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#
#
# The Nim Compiler
# (c) Copyright 2018 Nim Contributors
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
# This file implements closure iterator transformations.
# The main idea is to split the closure iterator body to top level statements.
# The body is split by yield statement.
#
# Example:
# while a > 0:
# echo "hi"
# yield a
# dec a
#
# Should be transformed to:
# STATE0:
# if a > 0:
# echo "hi"
# :state = 1 # Next state
# return a # yield
# else:
# :state = 2 # Next state
# break :stateLoop # Proceed to the next state
# STATE1:
# dec a
# :state = 0 # Next state
# break :stateLoop # Proceed to the next state
# STATE2:
# :state = -1 # End of execution
# The transformation should play well with lambdalifting, however depending
# on situation, it can be called either before or after lambdalifting
# transformation. As such we behave slightly differently, when accessing
# iterator state, or using temp variables. If lambdalifting did not happen,
# we just create local variables, so that they will be lifted further on.
# Otherwise, we utilize existing env, created by lambdalifting.
# Lambdalifting treats :state variable specially, it should always end up
# as the first field in env. Currently C codegen depends on this behavior.
# One special subtransformation is nkStmtListExpr lowering.
# Example:
# template foo(): int =
# yield 1
# 2
#
# iterator it(): int {.closure.} =
# if foo() == 2:
# yield 3
#
# If a nkStmtListExpr has yield inside, it has first to be lowered to:
# yield 1
# :tmpSlLower = 2
# if :tmpSlLower == 2:
# yield 3
# nkTryStmt Transformations:
# If the iter has an nkTryStmt with a yield inside
# - the closure iter is promoted to have exceptions (ctx.hasExceptions = true)
# - exception table is created. This is a const array, where
# `abs(exceptionTable[i])` is a state idx to which we should jump from state
# `i` should exception be raised in state `i`. For all states in `try` block
# the target state is `except` block. For all states in `except` block
# the target state is `finally` block. For all other states there is no
# target state (0, as the first block can never be neither except nor finally).
# `exceptionTable[i]` is < 0 if `abs(exceptionTable[i])` is except block,
# and > 0, for finally block.
# - local variable :curExc is created
# - the iter body is wrapped into a
# try:
# closureIterSetupExc(:curExc)
# ...body...
# catch:
# :state = exceptionTable[:state]
# if :state == 0: raise # No state that could handle exception
# :unrollFinally = :state > 0 # Target state is finally
# if :state < 0:
# :state = -:state
# :curExc = getCurrentException()
#
# nkReturnStmt within a try/except/finally now has to behave differently as we
# want the nearest finally block to be executed before the return, thus it is
# transformed to:
# :tmpResult = returnValue (if return doesn't have a value, this is skipped)
# :unrollFinally = true
# goto nearestFinally (or -1 if not exists)
#
# Every finally block calls closureIterEndFinally() upon its successful
# completion.
#
# Example:
#
# try:
# yield 0
# raise ...
# except:
# yield 1
# return 3
# finally:
# yield 2
#
# Is transformed to (yields are left in place for example simplicity,
# in reality the code is subdivided even more, as described above):
#
# STATE0: # Try
# yield 0
# raise ...
# :state = 2 # What would happen should we not raise
# break :stateLoop
# STATE1: # Except
# yield 1
# :tmpResult = 3 # Return
# :unrollFinally = true # Return
# :state = 2 # Goto Finally
# break :stateLoop
# :state = 2 # What would happen should we not return
# break :stateLoop
# STATE2: # Finally
# yield 2
# if :unrollFinally: # This node is created by `newEndFinallyNode`
# if :curExc.isNil:
# return :tmpResult
# else:
# raise
# state = -1 # Goto next state. In this case we just exit
# break :stateLoop
import
intsets, strutils, options, ast, astalgo, trees, treetab, msgs, idents,
renderer, types, magicsys, lowerings, lambdalifting, modulegraphs, lineinfos
type
Ctx = object
g: ModuleGraph
fn: PSym
stateVarSym: PSym # :state variable. nil if env already introduced by lambdalifting
tmpResultSym: PSym # Used when we return, but finally has to interfere
unrollFinallySym: PSym # Indicates that we're unrolling finally states (either exception happened or premature return)
curExcSym: PSym # Current exception
states: seq[PNode] # The resulting states. Every state is an nkState node.
blockLevel: int # Temp used to transform break and continue stmts
stateLoopLabel: PSym # Label to break on, when jumping between states.
exitStateIdx: int # index of the last state
tempVarId: int # unique name counter
tempVars: PNode # Temp var decls, nkVarSection
exceptionTable: seq[int] # For state `i` jump to state `exceptionTable[i]` if exception is raised
hasExceptions: bool # Does closure have yield in try?
