boost: Fix invalid const in atomic builtins

Fixes build with clang

(From OE-Core rev: b844cc9a3ac95f51586a57e973c1b3c4188b9cff)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 76 insertions, 0 deletions

diff --git a/meta/recipes-support/boost/boost/0001-Removed-clang-specific-branch-for-x86-DCAS-based-loa.patch b/meta/recipes-support/boost/boost/0001-Removed-clang-specific-branch-for-x86-DCAS-based-loa.patch
new file mode 100644
index 0000000000..182693079a
--- /dev/null
+++ b/meta/recipes-support/boost/boost/0001-Removed-clang-specific-branch-for-x86-DCAS-based-loa.patch
@@ -0,0 +1,76 @@
+From 39b027171e0a619d49b9dd2e8471d10b6c41bc25 Mon Sep 17 00:00:00 2001
+From: Andrey Semashev <andrey.semashev@gmail.com>
+Date: Tue, 17 Jul 2018 12:37:29 +0300
+Subject: [PATCH] Removed clang-specific branch for x86 DCAS-based loads.
+
+The storage to load from is const-qualified and DCAS via compiler intrinsics
+require an unqualified pointer. Use asm implementation instead, which should be
+as efficient as intrinsics, if not better, in this case.
+
+Fixes https://github.com/boostorg/atomic/issues/15.
+
+Upstream-Status: Backport [https://github.com/boostorg/atomic/commit/6e14ca24dab50ad4c1fa8c27c7dd6f1cb791b534]
+Signed-off-by: Khem Raj <raj.khem@gmail.com>
+---
+ boost/atomic/detail/ops_gcc_x86_dcas.hpp | 23 ++++++++++++-----------
+ 1 file changed, 12 insertions(+), 11 deletions(-)
+
+diff --git a/boost/atomic/detail/ops_gcc_x86_dcas.hpp b/boost/atomic/detail/ops_gcc_x86_dcas.hpp
+index 4dacc66f..b43ef23a 100644
+--- a/boost/atomic/detail/ops_gcc_x86_dcas.hpp
++++ b/boost/atomic/detail/ops_gcc_x86_dcas.hpp
+@@ -158,11 +158,13 @@ struct gcc_dcas_x86
+         }
+         else
+         {
+-#if defined(__clang__)
+-            // Clang cannot allocate eax:edx register pairs but it has sync intrinsics
+-            value = __sync_val_compare_and_swap(&storage, (storage_type)0, (storage_type)0);
+-#elif defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS)
++            // Note that despite const qualification cmpxchg8b below may issue a store to the storage. The storage value
++            // will not change, but this prevents the storage to reside in read-only memory.
++
++#if defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS)
++
+             uint32_t value_bits[2];
++
+             // We don't care for comparison result here; the previous value will be stored into value anyway.
+             // Also we don't care for ebx and ecx values, they just have to be equal to eax and edx before cmpxchg8b.
+             __asm__ __volatile__
+@@ -175,7 +177,9 @@ struct gcc_dcas_x86
+                 : BOOST_ATOMIC_DETAIL_ASM_CLOBBER_CC_COMMA "memory"
+             );
+             BOOST_ATOMIC_DETAIL_MEMCPY(&value, value_bits, sizeof(value));
++
+ #else // defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS)
++
+             // We don't care for comparison result here; the previous value will be stored into value anyway.
+             // Also we don't care for ebx and ecx values, they just have to be equal to eax and edx before cmpxchg8b.
+             __asm__ __volatile__
+@@ -187,6 +191,7 @@ struct gcc_dcas_x86
+                 : [storage] "m" (storage)
+                 : BOOST_ATOMIC_DETAIL_ASM_CLOBBER_CC_COMMA "memory"
+             );
++
+ #endif // defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS)
+         }
+ 
+@@ -401,15 +406,11 @@ struct gcc_dcas_x86_64
+ 
+     static BOOST_FORCEINLINE storage_type load(storage_type const volatile& storage, memory_order) BOOST_NOEXCEPT
+     {
+-#if defined(__clang__)
++        // Note that despite const qualification cmpxchg16b below may issue a store to the storage. The storage value
++        // will not change, but this prevents the storage to reside in read-only memory.
+ 
+-        // Clang cannot allocate rax:rdx register pairs but it has sync intrinsics
+-        storage_type value = storage_type();
+-        return __sync_val_compare_and_swap(&storage, value, value);
+-
+-#elif defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS)
++#if defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS)
+ 
+-        // Some compilers can't allocate rax:rdx register pair either and also don't support 128-bit __sync_val_compare_and_swap
+         uint64_t value_bits[2];
+ 
+         // We don't care for comparison result here; the previous value will be stored into value anyway.