Drop obsoleted BUILTIN_ATTR_NO_GC attribute

The thing that has used this in the past was very buggy, and we've never
revisied it. Let's remove it until we need it again.

compile.c

@@ -8636,9 +8636,6 @@ compile_builtin_attr(rb_iseq_t *iseq, const NODE *node)
         if (strcmp(RSTRING_PTR(string), "leaf") == 0) {
             ISEQ_BODY(iseq)->builtin_attrs |= BUILTIN_ATTR_LEAF;
         }
-        else if (strcmp(RSTRING_PTR(string), "no_gc") == 0) {
-            ISEQ_BODY(iseq)->builtin_attrs |= BUILTIN_ATTR_NO_GC;
-        }
         else {
             goto unknown_arg;
         }

lib/ruby_vm/rjit/insn_compiler.rb

@@ -4924,13 +4924,10 @@ module RubyVM::RJIT
 
       asm.comment('inlined leaf builtin')
 
-      # Skip this if it doesn't trigger GC
-      if iseq.body.builtin_attrs & C::BUILTIN_ATTR_NO_GC == 0
-        # The callee may allocate, e.g. Integer#abs on a Bignum.
-        # Save SP for GC, save PC for allocation tracing, and prepare
-        # for global invalidation after GC's VM lock contention.
-        jit_prepare_routine_call(jit, ctx, asm)
-      end
+      # The callee may allocate, e.g. Integer#abs on a Bignum.
+      # Save SP for GC, save PC for allocation tracing, and prepare
+      # for global invalidation after GC's VM lock contention.
+      jit_prepare_routine_call(jit, ctx, asm)
 
       # Call the builtin func (ec, recv, arg1, arg2, ...)
       asm.mov(C_ARGS[0], EC)

rjit_c.rb

@@ -364,7 +364,6 @@ module RubyVM::RJIT # :nodoc: all
   C::BOP_OR = Primitive.cexpr! %q{ SIZET2NUM(BOP_OR) }
   C::BOP_PLUS = Primitive.cexpr! %q{ SIZET2NUM(BOP_PLUS) }
   C::BUILTIN_ATTR_LEAF = Primitive.cexpr! %q{ SIZET2NUM(BUILTIN_ATTR_LEAF) }
-  C::BUILTIN_ATTR_NO_GC = Primitive.cexpr! %q{ SIZET2NUM(BUILTIN_ATTR_NO_GC) }
   C::HASH_REDEFINED_OP_FLAG = Primitive.cexpr! %q{ SIZET2NUM(HASH_REDEFINED_OP_FLAG) }
   C::INTEGER_REDEFINED_OP_FLAG = Primitive.cexpr! %q{ SIZET2NUM(INTEGER_REDEFINED_OP_FLAG) }
   C::INVALID_SHAPE_ID = Primitive.cexpr! %q{ SIZET2NUM(INVALID_SHAPE_ID) }

tool/mk_builtin_loader.rb

@@ -6,7 +6,7 @@ require_relative 'ruby_vm/helpers/c_escape'
 
 SUBLIBS = {}
 REQUIRED = {}
-BUILTIN_ATTRS = %w[leaf no_gc]
+BUILTIN_ATTRS = %w[leaf]
 
 def string_literal(lit, str = [])
   while lit

tool/rjit/bindgen.rb

@@ -396,7 +396,6 @@ generator = BindingGenerator.new(
       BOP_OR
       BOP_PLUS
       BUILTIN_ATTR_LEAF
-      BUILTIN_ATTR_NO_GC
       HASH_REDEFINED_OP_FLAG
       INTEGER_REDEFINED_OP_FLAG
       INVALID_SHAPE_ID

vm_core.h

@@ -365,10 +365,8 @@ enum rb_iseq_type {
 enum rb_builtin_attr {
     // The iseq does not call methods.
     BUILTIN_ATTR_LEAF = 0x01,
-    // The iseq does not allocate objects.
-    BUILTIN_ATTR_NO_GC = 0x02,
     // This iseq only contains single `opt_invokebuiltin_delegate_leave` instruction with 0 arguments.
-    BUILTIN_ATTR_SINGLE_NOARG_INLINE = 0x04,
+    BUILTIN_ATTR_SINGLE_NOARG_INLINE = 0x02,
 };
 
 typedef VALUE (*rb_jit_func_t)(struct rb_execution_context_struct *, struct rb_control_frame_struct *);

yjit/src/codegen.rs

@@ -6294,13 +6294,10 @@ fn gen_send_iseq(
             asm_comment!(asm, "inlined leaf builtin");
             gen_counter_incr(asm, Counter::num_send_leaf_builtin);
 
-            // Skip this if it doesn't trigger GC
-            if builtin_attrs & BUILTIN_ATTR_NO_GC == 0 {
-                // The callee may allocate, e.g. Integer#abs on a Bignum.
-                // Save SP for GC, save PC for allocation tracing, and prepare
-                // for global invalidation after GC's VM lock contention.
-                jit_prepare_routine_call(jit, asm);
-            }
+            // The callee may allocate, e.g. Integer#abs on a Bignum.
+            // Save SP for GC, save PC for allocation tracing, and prepare
+            // for global invalidation after GC's VM lock contention.
+            jit_prepare_routine_call(jit, asm);
 
             // Call the builtin func (ec, recv, arg1, arg2, ...)
             let mut args = vec![EC];

yjit/src/cruby_bindings.inc.rs

@@ -448,8 +448,7 @@ pub struct iseq_inline_cvar_cache_entry {
     pub entry: *mut rb_cvar_class_tbl_entry,
 }
 pub const BUILTIN_ATTR_LEAF: rb_builtin_attr = 1;
-pub const BUILTIN_ATTR_NO_GC: rb_builtin_attr = 2;
-pub const BUILTIN_ATTR_SINGLE_NOARG_INLINE: rb_builtin_attr = 4;
+pub const BUILTIN_ATTR_SINGLE_NOARG_INLINE: rb_builtin_attr = 2;
 pub type rb_builtin_attr = u32;
 #[repr(C)]
 #[derive(Debug, Copy, Clone)]