curExcHandlingState: int # Negative for except, positive for finally
nearestFinally: int # Index of the nearest finally block. For try/except it
# is their finally. For finally it is parent finally. Otherwise -1
const
nkSkip = { nkEmpty..nkNilLit, nkTemplateDef, nkTypeSection, nkStaticStmt,
nkCommentStmt } + procDefs
proc newStateAccess(ctx: var Ctx): PNode =
if ctx.stateVarSym.isNil:
result = rawIndirectAccess(newSymNode(getEnvParam(ctx.fn)),
getStateField(ctx.g, ctx.fn), ctx.fn.info)
else:
result = newSymNode(ctx.stateVarSym)
proc newStateAssgn(ctx: var Ctx, toValue: PNode): PNode =
# Creates state assignment:
# :state = toValue
newTree(nkAsgn, ctx.newStateAccess(), toValue)
proc newStateAssgn(ctx: var Ctx, stateNo: int = -2): PNode =
# Creates state assignment:
# :state = stateNo
ctx.newStateAssgn(newIntTypeNode(nkIntLit, stateNo, ctx.g.getSysType(TLineInfo(), tyInt)))
proc newEnvVar(ctx: var Ctx, name: string, typ: PType): PSym =
result = newSym(skVar, getIdent(ctx.g.cache, name), ctx.fn, ctx.fn.info)
result.typ = typ
assert(not typ.isNil)
if not ctx.stateVarSym.isNil:
# We haven't gone through labmda lifting yet, so just create a local var,
# it will be lifted later
if ctx.tempVars.isNil:
ctx.tempVars = newNodeI(nkVarSection, ctx.fn.info)
addVar(ctx.tempVars, newSymNode(result))
else:
let envParam = getEnvParam(ctx.fn)
# let obj = envParam.typ.lastSon
result = addUniqueField(envParam.typ.lastSon, result, ctx.g.cache)
proc newEnvVarAccess(ctx: Ctx, s: PSym): PNode =
if ctx.stateVarSym.isNil:
result = rawIndirectAccess(newSymNode(getEnvParam(ctx.fn)), s, ctx.fn.info)
else:
result = newSymNode(s)
proc newTmpResultAccess(ctx: var Ctx): PNode =
if ctx.tmpResultSym.isNil:
ctx.tmpResultSym = ctx.newEnvVar(":tmpResult", ctx.fn.typ[0])
ctx.newEnvVarAccess(ctx.tmpResultSym)
proc newUnrollFinallyAccess(ctx: var Ctx, info: TLineInfo): PNode =
if ctx.unrollFinallySym.isNil:
ctx.unrollFinallySym = ctx.newEnvVar(":unrollFinally", ctx.g.getSysType(info, tyBool))
ctx.newEnvVarAccess(ctx.unrollFinallySym)
proc newCurExcAccess(ctx: var Ctx): PNode =
if ctx.curExcSym.isNil:
ctx.curExcSym = ctx.newEnvVar(":curExc", ctx.g.callCodegenProc("getCurrentException", ctx.g.emptyNode).typ)
ctx.newEnvVarAccess(ctx.curExcSym)
proc newState(ctx: var Ctx, n, gotoOut: PNode): int =
# Creates a new state, adds it to the context fills out `gotoOut` so that it
# will goto this state.
# Returns index of the newly created state
result = ctx.states.len
let resLit = ctx.g.newIntLit(n.info, result)
let s = newNodeI(nkState, n.info)
s.add(resLit)
s.add(n)
ctx.states.add(s)
ctx.exceptionTable.add(ctx.curExcHandlingState)
if not gotoOut.isNil:
assert(gotoOut.len == 0)
gotoOut.add(ctx.g.newIntLit(gotoOut.info, result))
proc toStmtList(n: PNode): PNode =
result = n
if result.kind notin {nkStmtList, nkStmtListExpr}:
result = newNodeI(nkStmtList, n.info)
result.add(n)
proc addGotoOut(n: PNode, gotoOut: PNode): PNode =
# Make sure `n` is a stmtlist, and ends with `gotoOut`
result = toStmtList(n)
if result.len == 0 or result.sons[^1].kind != nkGotoState:
result.add(gotoOut)
proc newTempVar(ctx: var Ctx, typ: PType): PSym =
result = ctx.newEnvVar(":tmpSlLower" & $ctx.tempVarId, typ)
inc ctx.tempVarId
proc hasYields(n: PNode): bool =
# TODO: This is very inefficient. It traverses the node, looking for nkYieldStmt.
case n.kind
of nkYieldStmt:
result = true
of nkSkip:
discard
else:
for c in n:
if c.hasYields:
result = true
break
proc transformBreaksAndContinuesInWhile(ctx: var Ctx, n: PNode, before, after: PNode): PNode =
result = n
case n.kind
of nkSkip:
discard
of nkWhileStmt: discard # Do not recurse into nested whiles
of nkContinueStmt:
result = before
of nkBlockStmt:
inc ctx.blockLevel
result[1] = ctx.transformBreaksAndContinuesInWhile(result[1], before, after)
dec ctx.blockLevel
of nkBreakStmt:
if ctx.blockLevel == 0:
result = after
else:
for i in 0 ..< n.len:
n[i] = ctx.transformBreaksAndContinuesInWhile(n[i], before, after)
proc transformBreaksInBlock(ctx: var Ctx, n: PNode, label, after: PNode): PNode =
result = n
case n.kind
of nkSkip:
discard
of nkBlockStmt, nkWhileStmt:
inc ctx.blockLevel
result[1] = ctx.transformBreaksInBlock(result[1], label, after)
