diff options
| -rw-r--r-- | src/compiler/scala/tools/nsc/backend/icode/GenICode.scala | 9 | ||||
| -rw-r--r-- | test/files/run/t7852.check | 22 |
2 files changed, 12 insertions, 19 deletions
diff --git a/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala b/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala index 1413add240..a80fee876e 100644 --- a/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala +++ b/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala @@ -1320,6 +1320,7 @@ abstract class GenICode extends SubComponent { */ def isNull(t: Tree) = cond(t) { case Literal(Constant(null)) => true } def isLiteral(t: Tree) = cond(t) { case Literal(_) => true } + def isNonNullExpr(t: Tree) = isLiteral(t) || ((t.symbol ne null) && t.symbol.isModule) /* If l or r is constant null, returns the other ; otherwise null */ def ifOneIsNull(l: Tree, r: Tree) = if (isNull(l)) r else if (isNull(r)) l else null @@ -1515,8 +1516,12 @@ abstract class GenICode extends SubComponent { val branchesReachable = !ctx1.bb.ignore ctx1.bb emitOnly CZJUMP(thenCtx.bb, elseCtx.bb, EQ, ObjectReference) branchesReachable - } else if (isLiteral(l)) { - // "" == expr -> "".equals(expr) (no null check) + } else if (isNonNullExpr(l)) { + // Avoid null check if L is statically non-null. + // + // "" == expr -> "".equals(expr) + // Nil == expr -> Nil.equals(expr) + // // Common enough (through pattern matching) to treat this specially here rather than // hoping that -Yconst-opt is enabled. The impossible branches for null checks lead // to spurious "branch not covered" warnings in Jacoco code coverage. diff --git a/test/files/run/t7852.check b/test/files/run/t7852.check index 648f464aa2..ec63f5378c 100644 --- a/test/files/run/t7852.check +++ b/test/files/run/t7852.check @@ -21,30 +21,18 @@ module GETSTATIC scala/collection/immutable/Nil$.MODULE$ : Lscala/collection/immutable/Nil$; ALOAD 0 INVOKEVIRTUAL java/lang/Object.toString ()Ljava/lang/String; - ASTORE 1 - DUP - IFNONNULL L0 - POP - ALOAD 1 - IFNULL L1 - GOTO L2 - L0 - FRAME FULL [Lean java/lang/String] [scala/collection/immutable/Nil$] - ALOAD 1 INVOKEVIRTUAL java/lang/Object.equals (Ljava/lang/Object;)Z - IFEQ L2 - L1 - FRAME SAME + IFEQ L0 ICONST_1 - GOTO L3 - L2 + GOTO L1 + L0 FRAME SAME ICONST_0 - L3 + L1 FRAME SAME1 I POP RETURN MAXSTACK = 2 - MAXLOCALS = 2 + MAXLOCALS = 1 |