Patch by Craig Schlenter. See http://codereview.chromium.org/118153

Change stack alignment on linux to 16 bytes to keep gcc 4.4 happy. 
This fixes the mksnapshot segfault without requiring -fno-tree-vectorize
which just avoided the problem by not generating code with movdqa.


git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2107 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

SConstruct

@@ -44,10 +44,10 @@ if ANDROID_TOP is None:
   ANDROID_TOP=""
 
 # TODO: Sort these issues out properly but as a temporary solution for gcc 4.4
-# on linux we need these compiler flags to avoid a mksnapshot segfault, avoid
-# crashes in the v8 test suite and avoid dtoa.c strict aliasing issues
+# on linux we need these compiler flags to avoid crashes in the v8 test suite
+# and avoid dtoa.c strict aliasing issues
 if os.environ.get('GCC_VERSION') == '44':
-    GCC_EXTRA_CCFLAGS = ['-fno-tree-vectorize', '-fno-tree-vrp']
+    GCC_EXTRA_CCFLAGS = ['-fno-tree-vrp']
     GCC_DTOA_EXTRA_CCFLAGS = ['-fno-strict-aliasing']
 else:
     GCC_EXTRA_CCFLAGS = []

src/platform-linux.cc

@@ -88,10 +88,15 @@ double OS::nan_value() {
 
 
 int OS::ActivationFrameAlignment() {
-  // Floating point code runs faster if the stack is 8-byte aligned.
+#ifdef V8_TARGET_ARCH_ARM
   // On EABI ARM targets this is required for fp correctness in the
   // runtime system.
   return 8;
+#else
+  // With gcc 4.4 the tree vectorization optimiser can generate code
+  // that requires 16 byte alignment such as movdqa on x86.
+  return 16;
+#endif
 }
 
 

tools/gyp/v8.gyp

@@ -307,8 +307,6 @@
                 'cflags': [
                     # Avoid gcc 4.4 strict aliasing issues in dtoa.c
                     '-fno-strict-aliasing',
-                    # Avoid gcc 4.4 mksnapshot segfault.
-                    '-fno-tree-vectorize',
                     # Avoid crashes with gcc 4.4 in the v8 test suite.
                     '-fno-tree-vrp',
                 ],