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next steps for guarded data flow analysis

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This commit is contained in:
Araq 2013-06-11 00:31:40 +02:00
commit c156f2d493
7 changed files with 330 additions and 58 deletions
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34
compiler/sempass2.nim
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@ -315,15 +315,17 @@ proc trackOperand(tracked: PEffects, n: PNode, paramType: PType) =
else:
mergeEffects(tracked, effectList.sons[exceptionEffects], n)
mergeTags(tracked, effectList.sons[tagEffects], n)
if paramType != nil and tfNotNil in paramType.flags and
op != nil and tfNotNil notin op.flags:
case impliesNotNil(tracked.guards, n)
of impUnknown:
Message(n.info, errGenerated,
"cannot prove '$1' is not nil" % n.renderTree)
of impNo:
Message(n.info, errGenerated, "'$1' is provably nil" % n.renderTree)
of impYes: discard
if paramType != nil:
if tfNotNil in paramType.flags and op != nil and tfNotNil notin op.flags:
case impliesNotNil(tracked.guards, n)
of impUnknown:
Message(n.info, errGenerated,
"cannot prove '$1' is not nil" % n.renderTree)
of impNo:
Message(n.info, errGenerated, "'$1' is provably nil" % n.renderTree)
of impYes: discard
if skipTypes(paramType, abstractInst).kind == tyVar:
invalidateFacts(tracked.guards, n)
proc breaksBlock(n: PNode): bool =
case n.kind
@ -341,16 +343,22 @@ proc breaksBlock(n: PNode): bool =
proc trackCase(tracked: PEffects, n: PNode) =
track(tracked, n.sons[0])
let oldState = tracked.init.len
let oldFacts = tracked.guards.len
let interesting = interestingCaseExpr(n.sons[0]) and warnProveField in gNotes
var inter: TIntersection = @[]
var toCover = 0
for i in 1.. <n.len:
let branch = n.sons[i]
setLen(tracked.init, oldState)
if interesting:
setLen(tracked.guards, oldFacts)
addCaseBranchFacts(tracked.guards, n, i)
for i in 0 .. <branch.len:
track(tracked, branch.sons[i])
if not breaksBlock(branch.lastSon): inc toCover
for i in oldState.. <tracked.init.len:
addToIntersection(inter, tracked.init[i])
let exh = case skipTypes(n.sons[0].Typ, abstractVarRange-{tyTypeDesc}).Kind
of tyFloat..tyFloat128, tyString:
lastSon(n).kind == nkElse
@ -361,6 +369,7 @@ proc trackCase(tracked: PEffects, n: PNode) =
for id, count in items(inter):
if count >= toCover: tracked.init.add id
# else we can't merge
setLen(tracked.guards, oldFacts)
proc trackIf(tracked: PEffects, n: PNode) =
track(tracked, n.sons[0].sons[0])
@ -453,12 +462,16 @@ proc track(tracked: PEffects, n: PNode) =
# XXX new(objWithNotNil) is not initialized properly!
for i in 0 .. <safeLen(n):
track(tracked, n.sons[i])
of nkCheckedFieldExpr:
track(tracked, n.sons[0])
if warnProveField in gNotes: checkFieldAccess(tracked.guards, n)
of nkTryStmt: trackTryStmt(tracked, n)
of nkPragma: trackPragmaStmt(tracked, n)
of nkMacroDef, nkTemplateDef: discard
of nkAsgn, nkFastAsgn:
track(tracked, n.sons[1])
initVar(tracked, n.sons[0])
invalidateFacts(tracked.guards, n.sons[0])
track(tracked, n.sons[0])
of nkVarSection:
for child in n:
@ -476,8 +489,11 @@ proc track(tracked: PEffects, n: PNode) =
else:
# loop may never execute:
let oldState = tracked.init.len
let oldFacts = tracked.guards.len
addFact(tracked.guards, n.sons[0])
track(tracked, n.sons[1])
setLen(tracked.init, oldState)
setLen(tracked.guards, oldFacts)
of nkForStmt, nkParForStmt:
# we are very conservative here and assume the loop is never executed:
let oldState = tracked.init.len