Revamp v8_optimized_debug options

build/toolchain.gypi

 # Copyright 2013 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 42 matching lines @@
     'v8_can_use_fpu_instructions%': 'true',
 
     # Similar to the ARM hard float ABI but on MIPS.
     'v8_use_mips_abi_hardfloat%': 'true',
 
     # Default arch variant for MIPS.
     'mips_arch_variant%': 'mips32r2',
 
     'v8_enable_backtrace%': 0,
 
-    # Turns on compiler optimizations in Debug builds (#defines are unaffected).
+    # Turns on compiler optimizations in Debug builds:
+    # 0 - optimizations off (default)
+    # 1 - basic optimizations on
+    # 3 - match release mode optimizations
     'v8_optimized_debug%': 0,
 
+    # #defines ENABLE_CHECK et al in Debug. On by default.
+    'v8_enable_checks_in_debug%': 1,
+
     # Enable profiling support. Only required on Windows.
     'v8_enable_prof%': 0,
 
     # Some versions of GCC 4.5 seem to need -fno-strict-aliasing.
     'v8_no_strict_aliasing%': 0,
 
     # Chrome needs this definition unconditionally. For standalone V8 builds,
     # it's handled in build/standalone.gypi.
     'want_separate_host_toolset%': 1,
 
@@ skipping 352 matching lines @@
       ['OS=="freebsd" or OS=="openbsd"', {
         'cflags': [ '-I/usr/local/include' ],
       }],
       ['OS=="netbsd"', {
         'cflags': [ '-I/usr/pkg/include' ],
       }],
     ],  # conditions
     'configurations': {
       'Debug': {
         'defines': [
-          'DEBUG',
           'ENABLE_DISASSEMBLER',
           'V8_ENABLE_CHECKS',
           'OBJECT_PRINT',
           'VERIFY_HEAP',

[Dirk Pranke, 2013/07/23 02:02:01]

Okay, from *initial* testing on linux, it looks like the main perf impact from
#defines between debug and release comes from defining DEBUG, not
V8_ENABLE_CHECKS or any of the other flags. (The time taken to run fast/html
drops from 30 seconds to 18).

[ I think that V8_ENABLE_CHECKS is still defined even if you #undef DEBUG, but I
need to double-check this (or have someone confirm). ]

At any rate, that means that really the thing that matters is changing from
DEBUG to NDEBUG, and we can leave V8_ENABLE_CHECKS always enabled in Debug mode.
Switching from -O1 to -O3 seems to maybe give an additional 5% boost. It's
unclear to me what the impact of this is on debuggability.

(again, this is *just* linux

         ],
         'msvs_settings': {
           'VCCLCompilerTool': {
             'conditions': [
               ['component=="shared_library"', {
                 'RuntimeLibrary': '3',  # /MDd
               }, {
                 'RuntimeLibrary': '1',  # /MTd
               }],
+              ['v8_optimized_debug==0', {
+                'Optimization': '0',
+              }],
               ['v8_optimized_debug==1', {
                 'Optimization': '1',
                 'InlineFunctionExpansion': '2',
                 'EnableIntrinsicFunctions': 'true',
                 'FavorSizeOrSpeed': '0',
                 'StringPooling': 'true',
                 'BasicRuntimeChecks': '0',
-              }, {
-                'Optimization': '0',
+              }],
+              ['v8_optimized_debug==3', {
+                'Optimization': '2',
+                'InlineFunctionExpansion': '2',
+                'EnableIntrinsicFunctions': 'true',
+                'FavorSizeOrSpeed': '0',
+                'StringPooling': 'true',
+                'BasicRuntimeChecks': '0',

[Dirk Pranke, 2013/07/23 02:02:01]

This was a flag missed on Windows that would cause compile errors there.

