Temp commit: Potential scan -> Nonrelocatable scan.

Author: rudi-c

src/asm_writing/icinfo.cpp

@@ -340,7 +340,7 @@ bool ICInfo::isMegamorphic() {
 void ICInfo::visitGCReferences(gc::GCVisitor* v) {
     for (const auto& p : ics_list) {
         for (auto& slot : p->slots) {
-            v->visitPotentialRange(&slot.gc_references[0], &slot.gc_references[slot.gc_references.size()]);
+            v->visitNonRelocatableRange(&slot.gc_references[0], &slot.gc_references[slot.gc_references.size()]);
         }
     }
 }

src/codegen/irgen/hooks.cpp

@@ -784,7 +784,7 @@ CompiledFunction::~CompiledFunction() {
 void CompiledFunction::visitAllCompiledFunctions(GCVisitor* visitor) {
     for (CompiledFunction* cf : all_compiled_functions) {
         for (const void* ptr : cf->pointers_in_code) {
-            visitor->visitPotentialRedundant(const_cast<void*>(ptr));
+            visitor->visitNonRelocatable(const_cast<void*>(ptr));
         }
     }
 }

src/gc/gc.h

@@ -77,6 +77,14 @@ class GCVisitor {
     virtual void visitRedundantRange(void** start, void** end) {}
     virtual void visitPotentialRedundant(void* p) {}
     virtual void visitPotentialRangeRedundant(void* const* start, void* const* end) {}
+
+    // Visit pointers to objects that we know cannot be moved.
+    // This is often used to scan a pointer that's a copy of a pointer stored in a place that
+    // we cannot easily scanned (like generated code).
+    // This default to visitPotential for now (which also cannot be moved) but we may want to
+    // change that later for performance.
+    void visitNonRelocatable(void* p) { visitPotential(p); }
+    void visitNonRelocatableRange(void** start, void** end) { visitPotentialRange(start, end); }
 };
 
 enum class GCKind : uint8_t {