Added fix for mozbz#1321579

firefox.spec

@@ -98,7 +98,7 @@ ExcludeArch: armv7hl
 Summary:        Mozilla Firefox Web browser
 Name:           firefox
 Version:        51.0.1
-Release:        5%{?pre_tag}%{?dist}
+Release:        6%{?pre_tag}%{?dist}
 URL:            https://www.mozilla.org/firefox/
 License:        MPLv1.1 or GPLv2+ or LGPLv2+
 Group:          Applications/Internet
@@ -145,6 +145,7 @@ Patch406:        mozilla-256180.patch
 # fix various rendering problems
 Patch407:        widget-rebase.patch
 Patch408:        mozilla-1319374.patch
+Patch409:        mozilla-1321579.patch
 
 # Debian patches
 Patch500:        mozilla-440908.patch
@@ -295,6 +296,7 @@ cd %{tarballdir}
 %patch407 -p1 -b .widget-rebase
 # ppc64 build fix
 %patch408 -p1 -b .1319374
+%patch409 -p1 -b .1321579
 
 # Debian extension patch
 %patch500 -p1 -b .440908
@@ -788,6 +790,9 @@ gtk-update-icon-cache %{_datadir}/icons/hicolor &>/dev/null || :
 #---------------------------------------------------------------------
 
 %changelog
+* Thu Feb 23 2017 Martin Stransky <stransky@redhat.com> - 51.0.1-6
+- Added fix for mozbz#1321579
+
 * Thu Feb 23 2017 Martin Stransky <stransky@redhat.com> - 51.0.1-5
 - Disabled -O3 optimization on rawhide to make FF usable (rhbz#1422532)
 

mozilla-1321579.patch

@@ -0,0 +1,39 @@
+diff --git a/build/autoconf/compiler-opts.m4 b/build/autoconf/compiler-opts.m4
+--- a/build/autoconf/compiler-opts.m4
++++ b/build/autoconf/compiler-opts.m4
+@@ -173,16 +173,34 @@ AC_SUBST([LD_IS_BFD])
+ 
+ if test "$GNU_CC"; then
+     if test -z "$DEVELOPER_OPTIONS"; then
+         CFLAGS="$CFLAGS -ffunction-sections -fdata-sections"
+         CXXFLAGS="$CXXFLAGS -ffunction-sections -fdata-sections"
+     fi
+     CFLAGS="$CFLAGS -fno-math-errno"
+     CXXFLAGS="$CXXFLAGS -fno-exceptions -fno-math-errno"
++
++    if test -z "$CLANG_CC"; then
++        case "$CC_VERSION" in
++        4.*)
++            ;;
++        *)
++            # Lifetime Dead Store Elimination level 2 (default in GCC6+) breaks Gecko.
++            # Ideally, we'd use -flifetime-dse=1, but that means we'd forcefully
++            # enable it on optimization levels where it would otherwise not be enabled.
++            # So we disable it entirely. But since that would mean inconsistency with
++            # GCC5, which has level 1 depending on optimization level, disable it on
++            # GCC5 as well, because better safe than sorry.
++            # Add it first so that a mozconfig can override by setting CFLAGS/CXXFLAGS.
++            CFLAGS="-fno-lifetime-dse $CFLAGS"
++            CXXFLAGS="-fno-lifetime-dse $CXXFLAGS"
++            ;;
++        esac
++    fi
+ fi
+ 
+ dnl ========================================================
+ dnl = Identical Code Folding
+ dnl ========================================================
+ 
+ MOZ_ARG_DISABLE_BOOL(icf,
+ [  --disable-icf          Disable Identical Code Folding],
+