+                'conditions': [
+                  ['component=="shared_library"', {
+                    'RuntimeLibrary': '2',  #/MD
+                  }, {
+                    'RuntimeLibrary': '0',  #/MT
+                  }],
+                  ['v8_target_arch=="x64"', {
+                    # TODO(2207): remove this option once the bug is fixed.
+                    'WholeProgramOptimization': 'true',
+                  }],
+                ],
               }],
             ],
           },
           'VCLinkerTool': {
-            'LinkIncremental': '2',
+            'conditions': [
+              ['v8_optimized_debug==0', {
+                'LinkIncremental': '2',
+              }],
+              ['v8_optimized_debug==1', {
+                'LinkIncremental': '2',
+              }],
+              ['v8_optimized_debug==3', {
+                'LinkIncremental': '1',
+                'OptimizeReferences': '2',
+                'EnableCOMDATFolding': '2',
+              }],
+            ],
           },
         },
         'conditions': [
+          ['v8_enable_checks_in_debug==1', {
+            'defines': [
+              'DEBUG',
+            ],
+          }, {
+            'defines': [
+              'NDEBUG',
+            ],

[Dirk Pranke, 2013/07/23 02:02:01]

See comments above. This also means that 'v8_enable_checks_in_debug' is the
wrong name for this variable :), but I haven't fixed this yet.

+          }],
           ['OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="netbsd"', {
             'cflags': [ '-Wall', '<(werror)', '-W', '-Wno-unused-parameter',
                         '-Wnon-virtual-dtor', '-Woverloaded-virtual',
                         '<(wno_array_bounds)' ],
             'conditions': [
+              ['v8_optimized_debug==0', {
+                'cflags!': [
+                  '-O1',
+                  '-O2',
+                  '-O3',
+                  '-Os',
+                ],
+                'cflags': [
+                  '-O0',
+                ],
+              }],
               ['v8_optimized_debug==1', {
                 'cflags!': [
                   '-O0',
-                  '-O2',
+                  '-O3',
                   '-Os',
                 ],
                 'cflags': [
                   '-fdata-sections',
                   '-ffunction-sections',
                   '-O1',
                 ],
               }],
-              ['v8_optimized_debug==1 and gcc_version==44 and clang==0', {
+              ['v8_optimized_debug==3', {
+                'cflags!': [
+                  '-O0',
+                  '-O1',
+                  '-Os',
+                  '-g',
+                ],
+                'cflags': [
+                  '-fdata-sections',
+                  '-ffunction-sections',
+                  '-O3',
+                ],
+              }],
+              ['v8_optimized_debug!=0 and gcc_version==44 and clang==0', {
                 'cflags': [
                   # Avoid crashes with gcc 4.4 in the v8 test suite.
                   '-fno-tree-vrp',
                 ],
               }],
             ],
           }],
           ['OS=="linux" and v8_enable_backtrace==1', {
             # Support for backtrace_symbols.
             'ldflags': [ '-rdynamic' ],
           }],
           ['OS=="android"', {
             'variables': {
               'android_full_debug%': 1,
             },
             'conditions': [
               ['android_full_debug==0', {
                 # Disable full debug if we want a faster v8 in a debug build.
                 # TODO(2304): pass DISABLE_DEBUG_ASSERT instead of hiding DEBUG.
                 'defines!': [
                   'DEBUG',
                 ],
               }],
             ],
           }],
           ['OS=="mac"', {
             'xcode_settings': {
               'conditions': [
+                 ['v8_optimized_debug==0', {
+                   'GCC_OPTIMIZATION_LEVEL': '0',  # -O0
+                 }],
                  ['v8_optimized_debug==1', {
                    'GCC_OPTIMIZATION_LEVEL': '1',  # -O1
                    'GCC_STRICT_ALIASING': 'YES',
-                 }, {
-                   'GCC_OPTIMIZATION_LEVEL': '0',  # -O0
+                 }],
+                 ['v8_optimized_debug==3', {
+                   'GCC_OPTIMIZATION_LEVEL': '3',  # -O3
+                   'GCC_STRICT_ALIASING': 'YES',
                  }],
                ],
             },
           }],
         ],
       },  # Debug
       'Release': {
         'conditions': [
           ['OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="netbsd"', {
             'cflags!': [
@@ skipping 70 matching lines @@
                 'OptimizeReferences': '2',
                 'EnableCOMDATFolding': '2',
               },
             },
           }],  # OS=="win"
         ],  # conditions
       },  # Release
     },  # configurations
   },  # target_defaults
 }