dec ctx.blockLevel
of nkBreakStmt:
if n[0].kind == nkEmpty:
if ctx.blockLevel == 0:
result = after
else:
if label.kind == nkSym and n[0].sym == label.sym:
result = after
else:
for i in 0 ..< n.len:
n[i] = ctx.transformBreaksInBlock(n[i], label, after)
proc newNullifyCurExc(ctx: var Ctx, info: TLineInfo): PNode =
# :curEcx = nil
let curExc = ctx.newCurExcAccess()
curExc.info = info
let nilnode = newNode(nkNilLit)
nilnode.typ = curExc.typ
result = newTree(nkAsgn, curExc, nilnode)
proc newOr(g: ModuleGraph, a, b: PNode): PNode {.inline.} =
result = newTree(nkCall, newSymNode(g.getSysMagic(a.info, "or", mOr)), a, b)
result.typ = g.getSysType(a.info, tyBool)
result.info = a.info
proc collectExceptState(ctx: var Ctx, n: PNode): PNode {.inline.} =
var ifStmt = newNodeI(nkIfStmt, n.info)
let g = ctx.g
for c in n:
if c.kind == nkExceptBranch:
var ifBranch: PNode
if c.len > 1:
var cond: PNode
for i in 0 .. c.len - 2:
assert(c[i].kind == nkType)
let nextCond = newTree(nkCall,
newSymNode(g.getSysMagic(c.info, "of", mOf)),
g.callCodegenProc("getCurrentException", ctx.g.emptyNode),
c[i])
nextCond.typ = ctx.g.getSysType(c.info, tyBool)
nextCond.info = c.info
if cond.isNil:
cond = nextCond
else:
cond = g.newOr(cond, nextCond)
ifBranch = newNodeI(nkElifBranch, c.info)
ifBranch.add(cond)
else:
if ifStmt.len == 0:
ifStmt = newNodeI(nkStmtList, c.info)
ifBranch = newNodeI(nkStmtList, c.info)
else:
ifBranch = newNodeI(nkElse, c.info)
ifBranch.add(c[^1])
ifStmt.add(ifBranch)
if ifStmt.len != 0:
result = newTree(nkStmtList, ctx.newNullifyCurExc(n.info), ifStmt)
else:
result = ctx.g.emptyNode
proc addElseToExcept(ctx: var Ctx, n: PNode) =
if n.kind == nkStmtList and n[1].kind == nkIfStmt and n[1][^1].kind != nkElse:
# Not all cases are covered
let branchBody = newNodeI(nkStmtList, n.info)
block: # :unrollFinally = true
branchBody.add(newTree(nkAsgn,
ctx.newUnrollFinallyAccess(n.info),
newIntTypeNode(nkIntLit, 1, ctx.g.getSysType(n.info, tyBool))))
block: # :curExc = getCurrentException()
branchBody.add(newTree(nkAsgn,
ctx.newCurExcAccess(),
ctx.g.callCodegenProc("getCurrentException", ctx.g.emptyNode)))
block: # goto nearestFinally
branchBody.add(newTree(nkGotoState, ctx.g.newIntLit(n.info, ctx.nearestFinally)))
let elseBranch = newTree(nkElse, branchBody)
n[1].add(elseBranch)
proc getFinallyNode(ctx: var Ctx, n: PNode): PNode =
result = n[^1]
if result.kind == nkFinally:
result = result[0]
else:
result = ctx.g.emptyNode
proc hasYieldsInExpressions(n: PNode): bool =
case n.kind
of nkSkip:
discard
of nkStmtListExpr:
if isEmptyType(n.typ):
for c in n:
if c.hasYieldsInExpressions:
return true
else:
result = n.hasYields
else:
for c in n:
if c.hasYieldsInExpressions:
return true
proc exprToStmtList(n: PNode): tuple[s, res: PNode] =
assert(n.kind == nkStmtListExpr)
result.s = newNodeI(nkStmtList, n.info)
result.s.sons = @[]
var n = n
while n.kind == nkStmtListExpr:
result.s.sons.add(n.sons)
result.s.sons.setLen(result.s.sons.len - 1) # delete last son
n = n[^1]
result.res = n
proc newEnvVarAsgn(ctx: Ctx, s: PSym, v: PNode): PNode =
result = newTree(nkFastAsgn, ctx.newEnvVarAccess(s), v)
result.info = v.info
proc addExprAssgn(ctx: Ctx, output, input: PNode, sym: PSym) =
if input.kind == nkStmtListExpr:
let (st, res) = exprToStmtList(input)
output.add(st)
output.add(ctx.newEnvVarAsgn(sym, res))
else:
output.add(ctx.newEnvVarAsgn(sym, input))
proc convertExprBodyToAsgn(ctx: Ctx, exprBody: PNode, res: PSym): PNode =
result = newNodeI(nkStmtList, exprBody.info)
ctx.addExprAssgn(result, exprBody, res)
proc newNotCall(g: ModuleGraph; e: PNode): PNode =
result = newTree(nkCall, newSymNode(g.getSysMagic(e.info, "not", mNot), e.info), e)
result.typ = g.getSysType(e.info, tyBool)
proc lowerStmtListExprs(ctx: var Ctx, n: PNode, needsSplit: var bool): PNode =
result = n
case n.kind
of nkSkip:
discard
of nkYieldStmt:
var ns = false
for i in 0 ..< n.len:
n[i] = ctx.lowerStmtListExprs(n[i], ns)
if ns:
result = newNodeI(nkStmtList, n.info)
let (st, ex) = exprToStmtList(n[0])
result.add(st)
n[0] = ex
result.add(n)
needsSplit = true
of nkPar, nkObjConstr, nkTupleConstr, nkBracket:
var ns = false
for i in 0 ..< n.len:
n[i] = ctx.lowerStmtListExprs(n[i], ns)
