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Automatic tail-call optimization (auto-TCO) in StaticOptimizer #694

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80 changes: 59 additions & 21 deletions sjsonnet/src/sjsonnet/Evaluator.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -501,11 +501,18 @@ class Evaluator(
checkStackDepth(e.pos, e)
try {
val lhs = visitExpr(e.value)
// Auto-TCO'd calls should normally be intercepted by visitExprWithTailCallSupport,
// but we handle them defensively here to preserve lazy semantics if this path is ever reached.
implicit val tailstrictMode: TailstrictMode =
if (e.tailstrict) TailstrictModeEnabled else TailstrictModeDisabled
if (e.isAutoTCO) TailstrictModeAutoTCO
else if (e.tailstrict) TailstrictModeEnabled
else TailstrictModeDisabled

if (e.tailstrict) {
TailCall.resolve(lhs.cast[Val.Func].apply(e.args.map(visitExpr(_)), e.namedNames, e.pos))
val args: Array[Eval] =
if (e.isAutoTCO) e.args.map(visitAsLazy(_))
else e.args.map(visitExpr(_)).asInstanceOf[Array[Eval]]
TailCall.resolve(lhs.cast[Val.Func].apply(args, e.namedNames, e.pos))
} else {
lhs.cast[Val.Func].apply(e.args.map(visitAsLazy(_)), e.namedNames, e.pos)
}
Expand All @@ -518,7 +525,9 @@ class Evaluator(
try {
val lhs = visitExpr(e.value)
implicit val tailstrictMode: TailstrictMode =
if (e.tailstrict) TailstrictModeEnabled else TailstrictModeDisabled
if (e.isAutoTCO) TailstrictModeAutoTCO
else if (e.tailstrict) TailstrictModeEnabled
else TailstrictModeDisabled
if (e.tailstrict) {
TailCall.resolve(lhs.cast[Val.Func].apply0(e.pos))
} else {
Expand All @@ -533,9 +542,12 @@ class Evaluator(
try {
val lhs = visitExpr(e.value)
implicit val tailstrictMode: TailstrictMode =
if (e.tailstrict) TailstrictModeEnabled else TailstrictModeDisabled
if (e.isAutoTCO) TailstrictModeAutoTCO
else if (e.tailstrict) TailstrictModeEnabled
else TailstrictModeDisabled
if (e.tailstrict) {
TailCall.resolve(lhs.cast[Val.Func].apply1(visitExpr(e.a1), e.pos))
val arg: Eval = if (e.isAutoTCO) visitAsLazy(e.a1) else visitExpr(e.a1)
TailCall.resolve(lhs.cast[Val.Func].apply1(arg, e.pos))
} else {
val l1 = visitAsLazy(e.a1)
lhs.cast[Val.Func].apply1(l1, e.pos)
Expand All @@ -549,10 +561,18 @@ class Evaluator(
try {
val lhs = visitExpr(e.value)
implicit val tailstrictMode: TailstrictMode =
if (e.tailstrict) TailstrictModeEnabled else TailstrictModeDisabled
if (e.isAutoTCO) TailstrictModeAutoTCO
else if (e.tailstrict) TailstrictModeEnabled
else TailstrictModeDisabled

if (e.tailstrict) {
TailCall.resolve(lhs.cast[Val.Func].apply2(visitExpr(e.a1), visitExpr(e.a2), e.pos))
if (e.isAutoTCO) {
TailCall.resolve(
lhs.cast[Val.Func].apply2(visitAsLazy(e.a1), visitAsLazy(e.a2), e.pos)
)
} else {
TailCall.resolve(lhs.cast[Val.Func].apply2(visitExpr(e.a1), visitExpr(e.a2), e.pos))
}
} else {
val l1 = visitAsLazy(e.a1)
val l2 = visitAsLazy(e.a2)
Expand All @@ -567,12 +587,22 @@ class Evaluator(
try {
val lhs = visitExpr(e.value)
implicit val tailstrictMode: TailstrictMode =
if (e.tailstrict) TailstrictModeEnabled else TailstrictModeDisabled
if (e.isAutoTCO) TailstrictModeAutoTCO
else if (e.tailstrict) TailstrictModeEnabled
else TailstrictModeDisabled

