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

runtime/vm/stub_code_arm.cc

Index: runtime/vm/stub_code_arm.cc
diff --git a/runtime/vm/stub_code_arm.cc b/runtime/vm/stub_code_arm.cc
index b36d832c9f3bc6d72ac5bb2a97f721b1c14b8cd8..8b8d8e2e7848dc069c9146c92cc3367d20832673 100644
--- a/runtime/vm/stub_code_arm.cc
+++ b/runtime/vm/stub_code_arm.cc
@@ -1339,10 +1339,11 @@ static void EmitFastSmiOp(Assembler* assembler,
   __ Bind(&ok);
 #endif
   if (FLAG_optimization_counter_threshold >= 0) {
-    // Update counter, ignore overflow.
+    // Update counter.
     const intptr_t count_offset = ICData::CountIndexFor(num_args) * kWordSize;
     __ LoadFromOffset(kWord, R1, R8, count_offset);
     __ adds(R1, R1, Operand(Smi::RawValue(1)));
+    __ LoadImmediate(R1, Smi::RawValue(Smi::kMaxValue), VS);  // Overflow.
     __ StoreIntoSmiField(Address(R8, count_offset), R1);
   }
   __ Ret();
@@ -1366,7 +1367,7 @@ void StubCode::GenerateNArgsCheckInlineCacheStub(
     Token::Kind kind,
     bool optimized) {
   __ CheckCodePointer();
-  ASSERT(num_args == 1 || num_args == 2);
+  ASSERT(num_args > 0);
 #if defined(DEBUG)
   {
     Label ok;
@@ -1402,60 +1403,59 @@ void StubCode::GenerateNArgsCheckInlineCacheStub(
   // Load arguments descriptor into R4.
   __ ldr(R4, FieldAddress(R9, ICData::arguments_descriptor_offset()));
   // Loop that checks if there is an IC data match.
-  Label loop, found, miss;
+  Label loop, update, test, found;
   // R9: IC data object (preserved).
   __ ldr(R8, FieldAddress(R9, ICData::ic_data_offset()));
   // R8: ic_data_array with check entries: classes and target functions.
-  const int kIcDataOffset = Array::data_offset() - kHeapObjectTag;
-  // R8: points at the IC data array.
+  __ AddImmediate(R8, R8, Array::data_offset() - kHeapObjectTag);
+  // R8: points directly to the first ic data array element.
 
   // Get the receiver's class ID (first read number of arguments from
   // arguments descriptor array and then access the receiver from the stack).
   __ ldr(NOTFP, FieldAddress(R4, ArgumentsDescriptor::count_offset()));
   __ sub(NOTFP, NOTFP, Operand(Smi::RawValue(1)));
+  __ ldr(R0, Address(SP, NOTFP, LSL, 1));  // NOTFP (argument_count - 1) is smi.
+  __ LoadTaggedClassIdMayBeSmi(R0, R0);
   // NOTFP: argument_count - 1 (smi).
+  // R0: receiver's class ID (smi).
+  __ ldr(R1, Address(R8, 0));  // First class id (smi) to check.
+  __ b(&test);
 
