merge revision(s) 1f115f141dd17f75049a5e17107906c5bcc372e1: [Backport #19246]

	Speed up rebuilding the loaded feature index

	Rebuilding the loaded feature index slowed down with the bug fix
	for #17885 in 79a4484a072e9769b603e7b4fbdb15b1d7eccb15.  The
	slowdown was extreme if realpath emulation was used, but even when
	not emulated, it could be about 10x slower.

	This adds loaded_features_realpath_map to rb_vm_struct. This is a
	hidden hash mapping loaded feature paths to realpaths. When
	rebuilding the loaded feature index, look at this hash to get
	cached realpath values, and skip calling rb_check_realpath if a
	cached value is found.

	Fixes [Bug #19246]
	---
	 load.c    | 27 +++++++++++++++++++++++----
	 vm.c      |  2 ++
	 vm_core.h |  1 +
	 3 files changed, 26 insertions(+), 4 deletions(-)

1 files changed, 2 insertions, 0 deletions

diff --git a/vm.c b/vm.c
index 0126f0c6de..12634d687e 100644
--- a/vm.c
+++ b/vm.c
@@ -2539,6 +2539,7 @@ rb_vm_update_references(void *ptr)
         vm->loaded_features = rb_gc_location(vm->loaded_features);
         vm->loaded_features_snapshot = rb_gc_location(vm->loaded_features_snapshot);
         vm->loaded_features_realpaths = rb_gc_location(vm->loaded_features_realpaths);
+        vm->loaded_features_realpath_map = rb_gc_location(vm->loaded_features_realpath_map);
         vm->top_self = rb_gc_location(vm->top_self);
         vm->orig_progname = rb_gc_location(vm->orig_progname);
 
@@ -2630,6 +2631,7 @@ rb_vm_mark(void *ptr)
         rb_gc_mark_movable(vm->loaded_features);
         rb_gc_mark_movable(vm->loaded_features_snapshot);
         rb_gc_mark_movable(vm->loaded_features_realpaths);
+        rb_gc_mark_movable(vm->loaded_features_realpath_map);
         rb_gc_mark_movable(vm->top_self);
         rb_gc_mark_movable(vm->orig_progname);
         RUBY_MARK_MOVABLE_UNLESS_NULL(vm->coverages);