[maglev] Fix overzealous DCHECK

Bug: v8:7700
Change-Id: Idf127095758289308010312deb9eb2b234cc453d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3652299Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80599}

src/maglev/maglev-regalloc.cc

@@ -668,8 +668,8 @@ void StraightForwardRegisterAllocator::AddMoveBeforeCurrentNode(
     ValueNode* node, compiler::InstructionOperand source,
     compiler::AllocatedOperand target) {
   Node* gap_move;
-  DCHECK_EQ(source.IsConstant(), IsConstantNode(node->opcode()));
   if (source.IsConstant()) {
+    DCHECK(IsConstantNode(node->opcode()));
     gap_move =
         Node::New<ConstantGapMove>(compilation_info_->zone(), {}, node, target);
   } else {