Revert "Optimizations to IC stub for unoptimized code performance on x64."

runtime/vm/stub_code_ia32.cc

Index: runtime/vm/stub_code_ia32.cc
diff --git a/runtime/vm/stub_code_ia32.cc b/runtime/vm/stub_code_ia32.cc
index bcda1ff51f63f5ec70993f48e73fd8e59e983981..ce6521d339ddb381173946cb60d402c2210b8d9d 100644
--- a/runtime/vm/stub_code_ia32.cc
+++ b/runtime/vm/stub_code_ia32.cc
@@ -1259,9 +1259,13 @@ static void EmitFastSmiOp(Assembler* assembler,
   __ Bind(&ok);
 #endif
   if (FLAG_optimization_counter_threshold >= 0) {
+    // Update counter.
     const intptr_t count_offset = ICData::CountIndexFor(num_args) * kWordSize;
-    // Update counter, ignore overflow.
-    __ addl(Address(EBX, count_offset), Immediate(Smi::RawValue(1)));
+    __ movl(ECX, Address(EBX, count_offset));
+    __ addl(ECX, Immediate(Smi::RawValue(1)));
+    __ movl(EDI, Immediate(Smi::RawValue(Smi::kMaxValue)));
+    __ cmovno(EDI, ECX);
+    __ StoreIntoSmiField(Address(EBX, count_offset), EDI);
   }
   __ ret();
 }
@@ -1283,7 +1287,7 @@ void StubCode::GenerateNArgsCheckInlineCacheStub(
     const RuntimeEntry& handle_ic_miss,
     Token::Kind kind,
     bool optimized) {
-  ASSERT(num_args == 1 || num_args == 2);
+  ASSERT(num_args > 0);
 #if defined(DEBUG)
   {
     Label ok;
@@ -1318,74 +1322,60 @@ void StubCode::GenerateNArgsCheckInlineCacheStub(
   // Load arguments descriptor into EDX.
   __ movl(EDX, FieldAddress(ECX, ICData::arguments_descriptor_offset()));
   // Loop that checks if there is an IC data match.
-  Label loop, found, miss;
   // ECX: IC data object (preserved).
   __ movl(EBX, FieldAddress(ECX, ICData::ic_data_offset()));
   // EBX: ic_data_array with check entries: classes and target functions.
   __ leal(EBX, FieldAddress(EBX, Array::data_offset()));
   // EBX: points directly to the first ic data array element.
 
-  // Get argument descriptor into EAX.  In the 1-argument case this is the
-  // last time we need the argument descriptor, and we reuse EAX for the
-  // class IDs from the IC descriptor.  In the 2-argument case we preserve
-  // the argument descriptor in EAX.
+  // Get the receiver's class ID (first read number of arguments from
+  // arguments descriptor array and then access the receiver from the stack).
   __ movl(EAX, FieldAddress(EDX, ArgumentsDescriptor::count_offset()));
-  if (num_args == 1) {
-    // Load first argument into EDI.
-    __ movl(EDI,
-            Address(ESP, EAX, TIMES_2, 0));  // EAX (argument count) is Smi.
-    __ LoadTaggedClassIdMayBeSmi(EAX, EDI);
-    // EAX: first argument class ID as Smi.
-    __ movl(EDI, Address(EBX, 0));
-  }
-
-  __ Comment("ICData loop");
+  __ movl(EDI, Address(ESP, EAX, TIMES_2, 0));  // EAX (argument_count) is smi.
+  __ LoadTaggedClassIdMayBeSmi(EAX, EDI);
 
-  // We unroll the generic one that is generated once more than the others.
-  bool optimize = kind == Token::kILLEGAL;
-  const intptr_t target_offset = ICData::TargetIndexFor(num_args) * kWordSize;
-  const intptr_t count_offset = ICData::CountIndexFor(num_args) * kWordSize;
+  // EAX: receiver's class ID (smi).
+  __ movl(EDI, Address(EBX, 0));  // First class id (smi) to check.
+  Label loop, update, test, found;
+  __ jmp(&test);
 
