YJIT: Leave cfp->pc uninitialized for VM_FRAME_MAGIC_CFUNC

C function frames don't need to use the VM-specific pc field to run
properly. When pushing a control frame from output code, save one
instruction by leaving the field uninitialized.

Fix-up rb_vm_svar_lep(), which is used while setting local variables via
Regexp#=~. Use cfp->iseq as a secondary signal so it can stop assuming
that all CFUNC frames always have zero pc's.

1 files changed, 1 insertions, 1 deletions

diff --git a/vm.c b/vm.c
index 31725ae2d0..69d57913a4 100644
--- a/vm.c
+++ b/vm.c
@@ -1609,7 +1609,7 @@ rb_vm_invoke_proc_with_self(rb_execution_context_t *ec, rb_proc_t *proc, VALUE s
 VALUE *
 rb_vm_svar_lep(const rb_execution_context_t *ec, const rb_control_frame_t *cfp)
 {
-    while (cfp->pc == 0) {
+    while (cfp->pc == 0 || cfp->iseq == 0) {
         if (VM_FRAME_TYPE(cfp) ==  VM_FRAME_MAGIC_IFUNC) {
             struct vm_ifunc *ifunc = (struct vm_ifunc *)cfp->iseq;
             return ifunc->svar_lep;