if ns:
needsSplit = true
result = newNodeI(nkStmtListExpr, n.info)
if n.typ.isNil: internalError(ctx.g.config, "lowerStmtListExprs: constr typ.isNil")
result.typ = n.typ
for i in 0 ..< n.len:
case n[i].kind
of nkExprColonExpr:
if n[i][1].kind == nkStmtListExpr:
let (st, ex) = exprToStmtList(n[i][1])
result.add(st)
n[i][1] = ex
of nkStmtListExpr:
let (st, ex) = exprToStmtList(n[i])
result.add(st)
n[i] = ex
else: discard
result.add(n)
of nkIfStmt, nkIfExpr:
var ns = false
for i in 0 ..< n.len:
n[i] = ctx.lowerStmtListExprs(n[i], ns)
if ns:
needsSplit = true
var tmp: PSym
var s: PNode
let isExpr = not isEmptyType(n.typ)
if isExpr:
tmp = ctx.newTempVar(n.typ)
result = newNodeI(nkStmtListExpr, n.info)
result.typ = n.typ
else:
result = newNodeI(nkStmtList, n.info)
var curS = result
for branch in n:
case branch.kind
of nkElseExpr, nkElse:
if isExpr:
let branchBody = newNodeI(nkStmtList, branch.info)
ctx.addExprAssgn(branchBody, branch[0], tmp)
let newBranch = newTree(nkElse, branchBody)
curS.add(newBranch)
else:
curS.add(branch)
of nkElifExpr, nkElifBranch:
var newBranch: PNode
if branch[0].kind == nkStmtListExpr:
let (st, res) = exprToStmtList(branch[0])
let elseBody = newTree(nkStmtList, st)
newBranch = newTree(nkElifBranch, res, branch[1])
let newIf = newTree(nkIfStmt, newBranch)
elseBody.add(newIf)
if curS.kind == nkIfStmt:
let newElse = newNodeI(nkElse, branch.info)
newElse.add(elseBody)
curS.add(newElse)
else:
curS.add(elseBody)
curS = newIf
else:
newBranch = branch
if curS.kind == nkIfStmt:
curS.add(newBranch)
else:
let newIf = newTree(nkIfStmt, newBranch)
curS.add(newIf)
curS = newIf
if isExpr:
let branchBody = newNodeI(nkStmtList, branch[1].info)
ctx.addExprAssgn(branchBody, branch[1], tmp)
newBranch[1] = branchBody
else:
internalError(ctx.g.config, "lowerStmtListExpr(nkIf): " & $branch.kind)
if isExpr: result.add(ctx.newEnvVarAccess(tmp))
of nkTryStmt:
var ns = false
for i in 0 ..< n.len:
n[i] = ctx.lowerStmtListExprs(n[i], ns)
if ns:
needsSplit = true
let isExpr = not isEmptyType(n.typ)
if isExpr:
result = newNodeI(nkStmtListExpr, n.info)
result.typ = n.typ
let tmp = ctx.newTempVar(n.typ)
n[0] = ctx.convertExprBodyToAsgn(n[0], tmp)
for i in 1 ..< n.len:
let branch = n[i]
case branch.kind
of nkExceptBranch:
if branch[0].kind == nkType:
branch[1] = ctx.convertExprBodyToAsgn(branch[1], tmp)
else:
branch[0] = ctx.convertExprBodyToAsgn(branch[0], tmp)
of nkFinally:
discard
else:
internalError(ctx.g.config, "lowerStmtListExpr(nkTryStmt): " & $branch.kind)
result.add(n)
result.add(ctx.newEnvVarAccess(tmp))
of nkCaseStmt:
var ns = false
for i in 0 ..< n.len:
n[i] = ctx.lowerStmtListExprs(n[i], ns)
if ns:
needsSplit = true
let isExpr = not isEmptyType(n.typ)
if isExpr:
let tmp = ctx.newTempVar(n.typ)
result = newNodeI(nkStmtListExpr, n.info)
result.typ = n.typ
if n[0].kind == nkStmtListExpr:
let (st, ex) = exprToStmtList(n[0])
result.add(st)
n[0] = ex
for i in 1 ..< n.len:
let branch = n[i]
case branch.kind
of nkOfBranch:
branch[^1] = ctx.convertExprBodyToAsgn(branch[^1], tmp)
of nkElse:
branch[0] = ctx.convertExprBodyToAsgn(branch[0], tmp)
else:
internalError(ctx.g.config, "lowerStmtListExpr(nkCaseStmt): " & $branch.kind)
result.add(n)
result.add(ctx.newEnvVarAccess(tmp))
of nkCallKinds:
var ns = false
for i in 0 ..< n.len:
n[i] = ctx.lowerStmtListExprs(n[i], ns)
if ns:
needsSplit = true
let isExpr = not isEmptyType(n.typ)
if isExpr:
result = newNodeI(nkStmtListExpr, n.info)
result.typ = n.typ
else:
result = newNodeI(nkStmtList, n.info)
if n[0].kind == nkSym and n[0].sym.magic in {mAnd, mOr}: # `and`/`or` short cirquiting
var cond = n[1]
if cond.kind == nkStmtListExpr:
let (st, ex) = exprToStmtList(cond)
result.add(st)
cond = ex
let tmp = ctx.newTempVar(cond.typ)
result.add(ctx.newEnvVarAsgn(tmp, cond))
var check = ctx.newEnvVarAccess(tmp)
if n[0].sym.magic == mOr:
check = ctx.g.newNotCall(check)
cond = n[2]
let ifBody = newNodeI(nkStmtList, cond.info)
if cond.kind == nkStmtListExpr:
let (st, ex) = exprToStmtList(cond)
ifBody.add(st)
cond = ex
ifBody.add(ctx.newEnvVarAsgn(tmp, cond))
let ifBranch = newTree(nkElifBranch, check, ifBody)
let ifNode = newTree(nkIfStmt, ifBranch)
result.add(ifNode)
