make opt_case_dispatch leaf

This instruction can be written without rb_funcall. It not only boosts
performance of case statements, but also makes room of future JIT
improvements.  Because opt_case_dispatch is about optimization this
should not be a bad thing to have.

----

trunk: ruby 2.6.0dev (2018-09-05 trunk 64634) [x86_64-darwin15]
ours: ruby 2.6.0dev (2018-09-12 leaf-insn 64688) [x86_64-darwin15]
last_commit=make opt_case_dispatch leaf
Calculating -------------------------------------
                          trunk        ours
        vm2_case_lit      1.366       2.012 i/s -       1.000 times in 0.731839s 0.497008s

Comparison:
                     vm2_case_lit
                ours:         2.0 i/s
               trunk:         1.4 i/s - 1.47x  slower



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64689 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

compile.c

@@ -1743,27 +1743,57 @@ iseq_set_local_table(rb_iseq_t *iseq, const ID *tbl)
 static int
 cdhash_cmp(VALUE val, VALUE lit)
 {
-    if (val == lit) return 0;
-    if (SPECIAL_CONST_P(lit)) {
-	return val != lit;
+    int tval, tlit;
+
+    if (val == lit) {
+        return 0;
     }
-    if (SPECIAL_CONST_P(val) || BUILTIN_TYPE(val) != BUILTIN_TYPE(lit)) {
-	return -1;
+    else if ((tlit = OBJ_BUILTIN_TYPE(lit)) == -1) {
+        return val != lit;
     }
-    if (BUILTIN_TYPE(lit) == T_STRING) {
-	return rb_str_hash_cmp(lit, val);
+    else if ((tval = OBJ_BUILTIN_TYPE(val)) == -1) {
+        return -1;
+    }
+    else if (tlit != tval) {
+        return -1;
+    }
+    else if (tlit == T_SYMBOL) {
+        return val != lit;
+    }
+    else if (tlit == T_STRING) {
+        return rb_str_hash_cmp(lit, val);
+    }
+    else if (tlit == T_BIGNUM) {
+        long x = FIX2LONG(rb_big_cmp(lit, val));
+
+        /* Given lit and val are both Bignum, x must be -1, 0, 1.
+         * There is no need to call rb_fix2int here. */
+        RUBY_ASSERT((x == 1) || (x == 0) || (x == -1));
+        return (int)x;
+    }
+    else if (tlit == T_FLOAT) {
+        return rb_float_cmp(lit, val);
+    }
+    else {
+        UNREACHABLE_RETURN(-1);
     }
-    return !rb_eql(lit, val);
 }
 
 static st_index_t
 cdhash_hash(VALUE a)
 {
-    if (SPECIAL_CONST_P(a)) return (st_index_t)a;
-    if (RB_TYPE_P(a, T_STRING)) return rb_str_hash(a);
-    {
-	VALUE hval = rb_hash(a);
-	return (st_index_t)FIX2LONG(hval);
+    switch (OBJ_BUILTIN_TYPE(a)) {
+      case -1:
+      case T_SYMBOL:
+        return (st_index_t)a;
+      case T_STRING:
+        return rb_str_hash(a);
+      case T_BIGNUM:
+        return FIX2LONG(rb_big_hash(a));
+      case T_FLOAT:
+        return rb_dbl_long_hash(RFLOAT_VALUE(a));
+      default:
+        UNREACHABLE_RETURN(0);
     }
 }
 

insns.def

@@ -1020,10 +1020,6 @@ opt_case_dispatch
 (CDHASH hash, OFFSET else_offset)
 (..., VALUE key)
 ()
-/* Case dispatch involves hash lookup, which inevitably compares
- * several objects each other.  The same discussion to
- * opt_newarray_max also goes here. */
-// attr bool leaf = false; /* has rb_any_cmp() */
 // attr rb_snum_t sp_inc = -1;
 {
     OFFSET dst = vm_case_dispatch(hash, else_offset, key);

vm_insnhelper.c

@@ -3355,7 +3355,7 @@ vm_case_dispatch(CDHASH hash, OFFSET else_offset, VALUE key)
 		}
 	    }
 	    if (st_lookup(RHASH_TBL_RAW(hash), key, &val)) {
-		return FIX2INT((VALUE)val);
+		return FIX2LONG((VALUE)val);
 	    }
 	    else {
 		return else_offset;