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Fix #4784: remove unsound constant folding #4788

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Merged
merged 1 commit into from
Jul 12, 2018
Merged

Fix #4784: remove unsound constant folding #4788

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18 changes: 2 additions & 16 deletions compiler/src/dotty/tools/dotc/transform/localopt/ConstantFold.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -75,7 +75,7 @@ import ast.Trees._
// isBool(ift.tpe) && !elsep.const.booleanValue =>
// cond.select(defn.Boolean_&&).appliedTo(elsep)
// the other case ins't handled intentionally. See previous case for explanation

case If(t @ Select(recv, _), thenp, elsep) if t.symbol eq defn.Boolean_! =>
If(recv, elsep, thenp)

Expand All @@ -98,11 +98,6 @@ import ast.Trees._
case (lhs, Literal(_)) if !lhs.isInstanceOf[Literal] && simplifyPhase.CommutativePrimitiveOperations.contains(sym) =>
rhs.select(sym).appliedTo(lhs)

case (l, _) if (sym == defn.Boolean_&&) && isConst(l.tpe) =>
val const = asConst(l.tpe).value.booleanValue
if (const) Block(lhs :: Nil, rhs)
else l

case (l, x: Literal) if sym == defn.Boolean_== && isBool(l.tpe) && isBool(x.tpe) =>
if (x.const.booleanValue) l
else l.select(defn.Boolean_!).ensureApplied
Expand All @@ -119,11 +114,6 @@ import ast.Trees._
if (!x.const.booleanValue) l
else l.select(defn.Boolean_!).ensureApplied

case (l: Literal, _) if (sym == defn.Boolean_||) && isConst(l.tpe) =>
val const = asConst(l.tpe).value.booleanValue
if (l.const.booleanValue) l
else Block(lhs :: Nil, rhs)

// case (Literal(Constant(1)), _) if sym == defn.Int_* => rhs
// case (Literal(Constant(0)), _) if sym == defn.Int_+ => rhs
// case (Literal(Constant(1L)), _) if sym == defn.Long_* => rhs
Expand All @@ -143,7 +133,7 @@ import ast.Trees._

case (l: Literal, r: Literal) =>
(l.tpe.widenTermRefExpr, r.tpe.widenTermRefExpr) match {
case (ConstantType(_), ConstantType(_)) =>
case (ConstantType(_), ConstantType(_)) =>
val s = ConstFold.apply(t)
if ((s ne null) && s.tpe.isInstanceOf[ConstantType]) Literal(s.tpe.asInstanceOf[ConstantType].value)
else t
Expand All @@ -169,8 +159,6 @@ import ast.Trees._
case t => t
}



def isSimilar(t1: Tree, t2: Tree)(implicit ctx: Context): Boolean = t1 match {
case t1: Apply =>
t2 match {
Expand Down Expand Up @@ -207,6 +195,4 @@ import ast.Trees._
}

def isBool(tpe: Type)(implicit ctx: Context): Boolean = tpe.derivesFrom(defn.BooleanClass)
def isConst(tpe: Type)(implicit ctx: Context): Boolean = tpe.isInstanceOf[ConstantType]
def asConst(tpe: Type)(implicit ctx: Context): ConstantType = tpe.asInstanceOf[ConstantType]
}
18 changes: 11 additions & 7 deletions compiler/test/dotty/tools/dotc/SimplifyTests.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -7,16 +7,16 @@ import dotty.tools.dotc.config.CompilerCommand
import dotty.tools.dotc.core.Contexts.FreshContext
import scala.tools.asm.tree.MethodNode

class SimplifyPosTests extends SimplifyTests(optimise = true)
class SimplifyNegTests extends SimplifyTests(optimise = false)
class SimplifyPosTests extends SimplifyTests(pos = true)
class SimplifyNegTests extends SimplifyTests(pos = false)

abstract class SimplifyTests(val optimise: Boolean) extends DottyBytecodeTest {
abstract class SimplifyTests(val pos: Boolean) extends DottyBytecodeTest {
override def initCtx = {
val ctx0 = super.initCtx
ctx0.setSetting(ctx0.settings.optimise, optimise)
ctx0.setSetting(ctx0.settings.optimise, pos)
}

def check(source: String, expected: String, shared: String = ""): Unit = {
def check(source: String, expected: String, shared: String = "", checkEqual: Boolean = pos): Unit = {
import ASMConverters._
val src =
s"""
Expand All @@ -41,7 +41,7 @@ abstract class SimplifyTests(val optimise: Boolean) extends DottyBytecodeTest {
val A = instructions("A")
val B = instructions("B")
val diff = diffInstructions(A, B)
if (optimise)
if (checkEqual)
assert(A == B, s"Bytecode doesn't match: (lhs = source, rhs = expected) \n$diff")
else
assert(A != B, s"Same Bytecodes without -optimise: you are testing the wrong thing!")
Expand Down Expand Up @@ -141,7 +141,7 @@ abstract class SimplifyTests(val optimise: Boolean) extends DottyBytecodeTest {
"""
|val i = 3
|val j = i + 4
|if(j - i >= (i + 1) / 2)
|if(j - i >= (i + 1) / 2)
| print(i + 1)
""",
"""
Expand Down Expand Up @@ -188,6 +188,10 @@ abstract class SimplifyTests(val optimise: Boolean) extends DottyBytecodeTest {
|}
""")

@Test def test4784 =
check(
"""{ println(1); false } || true""",
"""true""", checkEqual = false)

// @Test def listPatmapExample =
// check(
Expand Down