   __ Comment("ICData loop");
-
-  __ ldr(R0, Address(SP, NOTFP, LSL, 1));  // NOTFP (argument_count - 1) is Smi.
-  __ LoadTaggedClassIdMayBeSmi(R0, R0);
-  if (num_args == 2) {
-    __ sub(R1, NOTFP, Operand(Smi::RawValue(1)));
-    __ ldr(R1, Address(SP, R1, LSL, 1));  // R1 (argument_count - 2) is Smi.
-    __ LoadTaggedClassIdMayBeSmi(R1, R1);
-  }
-
-  // We unroll the generic one that is generated once more than the others.
-  bool optimize = kind == Token::kILLEGAL;
-
   __ Bind(&loop);
-  for (int unroll = optimize ? 4 : 2; unroll >= 0; unroll--) {
-    Label update;
-
-    __ ldr(R2, Address(R8, kIcDataOffset));
-    __ cmp(R0, Operand(R2));  // Class id match?
-    if (num_args == 2) {
-      __ b(&update, NE);  // Continue.
-      __ ldr(R2, Address(R8, kIcDataOffset + kWordSize));
-      __ cmp(R1, Operand(R2));  // Class id match?
+  for (int i = 0; i < num_args; i++) {
+    if (i > 0) {
+      // If not the first, load the next argument's class ID.
+      __ AddImmediate(R0, NOTFP, Smi::RawValue(-i));
+      __ ldr(R0, Address(SP, R0, LSL, 1));
+      __ LoadTaggedClassIdMayBeSmi(R0, R0);
+      // R0: next argument class ID (smi).
+      __ LoadFromOffset(kWord, R1, R8, i * kWordSize);
+      // R1: next class ID to check (smi).
     }
-    __ b(&found, EQ);  // Break.
-
-    __ Bind(&update);
-
-    const intptr_t entry_size =
-        ICData::TestEntryLengthFor(num_args) * kWordSize;
-    __ AddImmediate(R8, entry_size);  // Next entry.
-
-    __ CompareImmediate(R2, Smi::RawValue(kIllegalCid));  // Done?
-    if (unroll == 0) {
-      __ b(&loop, NE);
+    __ cmp(R0, Operand(R1));  // Class id match?
+    if (i < (num_args - 1)) {
+      __ b(&update, NE);  // Continue.
     } else {
-      __ b(&miss, EQ);
+      // Last check, all checks before matched.
+      __ b(&found, EQ);  // Break.
     }
   }
+  __ Bind(&update);
+  // Reload receiver class ID.  It has not been destroyed when num_args == 1.
+  if (num_args > 1) {
+    __ ldr(R0, Address(SP, NOTFP, LSL, 1));
+    __ LoadTaggedClassIdMayBeSmi(R0, R0);
+  }
+
+  const intptr_t entry_size = ICData::TestEntryLengthFor(num_args) * kWordSize;
+  __ AddImmediate(R8, entry_size);  // Next entry.
+  __ ldr(R1, Address(R8, 0));       // Next class ID.
+
+  __ Bind(&test);
+  __ CompareImmediate(R1, Smi::RawValue(kIllegalCid));  // Done?
+  __ b(&loop, NE);
 
-  __ Bind(&miss);
   __ Comment("IC miss");
   // Compute address of arguments.
   // NOTFP: argument_count - 1 (smi).
@@ -1494,14 +1494,14 @@ void StubCode::GenerateNArgsCheckInlineCacheStub(
   // R8: 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;
-  __ LoadFromOffset(kWord, R0, R8, kIcDataOffset + target_offset);
+  __ LoadFromOffset(kWord, R0, R8, target_offset);
 
   if (FLAG_optimization_counter_threshold >= 0) {
     __ Comment("Update caller's counter");
-    __ LoadFromOffset(kWord, R1, R8, kIcDataOffset + count_offset);
-    // Ignore overflow.
+    __ LoadFromOffset(kWord, R1, R8, count_offset);
     __ adds(R1, R1, Operand(Smi::RawValue(1)));
-    __ StoreIntoSmiField(Address(R8, kIcDataOffset + count_offset), R1);
+    __ LoadImmediate(R1, Smi::RawValue(Smi::kMaxValue), VS);  // Overflow.
+    __ StoreIntoSmiField(Address(R8, count_offset), R1);
   }
 
   __ Comment("Call target");
@@ -1627,9 +1627,10 @@ 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.
+    // Increment count for this call.
     __ LoadFromOffset(kWord, R1, R8, count_offset);
     __ adds(R1, R1, Operand(Smi::RawValue(1)));
+    __ LoadImmediate(R1, Smi::RawValue(Smi::kMaxValue), VS);  // Overflow.
     __ StoreIntoSmiField(Address(R8, count_offset), R1);
   }