The --optimize-for-size flag should imply a small semi-space

R=hpayer@chromium.org, mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/585523002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24069 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/flag-definitions.h

@@ -10,6 +10,12 @@
 // which can be included multiple times in different modes.  It expects to have
 // a mode defined before it's included.  The modes are FLAG_MODE_... below:
 
+#define DEFINE_IMPLICATION(whenflag, thenflag)              \
+  DEFINE_VALUE_IMPLICATION(whenflag, thenflag, true)
+
+#define DEFINE_NEG_IMPLICATION(whenflag, thenflag)          \
+  DEFINE_VALUE_IMPLICATION(whenflag, thenflag, false)
+
 // We want to declare the names of the variables for the header file.  Normally
 // this will just be an extern declaration, but for a readonly flag we let the
 // compiler make better optimizations by giving it the value.
@@ -45,11 +51,8 @@
 
 // We produce the code to set flags when it is implied by another flag.
 #elif defined(FLAG_MODE_DEFINE_IMPLICATIONS)
-#define DEFINE_IMPLICATION(whenflag, thenflag) \
-  if (FLAG_##whenflag) FLAG_##thenflag = true;
-
-#define DEFINE_NEG_IMPLICATION(whenflag, thenflag) \
-  if (FLAG_##whenflag) FLAG_##thenflag = false;
+#define DEFINE_VALUE_IMPLICATION(whenflag, thenflag, value) \
+  if (FLAG_##whenflag) FLAG_##thenflag = value;
 
 #else
 #error No mode supplied when including flags.defs
@@ -68,12 +71,8 @@
 #define FLAG_ALIAS(ftype, ctype, alias, nam)
 #endif
 
-#ifndef DEFINE_IMPLICATION
-#define DEFINE_IMPLICATION(whenflag, thenflag)
-#endif
-
-#ifndef DEFINE_NEG_IMPLICATION
-#define DEFINE_NEG_IMPLICATION(whenflag, thenflag)
+#ifndef DEFINE_VALUE_IMPLICATION
+#define DEFINE_VALUE_IMPLICATION(whenflag, thenflag, value)
 #endif
 
 #define COMMA ,
@@ -214,6 +213,8 @@ DEFINE_BOOL(optimize_for_size, false,
             "Enables optimizations which favor memory size over execution "
             "speed.")
 
+DEFINE_VALUE_IMPLICATION(optimize_for_size, max_semi_space_size, 1)
+
 // Flags for data representation optimizations
 DEFINE_BOOL(unbox_double_arrays, true, "automatically unbox arrays of doubles")
 DEFINE_BOOL(string_slices, true, "use string slices")
@@ -929,6 +930,7 @@ DEFINE_BOOL(enable_ool_constant_pool, V8_OOL_CONSTANT_POOL,
 #undef DEFINE_ARGS
 #undef DEFINE_IMPLICATION
 #undef DEFINE_NEG_IMPLICATION
+#undef DEFINE_VALUE_IMPLICATION
 #undef DEFINE_ALIAS_BOOL
 #undef DEFINE_ALIAS_INT
 #undef DEFINE_ALIAS_STRING

test/cctest/test-heap.cc

@@ -4379,7 +4379,7 @@ UNINITIALIZED_TEST(PromotionQueue) {
 
     // In this test we will try to overwrite the promotion queue which is at the
     // end of to-space. To actually make that possible, we need at least two
-    // semi-space pages and take advantage of fragementation.
+    // semi-space pages and take advantage of fragmentation.
     // (1) Grow semi-space to two pages.
     // (2) Create a few small long living objects and call the scavenger to
     // move them to the other semi-space.
@@ -4399,6 +4399,12 @@ UNINITIALIZED_TEST(PromotionQueue) {
     // Grow the semi-space to two pages to make semi-space copy overwrite the
     // promotion queue, which will be at the end of the second page.
     intptr_t old_capacity = new_space->TotalCapacity();
+
+    // If we are in a low memory config, we can't grow to two pages and we can't
+    // run this test. This also means the issue we are testing cannot arise, as
+    // there is no fragmentation.
+    if (new_space->IsAtMaximumCapacity()) return;
+
     new_space->Grow();
     CHECK(new_space->IsAtMaximumCapacity());
     CHECK(2 * old_capacity == new_space->TotalCapacity());