if (e.tailstrict) {
TailCall.resolve(
lhs.cast[Val.Func].apply3(visitExpr(e.a1), visitExpr(e.a2), visitExpr(e.a3), e.pos)
)
if (e.isAutoTCO) {
TailCall.resolve(
lhs
.cast[Val.Func]
.apply3(visitAsLazy(e.a1), visitAsLazy(e.a2), visitAsLazy(e.a3), e.pos)
)
} else {
TailCall.resolve(
lhs.cast[Val.Func].apply3(visitExpr(e.a1), visitExpr(e.a2), visitExpr(e.a3), e.pos)
)
}
} else {
val l1 = visitAsLazy(e.a1)
val l2 = visitAsLazy(e.a2)
Expand Down Expand Up @@ -1104,32 +1134,40 @@ class Evaluator(
case e: Apply =>
try {
val func = visitExpr(e.value).cast[Val.Func]
new TailCall(func, e.args.map(visitExpr(_)).asInstanceOf[Array[Eval]], e.namedNames, e)
val isAuto = e.isAutoTCO
val args: Array[Eval] =
if (isAuto) e.args.map(visitAsLazy(_))
else e.args.map(visitExpr(_)).asInstanceOf[Array[Eval]]
new TailCall(func, args, e.namedNames, e, autoTCO = isAuto)
} catch Error.withStackFrame(e)
case e: Apply0 =>
try {
val func = visitExpr(e.value).cast[Val.Func]
new TailCall(func, Evaluator.emptyLazyArray, null, e)
new TailCall(func, Evaluator.emptyLazyArray, null, e, autoTCO = e.isAutoTCO)
} catch Error.withStackFrame(e)
case e: Apply1 =>
try {
val func = visitExpr(e.value).cast[Val.Func]
new TailCall(func, Array[Eval](visitExpr(e.a1)), null, e)
val isAuto = e.isAutoTCO
val arg: Eval = if (isAuto) visitAsLazy(e.a1) else visitExpr(e.a1)
new TailCall(func, Array[Eval](arg), null, e, autoTCO = isAuto)
} catch Error.withStackFrame(e)
case e: Apply2 =>
try {
val func = visitExpr(e.value).cast[Val.Func]
new TailCall(func, Array[Eval](visitExpr(e.a1), visitExpr(e.a2)), null, e)
val isAuto = e.isAutoTCO
val a1: Eval = if (isAuto) visitAsLazy(e.a1) else visitExpr(e.a1)
val a2: Eval = if (isAuto) visitAsLazy(e.a2) else visitExpr(e.a2)
new TailCall(func, Array[Eval](a1, a2), null, e, autoTCO = isAuto)
} catch Error.withStackFrame(e)
case e: Apply3 =>
try {
val func = visitExpr(e.value).cast[Val.Func]
new TailCall(
func,
Array[Eval](visitExpr(e.a1), visitExpr(e.a2), visitExpr(e.a3)),
null,
e
)
val isAuto = e.isAutoTCO
val a1: Eval = if (isAuto) visitAsLazy(e.a1) else visitExpr(e.a1)
val a2: Eval = if (isAuto) visitAsLazy(e.a2) else visitExpr(e.a2)
val a3: Eval = if (isAuto) visitAsLazy(e.a3) else visitExpr(e.a3)
new TailCall(func, Array[Eval](a1, a2, a3), null, e, autoTCO = isAuto)
} catch Error.withStackFrame(e)
case _ => visitExpr(e)
}
Expand Down
40 changes: 35 additions & 5 deletions sjsonnet/src/sjsonnet/Expr.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -52,6 +52,14 @@ trait Expr {
*/
trait TailstrictableExpr extends Expr {
def tailstrict: Boolean

/**
* True when this call was auto-TCO'd by the StaticOptimizer (as opposed to an explicit
* `tailstrict` annotation by the user). Auto-TCO'd calls use lazy argument evaluation to preserve
* Jsonnet's standard lazy semantics, whereas explicit `tailstrict` forces eager argument
* evaluation per the Jsonnet spec.
*/
def isAutoTCO: Boolean = false
}

