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An optimizer for ARC (#14962)

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* WIP: an optimizer for ARC
* do not optimize away destructors in 'finally' if unstructured control flow is involved
* optimized the optimizer
* minor code cleanup
* first steps to .cursor inference
* cursor inference: big steps to a working solution
* baby steps
* better .cursor inference
* new feature: expandArc for easy inspection of the AST after ARC transformations
* added topt_cursor test
* adapt tests
* cleanups, make tests green
* optimize common traversal patterns
* moved test case
* fixes .cursor inference so that npeg compiles once again
* cursor inference: more bugfixes

Co-authored-by: Clyybber <darkmine956@gmail.com>
This commit is contained in:
Andreas Rumpf 2020-07-15 23:00:06 +02:00 • committed by GitHub
commit c5358b0d4b
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19 changed files with 895 additions and 62 deletions
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54
compiler/injectdestructors.nim
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@ -13,18 +13,11 @@
## See doc/destructors.rst for a spec of the implemented rewrite rules
## XXX Optimization to implement: if a local variable is only assigned
## string literals as in ``let x = conf: "foo" else: "bar"`` do not
## produce a destructor call for ``x``. The address of ``x`` must also
## not have been taken. ``x = "abc"; x.add(...)``
# Todo:
# - eliminate 'wasMoved(x); destroy(x)' pairs as a post processing step.
import
intsets, ast, astalgo, msgs, renderer, magicsys, types, idents,
intsets, strtabs, ast, astalgo, msgs, renderer, magicsys, types, idents,
strutils, options, dfa, lowerings, tables, modulegraphs, msgs,
lineinfos, parampatterns, sighashes, liftdestructors
lineinfos, parampatterns, sighashes, liftdestructors, optimizer,
cursor_inference
from trees import exprStructuralEquivalent, getRoot
@ -42,6 +35,7 @@ type
Con = object
owner: PSym
g: ControlFlowGraph
cursors: IntSet
graph: ModuleGraph
otherRead: PNode
inLoop, inSpawn: int
@ -155,6 +149,17 @@ proc isLastRead(location: PNode; cfg: ControlFlowGraph; otherRead: var PNode; pc
pc = min(variantA, variantB)
return pc
proc isCursor(n: PNode; c: Con): bool =
case n.kind
of nkSym:
result = sfCursor in n.sym.flags or c.cursors.contains(n.sym.id)
of nkDotExpr:
result = sfCursor in n[1].sym.flags
of nkCheckedFieldExpr:
result = isCursor(n[0], c)
else:
result = false
proc isLastRead(n: PNode; c: var Con): bool =
# first we need to search for the instruction that belongs to 'n':
var instr = -1
@ -486,17 +491,6 @@ proc ensureDestruction(arg, orig: PNode; c: var Con; s: var Scope): PNode =
else:
result = arg
proc isCursor(n: PNode): bool =
case n.kind
of nkSym:
result = sfCursor in n.sym.flags
of nkDotExpr:
result = sfCursor in n[1].sym.flags
of nkCheckedFieldExpr:
result = isCursor(n[0])
else:
result = false
proc cycleCheck(n: PNode; c: var Con) =
if c.graph.config.selectedGC != gcArc: return
var value = n[1]
@ -727,7 +721,8 @@ proc p(n: PNode; c: var Con; s: var Scope; mode: ProcessMode): PNode =
elif n.kind in {nkBracket, nkObjConstr, nkTupleConstr, nkClosure, nkNilLit} +
nkCallKinds + nkLiterals:
result = p(n, c, s, consumed)
elif ((n.kind == nkSym and isSinkParam(n.sym)) or isAnalysableFieldAccess(n, c.owner)) and isLastRead(n, c):
elif ((n.kind == nkSym and isSinkParam(n.sym)) or isAnalysableFieldAccess(n, c.owner)) and
isLastRead(n, c) and not (n.kind == nkSym and isCursor(n, c)):
# Sinked params can be consumed only once. We need to reset the memory
# to disable the destructor which we have not elided
result = destructiveMoveVar(n, c, s)
@ -830,7 +825,7 @@ proc p(n: PNode; c: var Con; s: var Scope; mode: ProcessMode): PNode =
if it.kind == nkVarTuple and hasDestructor(ri.typ):
let x = lowerTupleUnpacking(c.graph, it, c.owner)
result.add p(x, c, s, consumed)
elif it.kind == nkIdentDefs and hasDestructor(it[0].typ) and not isCursor(it[0]):
elif it.kind == nkIdentDefs and hasDestructor(it[0].typ) and not isCursor(it[0], c):
for j in 0..<it.len-2:
let v = it[j]
if v.kind == nkSym:
@ -851,7 +846,7 @@ proc p(n: PNode; c: var Con; s: var Scope; mode: ProcessMode): PNode =
result.add v
of nkAsgn, nkFastAsgn:
if hasDestructor(n[0].typ) and n[1].kind notin {nkProcDef, nkDo, nkLambda} and
not isCursor(n[0]):
not isCursor(n[0], c):
# rule (self-assignment-removal):
if n[1].kind == nkSym and n[0].kind == nkSym and n[0].sym == n[1].sym:
result = newNodeI(nkEmpty, n.info)
@ -988,7 +983,7 @@ proc moveOrCopy(dest, ri: PNode; c: var Con; s: var Scope, isDecl = false): PNod
let snk = c.genSink(dest, ri, isDecl)
result = newTree(nkStmtList, snk, c.genWasMoved(ri))
elif ri.sym.kind != skParam and ri.sym.owner == c.owner and
isLastRead(ri, c) and canBeMoved(c, dest.typ):
isLastRead(ri, c) and canBeMoved(c, dest.typ) and not isCursor(ri, c):
# Rule 3: `=sink`(x, z); wasMoved(z)
let snk = c.genSink(dest, ri, isDecl)
result = newTree(nkStmtList, snk, c.genWasMoved(ri))
@ -1048,6 +1043,8 @@ proc injectDestructorCalls*(g: ModuleGraph; owner: PSym; n: PNode): PNode =
echoCfg(c.g)
echo n
c.cursors = computeCursors(n, g.config)
var scope: Scope
let body = p(n, c, scope, normal)
@ -1059,7 +1056,12 @@ proc injectDestructorCalls*(g: ModuleGraph; owner: PSym; n: PNode): PNode =
scope.final.add c.genDestroy(params[i])
#if optNimV2 in c.graph.config.globalOptions:
# injectDefaultCalls(n, c)
result = processScope(c, scope, body)
result = optimize processScope(c, scope, body)
dbg:
echo ">---------transformed-to--------->"
echo renderTree(result, {renderIds})
if g.config.arcToExpand.hasKey(owner.name.s):
echo "--expandArc: ", owner.name.s
echo renderTree(result, {renderIr})
echo "-- end of expandArc ------------------------"