Opt: Rewrite 1 + ~x to -x.

sjrd · sjrd · commit 52668c3be62d · 2025-05-22T16:34:31.000+02:00
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala b/linker/shared/src/main/scala/org/scalajs/linker/frontend/optimizer/OptimizerCore.scala
@@ -4141,6 +4141,10 @@ private[optimizer] abstract class OptimizerCore(
                   PreTransLit(IntLiteral(y)), z)) =>
             foldBinaryOp(innerOp, PreTransLit(IntLiteral(x + y)), z)
 
+          // 1 + (-1 ^ x) == 1 + ~x == -x == 0 - x (this appears when optimizing a Range with step == -1)
+          case (PreTransLit(IntLiteral(1)), PreTransBinaryOp(Int_^, PreTransLit(IntLiteral(-1)), x)) =>
+            foldBinaryOp(Int_-, PreTransLit(IntLiteral(0)), x)
+
           case _ => default
         }
 

Original file line number	Diff line number	Diff line change
`@@ -4141,6 +4141,10 @@ private[optimizer] abstract class OptimizerCore(`
`4141`	`4141`	`PreTransLit(IntLiteral(y)), z)) =>`
`4142`	`4142`	`foldBinaryOp(innerOp, PreTransLit(IntLiteral(x + y)), z)`
`4143`	`4143`
	`4144`	`+ // 1 + (-1 ^ x) == 1 + ~x == -x == 0 - x (this appears when optimizing a Range with step == -1)`
	`4145`	`+ case (PreTransLit(IntLiteral(1)), PreTransBinaryOp(Int_^, PreTransLit(IntLiteral(-1)), x)) =>`
	`4146`	`+ foldBinaryOp(Int_-, PreTransLit(IntLiteral(0)), x)`
	`4147`	`+`
`4144`	`4148`	`case _ => default`
`4145`	`4149`	`}`
`4146`	`4150`