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ORC: prepare for another patent-pending optimization (#15996)

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* ORC: prepare for another patent-pending optimization

* bugfix

* '=copy' for refs can take a cyclic parameter for more ORC optimizations

* ORC: exploit the common 'it = it.next' pattern

* can't hurt to check for nil

* use an algorithm that is not obviously broken

* restore the test case

* final cleanups for --gc:orc
This commit is contained in:
Andreas Rumpf 2020-11-18 22:31:06 +01:00 • committed by GitHub
commit b9eb91cbb5
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7 changed files with 147 additions and 39 deletions
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49
compiler/injectdestructors.nim
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@ -311,6 +311,43 @@ proc genSink(c: var Con; dest, ri: PNode, isDecl = false): PNode =
# and copyMem(dest, source). This is efficient.
result = newTree(nkStmtList, c.genDestroy(dest), newTree(nkFastAsgn, dest, ri))
proc isCriticalLink(dest: PNode): bool {.inline.} =
#[
Lins's idea that only "critical" links can introduce a cycle. This is
critical for the performance gurantees that we strive for: If you
traverse a data structure, no tracing will be performed at all.
ORC is about this promise: The GC only touches the memory that the
mutator touches too.
These constructs cannot possibly create cycles::
local = ...
new(x)
dest = ObjectConstructor(field: noalias(dest))
But since 'ObjectConstructor' is already moved into 'dest' all we really have
to look for is assignments to local variables.
]#
result = dest.kind != nkSym
proc finishCopy(c: var Con; result, dest: PNode; isFromSink: bool) =
if c.graph.config.selectedGC == gcOrc:
let t = dest.typ.skipTypes({tyGenericInst, tyAlias, tySink, tyDistinct})
if cyclicType(t):
result.add boolLit(c.graph, result.info, isFromSink or isCriticalLink(dest))
proc genMarkCyclic(c: var Con; result, dest: PNode) =
if c.graph.config.selectedGC == gcOrc:
let t = dest.typ.skipTypes({tyGenericInst, tyAlias, tySink, tyDistinct})
if cyclicType(t):
if t.kind == tyRef:
result.add callCodegenProc(c.graph, "nimMarkCyclic", dest.info, dest)
else:
let xenv = genBuiltin(c.graph, mAccessEnv, "accessEnv", dest)
xenv.typ = getSysType(c.graph, dest.info, tyPointer)
result.add callCodegenProc(c.graph, "nimMarkCyclic", dest.info, xenv)
proc genCopyNoCheck(c: var Con; dest, ri: PNode): PNode =
let t = dest.typ.skipTypes({tyGenericInst, tyAlias, tySink})
result = c.genOp(t, attachedAsgn, dest, ri)
@ -390,7 +427,9 @@ proc destructiveMoveVar(n: PNode; c: var Con; s: var Scope): PNode =
v.add(vpart)
result.add v
let wasMovedCall = c.genWasMoved(skipConv(n))
let nn = skipConv(n)
c.genMarkCyclic(result, nn)
let wasMovedCall = c.genWasMoved(nn)
result.add wasMovedCall
result.add tempAsNode
@ -405,6 +444,7 @@ proc passCopyToSink(n: PNode; c: var Con; s: var Scope): PNode =
result.add c.genWasMoved(tmp)
var m = c.genCopy(tmp, n)
m.add p(n, c, s, normal)
c.finishCopy(m, n, isFromSink = true)
result.add m
if isLValue(n) and not isCapturedVar(n) and n.typ.skipTypes(abstractInst).kind != tyRef and c.inSpawn == 0:
message(c.graph.config, n.info, hintPerformance,
@ -667,6 +707,7 @@ proc pRaiseStmt(n: PNode, c: var Con; s: var Scope): PNode =
let tmp = c.getTemp(s, n[0].typ, n.info)
var m = c.genCopyNoCheck(tmp, n[0])
m.add p(n[0], c, s, normal)
c.finishCopy(m, n[0], isFromSink = false)
result = newTree(nkStmtList, c.genWasMoved(tmp), m)
var toDisarm = n[0]
if toDisarm.kind == nkStmtListExpr: toDisarm = toDisarm.lastSon
@ -941,16 +982,18 @@ proc moveOrCopy(dest, ri: PNode; c: var Con; s: var Scope, isDecl = false): PNod
else:
result = c.genCopy(dest, ri)
result.add p(ri, c, s, consumed)
c.finishCopy(result, dest, isFromSink = false)
of nkBracket:
# array constructor
if ri.len > 0 and isDangerousSeq(ri.typ):
result = c.genCopy(dest, ri)
result.add p(ri, c, s, consumed)
c.finishCopy(result, dest, isFromSink = false)
else:
result = c.genSink(dest, p(ri, c, s, consumed), isDecl)
of nkObjConstr, nkTupleConstr, nkClosure, nkCharLit..nkNilLit:
result = c.genSink(dest, p(ri, c, s, consumed), isDecl)
of nkSym:
of nkSym:
if dest.kind == nkSym and dest.sym == ri.sym:
# rule (self-assignment-removal):
result = newNodeI(nkEmpty, dest.info)
@ -966,6 +1009,7 @@ proc moveOrCopy(dest, ri: PNode; c: var Con; s: var Scope, isDecl = false): PNod
else:
result = c.genCopy(dest, ri)
result.add p(ri, c, s, consumed)
c.finishCopy(result, dest, isFromSink = false)
of nkHiddenSubConv, nkHiddenStdConv, nkConv, nkObjDownConv, nkObjUpConv:
result = c.genSink(dest, p(ri, c, s, sinkArg), isDecl)
of nkStmtListExpr, nkBlockExpr, nkIfExpr, nkCaseStmt, nkTryStmt:
@ -983,6 +1027,7 @@ proc moveOrCopy(dest, ri: PNode; c: var Con; s: var Scope, isDecl = false): PNod
else:
result = c.genCopy(dest, ri)
result.add p(ri, c, s, consumed)
c.finishCopy(result, dest, isFromSink = false)
proc computeUninit(c: var Con) =
if not c.uninitComputed: