Allow dispatch to use a range of Class-ids in tests

runtime/vm/intermediate_language_x64.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/compiler.h"
@@ skipping 5789 matching lines @@
   Label is_ok;
   if (unary_checks().GetReceiverClassIdAt(0) == kSmiCid) {
     __ testq(value, Immediate(kSmiTagMask));
     __ j(ZERO, &is_ok);
   } else {
     __ testq(value, Immediate(kSmiTagMask));
     __ j(ZERO, deopt);
   }
   __ LoadClassId(temp, value);
 
-  if (IsDenseSwitch()) {
+  GrowableArray<CidRangeTarget> sorted_ic_data;
+  FlowGraphCompiler::SortICDataByCount(unary_checks(), &sorted_ic_data,
+                                       /* drop_smi = */ true);
+
+  if (sorted_ic_data.length() > 4 && IsDenseSwitch()) {
     ASSERT(cids_[0] < cids_[cids_.length() - 1]);
     __ subq(temp, Immediate(cids_[0]));
     __ cmpq(temp, Immediate(cids_[cids_.length() - 1] - cids_[0]));
     __ j(ABOVE, deopt);
 
     intptr_t mask = ComputeCidMask();
     if (!IsDenseMask(mask)) {
       // Only need mask if there are missing numbers in the range.
       ASSERT(cids_.length() > 2);
       Register mask_reg = locs()->temp(1).reg();
       __ movq(mask_reg, Immediate(mask));
       __ btq(mask_reg, temp);
       __ j(NOT_CARRY, deopt);
     }
   } else {
-    GrowableArray<CidTarget> sorted_ic_data;
-    FlowGraphCompiler::SortICDataByCount(unary_checks(), &sorted_ic_data,
-                                         /* drop_smi = */ true);
     const intptr_t num_checks = sorted_ic_data.length();
     const bool use_near_jump = num_checks < 5;
+    int bias = 0;
     for (intptr_t i = 0; i < num_checks; i++) {
-      const intptr_t cid = sorted_ic_data[i].cid;
-      __ cmpl(temp, Immediate(cid));
-      if (i == (num_checks - 1)) {
-        __ j(NOT_EQUAL, deopt);
+      const intptr_t cid_start = sorted_ic_data[i].cid_start;
+      const intptr_t cid_end = sorted_ic_data[i].cid_end;
+      ASSERT(cid_start > kSmiCid || cid_end < kSmiCid);
+      Condition no_match, match;
+      if (cid_start == cid_end) {
+        __ cmpl(temp, Immediate(cid_start - bias));
+        no_match = NOT_EQUAL;
+        match = EQUAL;
+      } else {
+        // For class ID ranges use a subtract followed by an unsigned
+        // comparison to check both ends of the ranges with one comparison.
+        __ addl(temp, Immediate(bias - cid_start));
+        bias = cid_start;
+        __ cmpl(temp, Immediate(cid_end - cid_start));
+        no_match = ABOVE;
+        match = BELOW_EQUAL;
+      }
+
+      if (i == num_checks - 1) {
+        __ j(no_match, deopt);
       } else {
         if (use_near_jump) {
-          __ j(EQUAL, &is_ok, Assembler::kNearJump);
+          __ j(match, &is_ok, Assembler::kNearJump);
         } else {
-          __ j(EQUAL, &is_ok);
+          __ j(match, &is_ok);
         }
       }
     }
   }
   __ Bind(&is_ok);
 }
 
 
 LocationSummary* CheckSmiInstr::MakeLocationSummary(Zone* zone,
                                                     bool opt) const {
@@ skipping 899 matching lines @@
   __ Drop(1);
   __ popq(result);
 }
 
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64