sfiOffset' = 64
-- , 'sfiBitfield' = Nothing
-- , 'sfiInfo' = BaseType \"int32_t\"
-- }
-- ]
-- @
--
-- Notice that only @x1@, @x2@, and @y@ have 'BitfieldInfo's, as they are the
-- only fields that were declared with bitfield syntax.
data BitfieldInfo = BitfieldInfo
{ biFieldSize :: Word64
-- ^ The field's size (in bits) within the bitfield. This should not be
-- confused with the size of the field's declared type. For example, the
-- 'biFieldSize' of the @x1@ field is @1@, despite the fact that its
-- declared type, @uint8_t@, is otherwise 8 bits in size.
, biBitfieldOffset :: Word64
-- ^ The bitfield's offset (in bits) from the start of the struct. Note
-- that for a given field within a bitfield, its 'sfiOffset' is equal to
-- the 'biBitfieldOffset' plus the 'biFieldSize'.
} deriving Show

-- | Record debug information about a field in a union type.
data UnionFieldInfo = UnionFieldInfo
{ ufiName :: String
-- ^ The field name.
, ufiInfo :: Info
-- ^ The debug 'Info' associated with the field's type.
} deriving Show

{-
import Text.Show.Pretty
import Data.Foldable
Expand All @@ -89,6 +177,10 @@ getDebugInfo mdMap (ValMdRef i) = getDebugInfo mdMap =<< IntMap.lookup i mdMa
getDebugInfo _ (ValMdDebugInfo di) = Just di
getDebugInfo _ _ = Nothing

getInteger :: MdMap -> ValMd -> Maybe Integer
getInteger mdMap (ValMdRef i) = getInteger mdMap =<< IntMap.lookup i mdMap
getInteger _ (ValMdValue (Typed _ (ValInteger i))) = Just i
getInteger _ _ = Nothing

getList :: MdMap -> ValMd -> Maybe [Maybe ValMd]
getList mdMap (ValMdRef i) = getList mdMap =<< IntMap.lookup i mdMap
Expand Down Expand Up @@ -125,25 +217,47 @@ getFieldDIs mdMap =
traverse (getDebugInfo mdMap) <=< sequence <=< getList mdMap <=< dictElements


getStructFields :: MdMap -> DICompositeType -> Maybe [(String, Word64, Info)]
getStructFields :: MdMap -> DICompositeType -> Maybe [StructFieldInfo]
getStructFields mdMap = traverse (debugInfoToStructField mdMap) <=< getFieldDIs mdMap

debugInfoToStructField :: MdMap -> DebugInfo -> Maybe (String, Word64, Info)
debugInfoToStructField :: MdMap -> DebugInfo -> Maybe StructFieldInfo
debugInfoToStructField mdMap di =
do DebugInfoDerivedType dt <- Just di
fieldName <- didtName dt
Just (fieldName, didtOffset dt, valMdToInfo' mdMap (didtBaseType dt))


getUnionFields :: MdMap -> DICompositeType -> Maybe [(String, Info)]
-- We check if a struct field resides within a bitfield by checking its
-- `flags` field sets `BitField`, which has a numeric value of 19.
-- (https://github.com/llvm/llvm-project/blob/1bebc31c617d1a0773f1d561f02dd17c5e83b23b/llvm/include/llvm/IR/DebugInfoFlags.def#L51)
--
-- If so, the `size` field records the size in bits, and the `extraData`
-- field records the offset of the overall bitfield from the start of the
-- struct.
-- (https://github.com/llvm/llvm-project/blob/ee7652569854af567ba83e5255d70e80cc8619a1/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp#L2489-L2508)
let bitfield | testBit (didtFlags dt) 19
, Just extraData <- didtExtraData dt
, Just bitfieldOffset <- getInteger mdMap extraData
= Just $ BitfieldInfo { biFieldSize = didtSize dt
, biBitfieldOffset = fromInteger bitfieldOffset
}
| otherwise
= Nothing
Just (StructFieldInfo { sfiName = fieldName
, sfiOffset = didtOffset dt
, sfiBitfield = bitfield
, sfiInfo = valMdToInfo' mdMap (didtBaseType dt)
})


getUnionFields :: MdMap -> DICompositeType -> Maybe [UnionFieldInfo]
getUnionFields mdMap = traverse (debugInfoToUnionField mdMap) <=< getFieldDIs mdMap


debugInfoToUnionField :: MdMap -> DebugInfo -> Maybe (String, Info)
debugInfoToUnionField :: MdMap -> DebugInfo -> Maybe UnionFieldInfo
debugInfoToUnionField mdMap di =
do DebugInfoDerivedType dt <- Just di
fieldName <- didtName dt
Just (fieldName, valMdToInfo' mdMap (didtBaseType dt))
Just (UnionFieldInfo { ufiName = fieldName
, ufiInfo = valMdToInfo' mdMap (didtBaseType dt)
})



Expand Down Expand Up @@ -219,8 +333,8 @@ fieldIndexByPosition ::
Info {- ^ type information for specified field -}
fieldIndexByPosition i info =
case info of
Structure xs -> go [ x | (_,_,x) <- xs ]
Union xs -> go [ x | (_,x) <- xs ]
Structure xs -> go [ x | StructFieldInfo{sfiInfo = x} <- xs ]
Union xs -> go [ x | UnionFieldInfo{ufiInfo = x} <- xs ]
_ -> Unknown
where
go xs = case drop i xs of
Expand All @@ -235,8 +349,8 @@ fieldIndexByName ::
Maybe Int {- ^ zero-based index of field matching the name -}
fieldIndexByName n info =
case info of
Structure xs -> go [ x | (x,_,_) <- xs ]
Union xs -> go [ x | (x,_) <- xs ]
Structure xs -> go [ x | StructFieldInfo{sfiName = x} <- xs ]
Union xs -> go [ x | UnionFieldInfo{ufiName = x} <- xs ]
_ -> Nothing
where
go = elemIndex n
Expand Down