result.add(ctx.newEnvVarAccess(tmp))
else:
for i in 0 ..< n.len:
if n[i].kind == nkStmtListExpr:
let (st, ex) = exprToStmtList(n[i])
result.add(st)
n[i] = ex
if n[i].kind in nkCallKinds: # XXX: This should better be some sort of side effect tracking
let tmp = ctx.newTempVar(n[i].typ)
result.add(ctx.newEnvVarAsgn(tmp, n[i]))
n[i] = ctx.newEnvVarAccess(tmp)
result.add(n)
of nkVarSection, nkLetSection:
result = newNodeI(nkStmtList, n.info)
for c in n:
let varSect = newNodeI(n.kind, n.info)
varSect.add(c)
var ns = false
c[^1] = ctx.lowerStmtListExprs(c[^1], ns)
if ns:
needsSplit = true
let (st, ex) = exprToStmtList(c[^1])
result.add(st)
c[^1] = ex
result.add(varSect)
of nkDiscardStmt, nkReturnStmt, nkRaiseStmt:
var ns = false
for i in 0 ..< n.len:
n[i] = ctx.lowerStmtListExprs(n[i], ns)
if ns:
needsSplit = true
result = newNodeI(nkStmtList, n.info)
let (st, ex) = exprToStmtList(n[0])
result.add(st)
n[0] = ex
result.add(n)
of nkCast, nkHiddenStdConv, nkHiddenSubConv, nkConv, nkObjDownConv:
var ns = false
for i in 0 ..< n.len:
n[i] = ctx.lowerStmtListExprs(n[i], ns)
if ns:
needsSplit = true
result = newNodeI(nkStmtListExpr, n.info)
result.typ = n.typ
let (st, ex) = exprToStmtList(n[^1])
result.add(st)
n[^1] = ex
result.add(n)
of nkAsgn, nkFastAsgn:
var ns = false
for i in 0 ..< n.len:
n[i] = ctx.lowerStmtListExprs(n[i], ns)
if ns:
needsSplit = true
result = newNodeI(nkStmtList, n.info)
if n[0].kind == nkStmtListExpr:
let (st, ex) = exprToStmtList(n[0])
result.add(st)
n[0] = ex
if n[1].kind == nkStmtListExpr:
let (st, ex) = exprToStmtList(n[1])
result.add(st)
n[1] = ex
result.add(n)
of nkBracketExpr:
var lhsNeedsSplit = false
var rhsNeedsSplit = false
n[0] = ctx.lowerStmtListExprs(n[0], lhsNeedsSplit)
n[1] = ctx.lowerStmtListExprs(n[1], rhsNeedsSplit)
if lhsNeedsSplit or rhsNeedsSplit:
needsSplit = true
result = newNodeI(nkStmtListExpr, n.info)
if lhsNeedsSplit:
let (st, ex) = exprToStmtList(n[0])
result.add(st)
n[0] = ex
if rhsNeedsSplit:
let (st, ex) = exprToStmtList(n[1])
result.add(st)
n[1] = ex
result.add(n)
of nkWhileStmt:
var ns = false
var condNeedsSplit = false
n[0] = ctx.lowerStmtListExprs(n[0], condNeedsSplit)
var bodyNeedsSplit = false
n[1] = ctx.lowerStmtListExprs(n[1], bodyNeedsSplit)
if condNeedsSplit or bodyNeedsSplit:
needsSplit = true
if condNeedsSplit:
let (st, ex) = exprToStmtList(n[0])
let brk = newTree(nkBreakStmt, ctx.g.emptyNode)
let branch = newTree(nkElifBranch, ctx.g.newNotCall(ex), brk)
let check = newTree(nkIfStmt, branch)
let newBody = newTree(nkStmtList, st, check, n[1])
n[0] = newSymNode(ctx.g.getSysSym(n[0].info, "true"))
n[1] = newBody
of nkDotExpr:
var ns = false
n[0] = ctx.lowerStmtListExprs(n[0], ns)
if ns:
needsSplit = true
result = newNodeI(nkStmtListExpr, n.info)
result.typ = n.typ
let (st, ex) = exprToStmtList(n[0])
result.add(st)
n[0] = ex
result.add(n)
of nkBlockExpr:
var ns = false
n[1] = ctx.lowerStmtListExprs(n[1], ns)
if ns:
needsSplit = true
result = newNodeI(nkStmtListExpr, n.info)
result.typ = n.typ
let (st, ex) = exprToStmtList(n[1])
n.kind = nkBlockStmt
n.typ = nil
n[1] = st
result.add(n)
result.add(ex)
else:
for i in 0 ..< n.len:
n[i] = ctx.lowerStmtListExprs(n[i], needsSplit)
proc newEndFinallyNode(ctx: var Ctx, info: TLineInfo): PNode =
# Generate the following code:
# if :unrollFinally:
# if :curExc.isNil:
# return :tmpResult
# else:
# raise
let curExc = ctx.newCurExcAccess()
let nilnode = newNode(nkNilLit)
nilnode.typ = curExc.typ
let cmp = newTree(nkCall, newSymNode(ctx.g.getSysMagic(info, "==", mEqRef), info), curExc, nilnode)
cmp.typ = ctx.g.getSysType(info, tyBool)
let asgn = newTree(nkFastAsgn,
newSymNode(getClosureIterResult(ctx.g, ctx.fn), info),
ctx.newTmpResultAccess())
let retStmt = newTree(nkReturnStmt, asgn)
let branch = newTree(nkElifBranch, cmp, retStmt)
# The C++ backend requires `getCurrentException` here.
let raiseStmt = newTree(nkRaiseStmt, ctx.g.callCodegenProc("getCurrentException", ctx.g.emptyNode))
raiseStmt.info = info
let elseBranch = newTree(nkElse, raiseStmt)
let ifBody = newTree(nkIfStmt, branch, elseBranch)
let elifBranch = newTree(nkElifBranch, ctx.newUnrollFinallyAccess(info), ifBody)
elifBranch.info = info
result = newTree(nkIfStmt, elifBranch)
