Re: HEADS UP: merged llvm/clang 3.4

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On 22 Mar 2014, at 16:02, Jakub Lach <[e-mail]> wrote:
> I'm now testing with CPUTYPE?=3Dcore2 which translates to =
-march=3Dcore2,=20
> however I would like to emphasize, that previously it was set as =
native,=20
> I was not forcing (faulty?) penryn march.=20
>=20
> It should just autodetect CPU features (at least that was how GCC =
worked
> iirc- it used multiple flags for all features detected, not a single =
march)?

Yes, it auto-detects, if you use -march=3Dnative.  If you have a Penryn,
you have SSE4.1 support, which is more than "plain" Core2 does, e.g.
SSSE3.


> ... core2 fails the same way, now I will try sans CPUTYPE.

After some sleuthing, it turns out this is a bug in boost, when 128-bit
types are represented as a struct.  See this upstream commit:

=
https://github.com/boostorg/atomic/commit/e4bde20f2eec0a51be14533871d2123b=
d2ab9cf3

To fix it, drop the attached patch in /usr/ports/devel/boost-libs/files.
I tried this with CPUTYPE=3Dpenryn, and it worked for me.

I have cc'd the boost port maintainers, so I hope they can add this
patch soon. :)

-Dimitry


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--- boost/atomic/detail/gcc-atomic.hpp.orig	2013-07-20 20:01:35.000000000 +0200
+++ boost/atomic/detail/gcc-atomic.hpp	2014-03-22 20:05:04.000000000 +0100
@@ -958,14 +958,16 @@
 
 public:
     BOOST_DEFAULTED_FUNCTION(base_atomic(void), {})
-    explicit base_atomic(value_type const& v) BOOST_NOEXCEPT : v_(0)
+    explicit base_atomic(value_type const& v) BOOST_NOEXCEPT
     {
+        memset(&v_, 0, sizeof(v_));
         memcpy(&v_, &v, sizeof(value_type));
     }
 
     void store(value_type const& v, memory_order order = memory_order_seq_cst) volatile BOOST_NOEXCEPT
     {
-        storage_type tmp = 0;
+        storage_type tmp;
+        memset(&tmp, 0, sizeof(tmp));
         memcpy(&tmp, &v, sizeof(value_type));
         __atomic_store_n(&v_, tmp, atomics::detail::convert_memory_order_to_gcc(order));
     }
@@ -980,7 +982,8 @@
 
     value_type exchange(value_type const& v, memory_order order = memory_order_seq_cst) volatile BOOST_NOEXCEPT
     {
-        storage_type tmp = 0;
+        storage_type tmp;
+        memset(&tmp, 0, sizeof(tmp));
         memcpy(&tmp, &v, sizeof(value_type));
         tmp = __atomic_exchange_n(&v_, tmp, atomics::detail::convert_memory_order_to_gcc(order));
         value_type res;
@@ -994,7 +997,9 @@
         memory_order success_order,
         memory_order failure_order) volatile BOOST_NOEXCEPT
     {
-        storage_type expected_s = 0, desired_s = 0;
+        storage_type expected_s, desired_s;
+        memset(&expected_s, 0, sizeof(expected_s));
+        memset(&desired_s, 0, sizeof(desired_s));
         memcpy(&expected_s, &expected, sizeof(value_type));
         memcpy(&desired_s, &desired, sizeof(value_type));
         const bool success = __atomic_compare_exchange_n(&v_, &expected_s, desired_s, false,
@@ -1010,7 +1015,9 @@
         memory_order success_order,
         memory_order failure_order) volatile BOOST_NOEXCEPT
     {
-        storage_type expected_s = 0, desired_s = 0;
+        storage_type expected_s, desired_s;
+        memset(&expected_s, 0, sizeof(expected_s));
+        memset(&desired_s, 0, sizeof(desired_s));
         memcpy(&expected_s, &expected, sizeof(value_type));
         memcpy(&desired_s, &desired, sizeof(value_type));
         const bool success = __atomic_compare_exchange_n(&v_, &expected_s, desired_s, true,

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