Scale invocation count by the number of BBs in the flow-graph of a method.

runtime/vm/flow_graph_compiler_ia32.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_IA32.
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 11 matching lines @@
 #include "vm/symbols.h"
 
 namespace dart {
 
 DEFINE_FLAG(bool, trap_on_deoptimization, false, "Trap on deoptimization.");
 DEFINE_FLAG(bool, unbox_mints, true, "Optimize 64-bit integer arithmetic.");
 DECLARE_FLAG(int, optimization_counter_threshold);
 DECLARE_FLAG(int, reoptimization_counter_threshold);
 DECLARE_FLAG(bool, enable_type_checks);
 DECLARE_FLAG(bool, enable_simd_inline);
+DEFINE_FLAG(int, optimization_counter_scale, 2270,

[Vyacheslav Egorov (Google), 2014/08/28 14:26:40]

Maybe use 100 * Math.pow(Math.PI, Math.E) here? :)

[Anders Johnsen, 2014/08/28 14:44:16]

I'm not sure - where do you get that "magic number 100" from??? :)

[srdjan, 2014/08/28 16:49:16]

The number is definitely wrong, it must be a typo and should be 2718.

[srdjan, 2014/08/28 17:39:10]

On a serious note: do specific number (2270) looks fragile? Do 2000 or 3000 make
a lot of difference? 

[Vyacheslav Egorov (Google), 2014/08/28 18:06:49]

I would like to clarify where 2270 came from: originally Anders suggested
quadratic scaling a*x^2 + b * x + c which did not make much sense to me --- so I
suggested to use 2270 instead which is the tangent of the line which intersects
lines x = 0 and y = 30000 in the same points as Anders'es parabola (essentially
it's a linear approximation of the same quadratic scaling which actually grows
faster on this interval).



On 2014/08/28 17:39:10, srdjan wrote:

[Anders Johnsen, 2014/08/29 07:11:37]

Yes, the quadratic scale came from Karl and I experimenting, but as Slava found,
the curve was very close to a line for our use-case range. I've found 2000 to
work just as well.

+            "The scale of invocation count, by size of the function.");
+DEFINE_FLAG(int, optimization_counter_start, 5000,
+            "The minimum invocation count for a function.");

[srdjan, 2014/08/28 17:39:10]

Maybe rename to min_optimization_counter_threshold?

[Anders Johnsen, 2014/08/29 07:11:37]

Done.

 
 
 FlowGraphCompiler::~FlowGraphCompiler() {
   // BlockInfos are zone-allocated, so their destructors are not called.
   // Verify the labels explicitly here.
   for (int i = 0; i < block_info_.length(); ++i) {
     ASSERT(!block_info_[i]->jump_label()->IsLinked());
     ASSERT(!block_info_[i]->jump_label()->HasNear());
   }
 }
@@ skipping 951 matching lines @@
 
     // Patch point is after the eventually inlined function object.
     entry_patch_pc_offset_ = assembler()->CodeSize();
 
     if (is_optimizing()) {
       // Reoptimization of an optimized function is triggered by counting in
       // IC stubs, but not at the entry of the function.
       __ cmpl(FieldAddress(function_reg, Function::usage_counter_offset()),
               Immediate(FLAG_reoptimization_counter_threshold));
     } else {
+      intptr_t basic_blocks = flow_graph().preorder().length();

[srdjan, 2014/08/28 17:39:10]

const

[Anders Johnsen, 2014/08/29 07:11:37]

Done.

+      ASSERT(basic_blocks > 0);
+      intptr_t limit = FLAG_optimization_counter_scale * basic_blocks +
+          FLAG_optimization_counter_start;

[srdjan, 2014/08/28 17:39:10]

const

[Anders Johnsen, 2014/08/29 07:11:37]

Cannot, I may reassign below.

+      if (limit > FLAG_optimization_counter_threshold) {
+        limit = FLAG_optimization_counter_threshold;
+      }
       __ incl(FieldAddress(function_reg, Function::usage_counter_offset()));
       __ cmpl(FieldAddress(function_reg, Function::usage_counter_offset()),
-              Immediate(FLAG_optimization_counter_threshold));
+              Immediate(limit));
     }
     ASSERT(function_reg == EDI);
     __ j(GREATER_EQUAL, &stub_code->OptimizeFunctionLabel());
   } else if (!flow_graph().IsCompiledForOsr()) {
     entry_patch_pc_offset_ = assembler()->CodeSize();
   }
   __ Comment("Enter frame");
   if (flow_graph().IsCompiledForOsr()) {
     intptr_t extra_slots = StackSize()
         - flow_graph().num_stack_locals()
@@ skipping 757 matching lines @@
   __ movups(reg, Address(ESP, 0));
   __ addl(ESP, Immediate(kFpuRegisterSize));
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32