speedy: short circuit precondition checking (digital-asset#12984)

* speedy: short circuit precondition checking Instead of evaluating all preconditions of templates and interfaces we evaluate preconditions one by one and throw an exception as soon as we find a failing one. This implemented via a lazy SBCheckPrecond builtin and a foldleft expression over the list of preconditions. CHANGELOG_BEGIN CHANGELOG_END * Update daml-lf/interpreter/src/main/scala/com/digitalasset/daml/lf/speedy/Compiler.scala Co-authored-by: Remy <remy.haemmerle@daml.com> * Update daml-lf/interpreter/src/main/scala/com/digitalasset/daml/lf/speedy/SBuiltin.scala Co-authored-by: Remy <remy.haemmerle@daml.com> * fix SUnit -> Unit * tests Co-authored-by: Remy <remy.haemmerle@daml.com>
kgeonw · Feb 22, 2022 · adaddde · adaddde
1 parent 942fbe0
commit adaddde
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Showing 4 changed files with 268 additions and 195 deletions.
diff --git a/daml-lf/interpreter/src/main/scala/com/digitalasset/daml/lf/speedy/Compiler.scala b/daml-lf/interpreter/src/main/scala/com/digitalasset/daml/lf/speedy/Compiler.scala
@@ -722,17 +722,15 @@ private[lf] final class Compiler(
       // `SBToInterface` is needed because interfaces do not have the same representation as the underlying template
       t.InterfacePrecondDefRef(impl._1)(SBToInterface(tmplId)(env2.toSEVar(tmplArgPos)))
     )
-    // TODO Clean this up as part of changing how we evaluate these
-    // https://github.com/digital-asset/daml/issues/11762
+
     val precondsArray: ImmArray[s.SExpr] =
-      (Iterator(translateExp(env2, tmpl.precond)) ++ implementsPrecondsIterator ++ Iterator(
-        s.SEValue.EmptyList
-      )).to(ImmArray)
-    val preconds = s.SEApp(s.SEBuiltin(SBConsMany(precondsArray.length - 1)), precondsArray.toList)
-    // We check precondition in a separated builtin to prevent
-    // further evaluation of agreement, signatories, observers and key
-    // in case of failed precondition.
-    let(env2, SBCheckPrecond(tmplId)(env2.toSEVar(tmplArgPos), preconds)) { (_, env) =>
+      (Iterator(translateExp(env2, tmpl.precond)) ++ implementsPrecondsIterator).to(ImmArray)
+
+    val preconds = precondsArray.foldLeft[s.SExpr](s.SEValue.Unit)((acc, precond) =>
+      SBCheckPrecond(tmplId)(env2.toSEVar(tmplArgPos), acc, precond)
+    )
+
+    let(env2, preconds) { (_, env) =>
       SBUCreate(tmplId, byInterface)(
         env.toSEVar(tmplArgPos),
         translateExp(env, tmpl.agreementText),

diff --git a/daml-lf/interpreter/src/main/scala/com/digitalasset/daml/lf/speedy/SBuiltin.scala b/daml-lf/interpreter/src/main/scala/com/digitalasset/daml/lf/speedy/SBuiltin.scala
@@ -72,6 +72,12 @@ private[speedy] sealed abstract class SBuiltin(val arity: Int) {
       case otherwise => unexpectedType(i, "SBool", otherwise)
     }
 
+  final protected def getSUnit(args: util.ArrayList[SValue], i: Int): Unit =
+    args.get(i) match {
+      case SUnit => ()
+      case otherwise => unexpectedType(i, "SUnit", otherwise)
+    }
+
   final protected def getSInt64(args: util.ArrayList[SValue], i: Int): Long =
     args.get(i) match {
       case SInt64(value) => value
@@ -894,25 +900,23 @@ private[lf] object SBuiltin {
 
   /** $checkPrecondition
     *    :: arg (template argument)
+    *    -> Unit
     *    -> Bool (false if ensure failed)
     *    -> Unit
     */
-  final case class SBCheckPrecond(templateId: TypeConName) extends SBuiltinPure(2) {
+  final case class SBCheckPrecond(templateId: TypeConName) extends SBuiltinPure(3) {
     override private[speedy] def executePure(args: util.ArrayList[SValue]): SUnit.type = {
-      if (
-        !(getSList(args, 1).iterator.forall(_ match {
-          case SBool(b) => b
-          case otherwise => crash(s"type mismatch SBCheckPrecond: expected SBool, got $otherwise")
-        }))
-      )
+      discard(getSUnit(args, 1))
+      val precond = getSBool(args, 2)
+      if (precond) SUnit
+      else
         throw SErrorDamlException(
           IE.TemplatePreconditionViolated(
             templateId = templateId,
             optLocation = None,
             arg = args.get(0).toUnnormalizedValue,
           )
         )
-      SUnit
     }
   }