Alternative scheme for resHi as an Int32Array of size 1.

sjrd · sjrd · commit 3f29eb1b1d6f · 2025-07-25T10:29:34.000+02:00
Sadly, that doesn't fix the GCC issue.

It may have performance, especially in multi-module outputs, as we
don't need to mutate a foreign var.
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/CoreJSLib.scala
@@ -520,7 +520,13 @@ private[emitter] object CoreJSLib {
 
     private def defineResHi(): List[Tree] = {
       condDefs(!allowBigIntsForLongs)(
-        extractWithGlobals(globallyMutableVarDef(VarField.resHi, VarField.setResHi, CoreVar, int(0)))
+        extractWithGlobals(globallyMutableVarDef(VarField.resHi, VarField.setResHi, CoreVar, {
+          if (esVersion >= ESVersion.ES2015) {
+            New(globalRef("Int32Array"), List(int(1)))
+          } else {
+            ArrayConstr(List(int(0)))
+          }
+        }))
       )
     }
 
@@ -1504,12 +1510,12 @@ private[emitter] object CoreJSLib {
             } else {
               If(v === Null(), {
                 Block(
-                  globalVar(VarField.resHi, CoreVar) := 0,
+                  genResHi() := 0,
                   0
                 )
               }, {
                 Block(
-                  globalVar(VarField.resHi, CoreVar) := v DOT cpn.hi,
+                  genResHi() := v DOT cpn.hi,
                   v DOT cpn.lo
                 )
               })
@@ -1536,12 +1542,12 @@ private[emitter] object CoreJSLib {
             } else {
               If(v === Null(), {
                 Block(
-                  globalVar(VarField.resHi, CoreVar) := 0,
+                  genResHi() := 0,
                   Return(0)
                 )
               }, {
                 Block(
-                  globalVar(VarField.resHi, CoreVar) := v DOT cpn.hi,
+                  genResHi() := v DOT cpn.hi,
                   Return(v DOT cpn.lo)
                 )
               })
@@ -1596,7 +1602,7 @@ private[emitter] object CoreJSLib {
                   Block(
                       boundsCheck,
                       i := (i << 1),
-                      globalVar(VarField.resHi, CoreVar) := BracketSelect(This().u, (i + 1) | 0),
+                      genResHi() := BracketSelect(This().u, (i + 1) | 0),
                       Return(BracketSelect(This().u, i))
                   )
                 }),
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/FunctionEmitter.scala
@@ -1742,22 +1742,16 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
                   js.Block(transformStat(rhs, tailPosLabels = Set.empty), js.Return(js.Undefined()))
                 case LongType if !useBigIntForLongs =>
                   val (lo, hi) = transformLongExpr(rhs)
-                  val resHi = globalVar(VarField.resHi, CoreVar)
-                  if (hi == resHi) {
+                  if (isResHi(hi)) {
                     /* No need to assign resHi to itself.
                      * This happens for all tail calls of Long-returning functions.
                      */
                     js.Return(lo)
                   } else {
                     val tempLo = newSyntheticVar()
-                    val resHiAssign = if (needToUseGloballyMutableVarSetter(CoreVar)) {
-                      js.Apply(globalVar(VarField.setResHi, CoreVar), hi :: Nil)
-                    } else {
-                      js.Assign(resHi, hi)
-                    }
                     js.Block(
                       genConst(tempLo, lo),
-                      resHiAssign,
+                      js.Assign(genResHi(), hi),
                       js.Return(js.VarRef(tempLo))
                     )
                   }
@@ -3230,7 +3224,7 @@ private[emitter] class FunctionEmitter(sjsGen: SJSGen) {
       }
 
       def withResHi(jsTree: js.Tree): (js.Tree, js.Tree) =
-        (jsTree, globalVar(VarField.resHi, CoreVar))
+        (jsTree, genResHi())
 
       tree match {
         // Control flow constructs
diff --git a/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala b/linker/shared/src/main/scala/org/scalajs/linker/backend/emitter/SJSGen.scala
@@ -186,6 +186,21 @@ private[emitter] final class SJSGen(
     else Nil
   }
 
+  def genResHi()(
+      implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
+      pos: Position): Tree = {
+    BracketSelect(globalVar(VarField.resHi, CoreVar), IntLiteral(0))
+  }
+
+  def isResHi(tree: Tree)(
+      implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
+      pos: Position): Boolean = {
+    tree match {
+      case BracketSelect(qual, IntLiteral(0)) => qual == globalVar(VarField.resHi, CoreVar)
+      case _                                  => false
+    }
+  }
+
   def genZeroOf(tpe: Type)(
       implicit moduleContext: ModuleContext, globalKnowledge: GlobalKnowledge,
       pos: Position): Tree = {
diff --git a/project/Build.scala b/project/Build.scala
@@ -2080,7 +2080,7 @@ object Build {
             } else {
               Some(ExpectedSizes(
                   fastLink = 424000 to 425000,
-                  fullLink = 282000 to 283000,
+                  fullLink = 283000 to 284000,
                   fastLinkGz = 61000 to 62000,
                   fullLinkGz = 44000 to 45000,
               ))
@@ -2097,7 +2097,7 @@ object Build {
             } else {
               Some(ExpectedSizes(
                   fastLink = 300000 to 301000,
-                  fullLink = 259000 to 260000,
+                  fullLink = 260000 to 261000,
                   fastLinkGz = 47000 to 48000,
                   fullLinkGz = 43000 to 44000,
               ))
