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Closes #23681: Unnecessary reference duplicate in backend #23685

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Closes #23681: Unnecessary reference duplicate in backend #23685

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19 changes: 8 additions & 11 deletions compiler/src/dotty/tools/backend/jvm/BCodeBodyBuilder.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1713,26 +1713,23 @@ trait BCodeBodyBuilder extends BCodeSkelBuilder {
genCZJUMP(success, failure, Primitives.NE, BOOL, targetIfNoJump)
} else {
// l == r -> if (l eq null) r eq null else l.equals(r)
val eqEqTempLocal = locals.makeLocal(ObjectRef, nme.EQEQ_LOCAL_VAR.mangledString, defn.ObjectType, r.span)
val lNull = new asm.Label
val lNonNull = new asm.Label

genLoad(l, ObjectRef)
genLoad(r, ObjectRef) // load rhs --> (r)
stack.push(ObjectRef)
genLoad(r, ObjectRef)
genLoad(l, ObjectRef) // load lhs --> (l,r)
stack.pop()
locals.store(eqEqTempLocal)
bc dup ObjectRef
genCZJUMP(lNull, lNonNull, Primitives.EQ, ObjectRef, targetIfNoJump = lNull)
bc dup ObjectRef // duplicate top stack variable --> (l,l,r)
genCZJUMP(lNull, lNonNull, Primitives.EQ, ObjectRef, targetIfNoJump = lNull) // compare lhs with NULL --> (l,r)

markProgramPoint(lNull)
bc drop ObjectRef
locals.load(eqEqTempLocal)
genCZJUMP(success, failure, Primitives.EQ, ObjectRef, targetIfNoJump = lNonNull)
bc drop ObjectRef // drop top stack variable --> (r)
genCZJUMP(success, failure, Primitives.EQ, ObjectRef, targetIfNoJump = lNonNull) // --> (-)

markProgramPoint(lNonNull)
locals.load(eqEqTempLocal)
genCallMethod(defn.Any_equals, InvokeStyle.Virtual)
emit(asm.Opcodes.SWAP) //swap l and r for correct .equals ordering --> (r,l)
genCallMethod(defn.Any_equals, InvokeStyle.Virtual) // --> (-)
genCZJUMP(success, failure, Primitives.NE, BOOL, targetIfNoJump)
}
}
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24 changes: 11 additions & 13 deletions compiler/test/dotty/tools/backend/jvm/DottyBytecodeTests.scala
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Expand Up @@ -1168,7 +1168,7 @@ class DottyBytecodeTests extends DottyBytecodeTest {

val m1Meth = getMethod(fooClass, "m1")

assertSameCode(m1Meth, List(
assertSameCode(m1Meth,List(
VarOp(ALOAD, 1),
VarOp(ASTORE, 2),
VarOp(ALOAD, 2),
Expand All @@ -1189,29 +1189,27 @@ class DottyBytecodeTests extends DottyBytecodeTest {
VarOp(ILOAD, 5),
Op(IRETURN),
Label(19),
VarOp(ALOAD, 2),
Field(GETSTATIC, "scala/package$", "MODULE$", "Lscala/package$;"),
Invoke(INVOKEVIRTUAL, "scala/package$", "Nil", "()Lscala/collection/immutable/Nil$;", false),
VarOp(ALOAD, 2),
VarOp(ASTORE, 7),
Op(DUP),
Jump(IFNONNULL, Label(31)),
Jump(IFNONNULL, Label(29)),
Op(POP),
VarOp(ALOAD, 7),
Jump(IFNULL, Label(36)),
Jump(GOTO, Label(40)),
Label(31),
VarOp(ALOAD, 7),
Jump(IFNULL, Label(34)),
Jump(GOTO, Label(38)),
Label(29),
Op(SWAP),
Invoke(INVOKEVIRTUAL, "java/lang/Object", "equals", "(Ljava/lang/Object;)Z", false),
Jump(IFEQ, Label(40)),
Label(36),
Jump(IFEQ, Label(38)),
Label(34),
IntOp(BIPUSH, 20),
Op(IRETURN),
Label(40),
Label(38),
TypeOp(NEW, "scala/MatchError"),
Op(DUP),
VarOp(ALOAD, 2),
Invoke(INVOKESPECIAL, "scala/MatchError", "<init>", "(Ljava/lang/Object;)V", false),
Op(ATHROW),
Op(ATHROW)
))

// ---------------
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