+  __ Comment("ICData loop");
   __ Bind(&loop);
-  for (int unroll = optimize ? 4 : 2; unroll >= 0; unroll--) {
-    Label update;
-    for (int i = 0; i < num_args; i++) {
-      if (num_args == 2) {
-        // Load ith argument into EDI.
-        __ movl(EDI, Address(ESP, EAX, TIMES_2, -kWordSize * i));
-        __ LoadTaggedClassIdMayBeSmi(EDI, EDI);
-        // EDI: ith argument class ID (smi).
-        __ cmpl(EDI, Address(EBX, kWordSize * i));  // Class id match?
-      } else {
-        __ cmpl(EDI, EAX);  // Class id match?
-      }
-      if (i < (num_args - 1)) {
-        __ j(NOT_EQUAL, &update);  // Continue.
-      } else {
-        // Last check, all checks before matched.
-        __ j(EQUAL, &found);  // Break.
-      }
+  for (int i = 0; i < num_args; i++) {
+    if (i > 0) {
+      // If not the first, load the next argument's class ID.
+      __ movl(EAX, FieldAddress(EDX, ArgumentsDescriptor::count_offset()));
+      __ movl(EDI, Address(ESP, EAX, TIMES_2, -i * kWordSize));
+      __ LoadTaggedClassIdMayBeSmi(EAX, EDI);
+
+      // EAX: next argument class ID (smi).
+      __ movl(EDI, Address(EBX, i * kWordSize));
+      // EDI: next class ID to check (smi).
     }
-    __ Bind(&update);
-
-    const intptr_t entry_size =
-        ICData::TestEntryLengthFor(num_args) * kWordSize;
-    __ addl(EBX, Immediate(entry_size));  // Next entry.
-    if (num_args == 2) {
-      __ cmpl(Address(EBX, -entry_size),
-              Immediate(Smi::RawValue(kIllegalCid)));  // Done?
+    __ cmpl(EAX, EDI);  // Class id match?
+    if (i < (num_args - 1)) {
+      __ j(NOT_EQUAL, &update);  // Continue.
     } else {
-      __ cmpl(EDI, Immediate(Smi::RawValue(kIllegalCid)));  // Done?
-      __ movl(EDI, Address(EBX, 0));
-    }
-    if (unroll == 0) {
-      __ j(NOT_EQUAL, &loop);
-    } else {
-      __ j(EQUAL, &miss);
+      // Last check, all checks before matched.
+      __ j(EQUAL, &found);  // Break.
     }
   }
+  __ Bind(&update);
+  // Reload receiver class ID.  It has not been destroyed when num_args == 1.
+  if (num_args > 1) {
+    __ movl(EAX, FieldAddress(EDX, ArgumentsDescriptor::count_offset()));
+    __ movl(EDI, Address(ESP, EAX, TIMES_2, 0));
+    __ LoadTaggedClassIdMayBeSmi(EAX, EDI);
+  }
+
+  const intptr_t entry_size = ICData::TestEntryLengthFor(num_args) * kWordSize;
+  __ addl(EBX, Immediate(entry_size));  // Next entry.
+  __ movl(EDI, Address(EBX, 0));        // Next class ID.
+
+  __ Bind(&test);
+  __ cmpl(EDI, Immediate(Smi::RawValue(kIllegalCid)));  // Done?
+  __ j(NOT_EQUAL, &loop, Assembler::kNearJump);
 
-  __ Bind(&miss);
   __ Comment("IC miss");
   // Compute address of arguments (first read number of arguments from
   // arguments descriptor array and then compute address on the stack).
@@ -1422,10 +1412,15 @@ void StubCode::GenerateNArgsCheckInlineCacheStub(
   __ Bind(&found);
 
   // EBX: Pointer to an IC data check group.
+  const intptr_t target_offset = ICData::TargetIndexFor(num_args) * kWordSize;
+  const intptr_t count_offset = ICData::CountIndexFor(num_args) * kWordSize;
   if (FLAG_optimization_counter_threshold >= 0) {
     __ Comment("Update caller's counter");
-    // Ignore overflow.
-    __ addl(Address(EBX, count_offset), Immediate(Smi::RawValue(1)));
+    __ movl(EAX, Address(EBX, count_offset));
+    __ addl(EAX, Immediate(Smi::RawValue(1)));
+    __ movl(EDI, Immediate(Smi::RawValue(Smi::kMaxValue)));
+    __ cmovno(EDI, EAX);
+    __ StoreIntoSmiField(Address(EBX, count_offset), EDI);
   }
 
   __ movl(EAX, Address(EBX, target_offset));
@@ -1560,8 +1555,12 @@ void StubCode::GenerateZeroArgsUnoptimizedStaticCallStub(Assembler* assembler) {
   const intptr_t count_offset = ICData::CountIndexFor(0) * kWordSize;
 
   if (FLAG_optimization_counter_threshold >= 0) {
-    // Increment count for this call, ignore overflow.
-    __ addl(Address(EBX, count_offset), Immediate(Smi::RawValue(1)));
+    // Increment count for this call.
+    __ movl(EAX, Address(EBX, count_offset));
+    __ addl(EAX, Immediate(Smi::RawValue(1)));
+    __ movl(EDI, Immediate(Smi::RawValue(Smi::kMaxValue)));
+    __ cmovno(EDI, EAX);
+    __ StoreIntoSmiField(Address(EBX, count_offset), EDI);
   }
 
   // Load arguments descriptor into EDX.