proc transformReturnsInTry(ctx: var Ctx, n: PNode): PNode =
result = n
# TODO: This is very inefficient. It traverses the node, looking for nkYieldStmt.
case n.kind
of nkReturnStmt:
# We're somewhere in try, transform to finally unrolling
assert(ctx.nearestFinally != 0)
result = newNodeI(nkStmtList, n.info)
block: # :unrollFinally = true
let asgn = newNodeI(nkAsgn, n.info)
asgn.add(ctx.newUnrollFinallyAccess(n.info))
asgn.add(newIntTypeNode(nkIntLit, 1, ctx.g.getSysType(n.info, tyBool)))
result.add(asgn)
if n[0].kind != nkEmpty:
let asgnTmpResult = newNodeI(nkAsgn, n.info)
asgnTmpResult.add(ctx.newTmpResultAccess())
asgnTmpResult.add(n[0])
result.add(asgnTmpResult)
result.add(ctx.newNullifyCurExc(n.info))
let goto = newTree(nkGotoState, ctx.g.newIntLit(n.info, ctx.nearestFinally))
result.add(goto)
of nkSkip:
discard
else:
for i in 0 ..< n.len:
n[i] = ctx.transformReturnsInTry(n[i])
proc transformClosureIteratorBody(ctx: var Ctx, n: PNode, gotoOut: PNode): PNode =
result = n
case n.kind:
of nkSkip:
discard
of nkStmtList, nkStmtListExpr:
result = addGotoOut(result, gotoOut)
for i in 0 ..< n.len:
if n[i].hasYields:
# Create a new split
let go = newNodeI(nkGotoState, n[i].info)
n[i] = ctx.transformClosureIteratorBody(n[i], go)
let s = newNodeI(nkStmtList, n[i + 1].info)
for j in i + 1 ..< n.len:
s.add(n[j])
n.sons.setLen(i + 1)
discard ctx.newState(s, go)
if ctx.transformClosureIteratorBody(s, gotoOut) != s:
internalError(ctx.g.config, "transformClosureIteratorBody != s")
break
of nkYieldStmt:
result = newNodeI(nkStmtList, n.info)
result.add(n)
result.add(gotoOut)
of nkElse, nkElseExpr:
result[0] = addGotoOut(result[0], gotoOut)
result[0] = ctx.transformClosureIteratorBody(result[0], gotoOut)
of nkElifBranch, nkElifExpr, nkOfBranch:
result[^1] = addGotoOut(result[^1], gotoOut)
result[^1] = ctx.transformClosureIteratorBody(result[^1], gotoOut)
of nkIfStmt, nkCaseStmt:
for i in 0 ..< n.len:
n[i] = ctx.transformClosureIteratorBody(n[i], gotoOut)
if n[^1].kind != nkElse:
# We don't have an else branch, but every possible branch has to end with
# gotoOut, so add else here.
let elseBranch = newTree(nkElse, gotoOut)
n.add(elseBranch)
of nkWhileStmt:
# while e:
# s
# ->
# BEGIN_STATE:
# if e:
# s
# goto BEGIN_STATE
# else:
# goto OUT
result = newNodeI(nkGotoState, n.info)
let s = newNodeI(nkStmtList, n.info)
discard ctx.newState(s, result)
let ifNode = newNodeI(nkIfStmt, n.info)
let elifBranch = newNodeI(nkElifBranch, n.info)
elifBranch.add(n[0])
var body = addGotoOut(n[1], result)
body = ctx.transformBreaksAndContinuesInWhile(body, result, gotoOut)
body = ctx.transformClosureIteratorBody(body, result)
elifBranch.add(body)
ifNode.add(elifBranch)
let elseBranch = newTree(nkElse, gotoOut)
ifNode.add(elseBranch)
s.add(ifNode)
of nkBlockStmt:
result[1] = addGotoOut(result[1], gotoOut)
result[1] = ctx.transformBreaksInBlock(result[1], result[0], gotoOut)
result[1] = ctx.transformClosureIteratorBody(result[1], gotoOut)
of nkTryStmt:
# See explanation above about how this works
ctx.hasExceptions = true
result = newNodeI(nkGotoState, n.info)
var tryBody = toStmtList(n[0])
var exceptBody = ctx.collectExceptState(n)
var finallyBody = newTree(nkStmtList, getFinallyNode(ctx, n))
finallyBody = ctx.transformReturnsInTry(finallyBody)
finallyBody.add(ctx.newEndFinallyNode(finallyBody.info))
# The following index calculation is based on the knowledge how state
# indexes are assigned
let tryIdx = ctx.states.len
var exceptIdx, finallyIdx: int
if exceptBody.kind != nkEmpty:
exceptIdx = -(tryIdx + 1)
finallyIdx = tryIdx + 2
else:
exceptIdx = tryIdx + 1
finallyIdx = tryIdx + 1
let outToFinally = newNodeI(nkGotoState, finallyBody.info)
block: # Create initial states.
let oldExcHandlingState = ctx.curExcHandlingState
ctx.curExcHandlingState = exceptIdx
let realTryIdx = ctx.newState(tryBody, result)
assert(realTryIdx == tryIdx)
if exceptBody.kind != nkEmpty:
ctx.curExcHandlingState = finallyIdx
let realExceptIdx = ctx.newState(exceptBody, nil)
assert(realExceptIdx == -exceptIdx)
ctx.curExcHandlingState = oldExcHandlingState
let realFinallyIdx = ctx.newState(finallyBody, outToFinally)
assert(realFinallyIdx == finallyIdx)
block: # Subdivide the states
let oldNearestFinally = ctx.nearestFinally
ctx.nearestFinally = finallyIdx
let oldExcHandlingState = ctx.curExcHandlingState
ctx.curExcHandlingState = exceptIdx
if ctx.transformReturnsInTry(tryBody) != tryBody:
internalError(ctx.g.config, "transformReturnsInTry != tryBody")
if ctx.transformClosureIteratorBody(tryBody, outToFinally) != tryBody:
internalError(ctx.g.config, "transformClosureIteratorBody != tryBody")
ctx.curExcHandlingState = finallyIdx
ctx.addElseToExcept(exceptBody)
