https://git.ruby-lang.org/ruby.git/commit/?id=2e8d8d10f2

From 2e8d8d10f211b52f520109a8bfdd3bb3a6eab8c0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=8D=9C=E9=83=A8=E6=98=8C=E5=B9=B3?=
 <shyouhei@r...>
Date: Wed, 10 Jun 2020 13:42:30 +0900
Subject: rb_ary_behead: do not goto into a branch

I'm not necessarily against every goto in general, but jumping into a
branch is definitely a bad idea.  Better refactor.

diff --git a/array.c b/array.c
index bbfbc2b..d6a2a7a 100644
--- a/array.c
+++ b/array.c
@@ -1524,36 +1524,50 @@ rb_ary_shift_m(int argc, VALUE *argv, VALUE ary) https://github.com/ruby/ruby/blob/trunk/array.c#L1524
     return result;
 }
 
-MJIT_FUNC_EXPORTED VALUE
-rb_ary_behead(VALUE ary, long n)
+static VALUE
+behead_shared(VALUE ary, long n)
 {
-    if (n<=0) return ary;
-
+    assert(ARY_SHARED_P(ary));
     rb_ary_modify_check(ary);
-    if (ARY_SHARED_P(ary)) {
-        if (ARY_SHARED_ROOT_OCCUPIED(ARY_SHARED_ROOT(ary))) {
-	  setup_occupied_shared:
-	    ary_mem_clear(ary, 0, n);
-	}
-        ARY_INCREASE_PTR(ary, n);
-    }
-    else {
-	if (RARRAY_LEN(ary) < ARY_DEFAULT_SIZE) {
-            RARRAY_PTR_USE_TRANSIENT(ary, ptr, {
-                MEMMOVE(ptr, ptr+n, VALUE, RARRAY_LEN(ary)-n);
-	    }); /* WB: no new reference */
-	}
-	else {
-	    ary_make_shared(ary);
-	    goto setup_occupied_shared;
-	}
+    if (ARY_SHARED_ROOT_OCCUPIED(ARY_SHARED_ROOT(ary))) {
+        ary_mem_clear(ary, 0, n);
     }
+    ARY_INCREASE_PTR(ary, n);
     ARY_INCREASE_LEN(ary, -n);
+    ary_verify(ary);
+    return ary;
+}
 
+static VALUE
+behead_transient(VALUE ary, long n)
+{
+    rb_ary_modify_check(ary);
+    RARRAY_PTR_USE_TRANSIENT(ary, ptr, {
+        MEMMOVE(ptr, ptr+n, VALUE, RARRAY_LEN(ary)-n);
+    }); /* WB: no new reference */
+    ARY_INCREASE_LEN(ary, -n);
     ary_verify(ary);
     return ary;
 }
 
+MJIT_FUNC_EXPORTED VALUE
+rb_ary_behead(VALUE ary, long n)
+{
+    if (n <= 0) {
+        return ary;
+    }
+    else if (ARY_SHARED_P(ary)) {
+        return behead_shared(ary, n);
+    }
+    else if (RARRAY_LEN(ary) >= ARY_DEFAULT_SIZE) {
+        ary_make_shared(ary);
+        return behead_shared(ary, n);
+    }
+    else {
+        return behead_transient(ary, n);
+    }
+}
+
 static VALUE
 ary_ensure_room_for_unshift(VALUE ary, int argc)
 {
-- 
cgit v0.10.2


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