[OE-core] [PATCH v2 9/9] gcc: update compiler architecture to match gcc-runtime (armv6, armv7a)

[Peter A. Bigot]

The gcc-runtime recipe builds the gcc libraries including libstdc++ with
$TARGET_CC_ARCH flags, which include -march=FOO flags that affect
whether atomic instructions are available.  This causes an ABI
incompatibility when the compiler by default generates code for less
capable architectures.  For example, gcc-runtime libraries on a
Cortex-A8 are built with a different C++11/C++14 mutex implementation
than is used code compiled outside OE and without architecture-specific
flags.

This commit fixes the problem specifically for ABI issues related to
atomic instructions available in ARMV6 and subsequent architectures.
Other ABI incompatibilities may remain in other architectures.

See: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62100

Signed-off-by: Peter A. Bigot <pab at pabigot.com>
---
 meta/recipes-devtools/gcc/gcc-configure-common.inc | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/meta/recipes-devtools/gcc/gcc-configure-common.inc b/meta/recipes-devtools/gcc/gcc-configure-common.inc
index 71dce12..48fb799 100644
--- a/meta/recipes-devtools/gcc/gcc-configure-common.inc
+++ b/meta/recipes-devtools/gcc/gcc-configure-common.inc
@@ -64,6 +64,13 @@ EXTRA_OECONF_append_libc-uclibc = " --enable-__cxa_atexit"
 EXTRA_OECONF_append_mips64 = " --with-abi=64 --with-arch-64=mips64 --with-tune-64=mips64"
 EXTRA_OECONF_append_mips64el = " --with-abi=64 --with-arch-64=mips64 --with-tune-64=mips64"
 
+# ARMv6+ adds atomic instructions that affect the ABI in libraries built
+# with TUNE_CCARGS in gcc-runtime.  Make the compiler default to a
+# compatible architecture.  armv6 and armv7a cover the minimum tune
+# features used in OE.
+EXTRA_OECONF_append_armv6 = " --with-arch=armv6"
+EXTRA_OECONF_append_armv7a = " --with-arch=armv7-a"
+
 EXTRA_OECONF_GCC_FLOAT ??= ""
 CPPFLAGS = ""
 
-- 
1.8.5.5