if ctx.transformReturnsInTry(exceptBody) != exceptBody:
internalError(ctx.g.config, "transformReturnsInTry != exceptBody")
if ctx.transformClosureIteratorBody(exceptBody, outToFinally) != exceptBody:
internalError(ctx.g.config, "transformClosureIteratorBody != exceptBody")
ctx.curExcHandlingState = oldExcHandlingState
ctx.nearestFinally = oldNearestFinally
if ctx.transformClosureIteratorBody(finallyBody, gotoOut) != finallyBody:
internalError(ctx.g.config, "transformClosureIteratorBody != finallyBody")
of nkGotoState, nkForStmt:
internalError(ctx.g.config, "closure iter " & $n.kind)
else:
for i in 0 ..< n.len:
n[i] = ctx.transformClosureIteratorBody(n[i], gotoOut)
proc stateFromGotoState(n: PNode): int =
assert(n.kind == nkGotoState)
result = n[0].intVal.int
proc transformStateAssignments(ctx: var Ctx, n: PNode): PNode =
# This transforms 3 patterns:
########################## 1
# yield e
# goto STATE
# ->
# :state = STATE
# return e
########################## 2
# goto STATE
# ->
# :state = STATE
# break :stateLoop
########################## 3
# return e
# ->
# :state = -1
# return e
#
result = n
case n.kind
of nkStmtList, nkStmtListExpr:
if n.len != 0 and n[0].kind == nkYieldStmt:
assert(n.len == 2)
assert(n[1].kind == nkGotoState)
result = newNodeI(nkStmtList, n.info)
result.add(ctx.newStateAssgn(stateFromGotoState(n[1])))
var retStmt = newNodeI(nkReturnStmt, n.info)
if n[0].sons[0].kind != nkEmpty:
var a = newNodeI(nkAsgn, n[0].sons[0].info)
var retVal = n[0].sons[0] #liftCapturedVars(n.sons[0], owner, d, c)
addSon(a, newSymNode(getClosureIterResult(ctx.g, ctx.fn)))
addSon(a, retVal)
retStmt.add(a)
else:
retStmt.add(ctx.g.emptyNode)
result.add(retStmt)
else:
for i in 0 ..< n.len:
n[i] = ctx.transformStateAssignments(n[i])
of nkSkip:
discard
of nkReturnStmt:
result = newNodeI(nkStmtList, n.info)
result.add(ctx.newStateAssgn(-1))
result.add(n)
of nkGotoState:
result = newNodeI(nkStmtList, n.info)
result.add(ctx.newStateAssgn(stateFromGotoState(n)))
let breakState = newNodeI(nkBreakStmt, n.info)
breakState.add(newSymNode(ctx.stateLoopLabel))
result.add(breakState)
else:
for i in 0 ..< n.len:
n[i] = ctx.transformStateAssignments(n[i])
proc skipStmtList(ctx: Ctx; n: PNode): PNode =
result = n
while result.kind in {nkStmtList}:
if result.len == 0: return ctx.g.emptyNode
result = result[0]
proc skipEmptyStates(ctx: Ctx, stateIdx: int): int =
# Returns first non-empty state idx for `stateIdx`. Returns `stateIdx` if
# it is not empty
var maxJumps = ctx.states.len # maxJumps used only for debugging purposes.
var stateIdx = stateIdx
while true:
let label = stateIdx
if label == ctx.exitStateIdx: break
var newLabel = label
if label == -1:
newLabel = ctx.exitStateIdx
else:
let fs = skipStmtList(ctx, ctx.states[label][1])
if fs.kind == nkGotoState:
newLabel = fs[0].intVal.int
if label == newLabel: break
stateIdx = newLabel
dec maxJumps
if maxJumps == 0:
assert(false, "Internal error")
result = ctx.states[stateIdx][0].intVal.int
proc skipThroughEmptyStates(ctx: var Ctx, n: PNode): PNode =
result = n
case n.kind
of nkSkip:
discard
of nkGotoState:
result = copyTree(n)
result[0].intVal = ctx.skipEmptyStates(result[0].intVal.int)
else:
for i in 0 ..< n.len:
n[i] = ctx.skipThroughEmptyStates(n[i])
proc newArrayType(g: ModuleGraph; n: int, t: PType, owner: PSym): PType =
result = newType(tyArray, owner)
let rng = newType(tyRange, owner)
rng.n = newTree(nkRange, g.newIntLit(owner.info, 0), g.newIntLit(owner.info, n))
rng.rawAddSon(t)
result.rawAddSon(rng)
result.rawAddSon(t)
proc createExceptionTable(ctx: var Ctx): PNode {.inline.} =
result = newNodeI(nkBracket, ctx.fn.info)
result.typ = ctx.g.newArrayType(ctx.exceptionTable.len, ctx.g.getSysType(ctx.fn.info, tyInt16), ctx.fn)
for i in ctx.exceptionTable:
let elem = newIntNode(nkIntLit, i)
elem.typ = ctx.g.getSysType(ctx.fn.info, tyInt16)
result.add(elem)
proc newCatchBody(ctx: var Ctx, info: TLineInfo): PNode {.inline.} =
# Generates the code:
# :state = exceptionTable[:state]
# if :state == 0: raise
# :unrollFinally = :state > 0
# if :state < 0:
# :state = -:state
# :curExc = getCurrentException()
result = newNodeI(nkStmtList, info)
let intTyp = ctx.g.getSysType(info, tyInt)
let boolTyp = ctx.g.getSysType(info, tyBool)
# :state = exceptionTable[:state]
block:
# exceptionTable[:state]
let getNextState = newTree(nkBracketExpr,
ctx.createExceptionTable(),
ctx.newStateAccess())
getNextState.typ = intTyp
# :state = exceptionTable[:state]
result.add(ctx.newStateAssgn(getNextState))
# if :state == 0: raise
block:
let cond = newTree(nkCall,
ctx.g.getSysMagic(info, "==", mEqI).newSymNode(),
ctx.newStateAccess(),
newIntTypeNode(nkIntLit, 0, intTyp))
cond.typ = boolTyp