object Expr {
Expand Down Expand Up @@ -231,36 +239,58 @@ object Expr {
value: Expr,
args: Array[Expr],
namedNames: Array[String],
tailstrict: Boolean)
tailstrict: Boolean,
autoTCO: Boolean = false)
extends TailstrictableExpr {
final override private[sjsonnet] def tag = ExprTags.Apply
override def exprErrorString: String = Expr.callTargetName(value)
override def isAutoTCO: Boolean = autoTCO
}
final case class Apply0(var pos: Position, value: Expr, tailstrict: Boolean)
final case class Apply0(
var pos: Position,
value: Expr,
tailstrict: Boolean,
autoTCO: Boolean = false)
extends TailstrictableExpr {
final override private[sjsonnet] def tag = ExprTags.Apply0
override def exprErrorString: String = Expr.callTargetName(value)
override def isAutoTCO: Boolean = autoTCO
}
final case class Apply1(var pos: Position, value: Expr, a1: Expr, tailstrict: Boolean)
final case class Apply1(
var pos: Position,
value: Expr,
a1: Expr,
tailstrict: Boolean,
autoTCO: Boolean = false)
extends TailstrictableExpr {
final override private[sjsonnet] def tag = ExprTags.Apply1
override def exprErrorString: String = Expr.callTargetName(value)
override def isAutoTCO: Boolean = autoTCO
}
final case class Apply2(var pos: Position, value: Expr, a1: Expr, a2: Expr, tailstrict: Boolean)
final case class Apply2(
var pos: Position,
value: Expr,
a1: Expr,
a2: Expr,
tailstrict: Boolean,
autoTCO: Boolean = false)
extends TailstrictableExpr {
final override private[sjsonnet] def tag = ExprTags.Apply2
override def exprErrorString: String = Expr.callTargetName(value)
override def isAutoTCO: Boolean = autoTCO
}
final case class Apply3(
var pos: Position,
value: Expr,
a1: Expr,
a2: Expr,
a3: Expr,
tailstrict: Boolean)
tailstrict: Boolean,
autoTCO: Boolean = false)
extends TailstrictableExpr {
final override private[sjsonnet] def tag = ExprTags.Apply3
override def exprErrorString: String = Expr.callTargetName(value)
override def isAutoTCO: Boolean = autoTCO
}
final case class ApplyBuiltin(
var pos: Position,
Expand Down
20 changes: 10 additions & 10 deletions sjsonnet/src/sjsonnet/ExprTransform.scala
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Expand Up @@ -14,37 +14,37 @@ abstract class ExprTransform {
if (x2 eq x) expr
else Select(pos, x2, name)

case Apply(pos, x, y, namedNames, tailstrict) =>
case Apply(pos, x, y, namedNames, tailstrict, autoTCO) =>
val x2 = transform(x)
val y2 = transformArr(y)
if ((x2 eq x) && (y2 eq y)) expr
else Apply(pos, x2, y2, namedNames, tailstrict)
else Apply(pos, x2, y2, namedNames, tailstrict, autoTCO)

case Apply0(pos, x, tailstrict) =>
case Apply0(pos, x, tailstrict, autoTCO) =>
val x2 = transform(x)
if (x2 eq x) expr
else Apply0(pos, x2, tailstrict)
else Apply0(pos, x2, tailstrict, autoTCO)

case Apply1(pos, x, y, tailstrict) =>
case Apply1(pos, x, y, tailstrict, autoTCO) =>
val x2 = transform(x)
val y2 = transform(y)
if ((x2 eq x) && (y2 eq y)) expr
else Apply1(pos, x2, y2, tailstrict)
else Apply1(pos, x2, y2, tailstrict, autoTCO)

case Apply2(pos, x, y, z, tailstrict) =>
case Apply2(pos, x, y, z, tailstrict, autoTCO) =>
val x2 = transform(x)
val y2 = transform(y)
val z2 = transform(z)
if ((x2 eq x) && (y2 eq y) && (z2 eq z)) expr
else Apply2(pos, x2, y2, z2, tailstrict)
else Apply2(pos, x2, y2, z2, tailstrict, autoTCO)

case Apply3(pos, x, y, z, a, tailstrict) =>
case Apply3(pos, x, y, z, a, tailstrict, autoTCO) =>
val x2 = transform(x)
val y2 = transform(y)
val z2 = transform(z)
val a2 = transform(a)
if ((x2 eq x) && (y2 eq y) && (z2 eq z) && (a2 eq a)) expr
else Apply3(pos, x2, y2, z2, a2, tailstrict)
else Apply3(pos, x2, y2, z2, a2, tailstrict, autoTCO)

case ApplyBuiltin(pos, func, x, tailstrict) =>
val x2 = transformArr(x)
Expand Down
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