let raiseStmt = newTree(nkRaiseStmt, ctx.g.emptyNode)
let ifBranch = newTree(nkElifBranch, cond, raiseStmt)
let ifStmt = newTree(nkIfStmt, ifBranch)
result.add(ifStmt)
# :unrollFinally = :state > 0
block:
let cond = newTree(nkCall,
ctx.g.getSysMagic(info, "<", mLtI).newSymNode,
newIntTypeNode(nkIntLit, 0, intTyp),
ctx.newStateAccess())
cond.typ = boolTyp
let asgn = newTree(nkAsgn, ctx.newUnrollFinallyAccess(info), cond)
result.add(asgn)
# if :state < 0: :state = -:state
block:
let cond = newTree(nkCall,
ctx.g.getSysMagic(info, "<", mLtI).newSymNode,
ctx.newStateAccess(),
newIntTypeNode(nkIntLit, 0, intTyp))
cond.typ = boolTyp
let negateState = newTree(nkCall,
ctx.g.getSysMagic(info, "-", mUnaryMinusI).newSymNode,
ctx.newStateAccess())
negateState.typ = intTyp
let ifBranch = newTree(nkElifBranch, cond, ctx.newStateAssgn(negateState))
let ifStmt = newTree(nkIfStmt, ifBranch)
result.add(ifStmt)
# :curExc = getCurrentException()
block:
result.add(newTree(nkAsgn,
ctx.newCurExcAccess(),
ctx.g.callCodegenProc("getCurrentException", ctx.g.emptyNode)))
proc wrapIntoTryExcept(ctx: var Ctx, n: PNode): PNode {.inline.} =
let setupExc = newTree(nkCall,
newSymNode(ctx.g.getCompilerProc("closureIterSetupExc")),
ctx.newCurExcAccess())
let tryBody = newTree(nkStmtList, setupExc, n)
let exceptBranch = newTree(nkExceptBranch, ctx.newCatchBody(ctx.fn.info))
result = newTree(nkTryStmt, tryBody, exceptBranch)
proc wrapIntoStateLoop(ctx: var Ctx, n: PNode): PNode =
# while true:
# block :stateLoop:
# gotoState :state
# local vars decl (if needed)
# body # Might get wrapped in try-except
let loopBody = newNodeI(nkStmtList, n.info)
result = newTree(nkWhileStmt, newSymNode(ctx.g.getSysSym(n.info, "true")), loopBody)
result.info = n.info
let localVars = newNodeI(nkStmtList, n.info)
if not ctx.stateVarSym.isNil:
let varSect = newNodeI(nkVarSection, n.info)
addVar(varSect, newSymNode(ctx.stateVarSym))
localVars.add(varSect)
if not ctx.tempVars.isNil:
localVars.add(ctx.tempVars)
let blockStmt = newNodeI(nkBlockStmt, n.info)
blockStmt.add(newSymNode(ctx.stateLoopLabel))
let gs = newNodeI(nkGotoState, n.info)
gs.add(ctx.newStateAccess())
gs.add(ctx.g.newIntLit(n.info, ctx.states.len - 1))
var blockBody = newTree(nkStmtList, gs, localVars, n)
if ctx.hasExceptions:
blockBody = ctx.wrapIntoTryExcept(blockBody)
blockStmt.add(blockBody)
loopBody.add(blockStmt)
proc deleteEmptyStates(ctx: var Ctx) =
let goOut = newTree(nkGotoState, ctx.g.newIntLit(TLineInfo(), -1))
ctx.exitStateIdx = ctx.newState(goOut, nil)
# Apply new state indexes and mark unused states with -1
var iValid = 0
for i, s in ctx.states:
let body = skipStmtList(ctx, s[1])
if body.kind == nkGotoState and i != ctx.states.len - 1 and i != 0:
# This is an empty state. Mark with -1.
s[0].intVal = -1
else:
s[0].intVal = iValid
inc iValid
for i, s in ctx.states:
let body = skipStmtList(ctx, s[1])
if body.kind != nkGotoState or i == 0:
discard ctx.skipThroughEmptyStates(s)
let excHandlState = ctx.exceptionTable[i]
if excHandlState < 0:
ctx.exceptionTable[i] = -ctx.skipEmptyStates(-excHandlState)
elif excHandlState != 0:
ctx.exceptionTable[i] = ctx.skipEmptyStates(excHandlState)
var i = 0
while i < ctx.states.len - 1:
let fs = skipStmtList(ctx, ctx.states[i][1])
if fs.kind == nkGotoState and i != 0:
ctx.states.delete(i)
ctx.exceptionTable.delete(i)
else:
inc i
proc transformClosureIterator*(g: ModuleGraph; fn: PSym, n: PNode): PNode =
var ctx: Ctx
ctx.g = g
ctx.fn = fn
if getEnvParam(fn).isNil:
# Lambda lifting was not done yet. Use temporary :state sym, which
# be handled specially by lambda lifting. Local temp vars (if needed)
# should folllow the same logic.
ctx.stateVarSym = newSym(skVar, getIdent(ctx.g.cache, ":state"), fn, fn.info)
ctx.stateVarSym.typ = g.createClosureIterStateType(fn)
ctx.stateLoopLabel = newSym(skLabel, getIdent(ctx.g.cache, ":stateLoop"), fn, fn.info)
var n = n.toStmtList
discard ctx.newState(n, nil)
let gotoOut = newTree(nkGotoState, g.newIntLit(n.info, -1))
var ns = false
n = ctx.lowerStmtListExprs(n, ns)
if n.hasYieldsInExpressions():
internalError(ctx.g.config, "yield in expr not lowered")
# Splitting transformation
discard ctx.transformClosureIteratorBody(n, gotoOut)
# Optimize empty states away
ctx.deleteEmptyStates()
# Make new body by concating the list of states
result = newNodeI(nkStmtList, n.info)
for s in ctx.states:
assert(s.len == 2)
let body = s[1]
s.sons.del(1)
result.add(s)
result.add(body)
result = ctx.transformStateAssignments(result)
result = ctx.wrapIntoStateLoop(result)
# echo "TRANSFORM TO STATES: "
# echo renderTree(result)
# echo "exception table:"
# for i, e in ctx.exceptionTable:
# echo i, " -> ", e
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