--- a/build/moz.configure/warnings.configure
+++ b/build/moz.configure/warnings.configure
@@ -93,18 +93,18 @@ check_and_add_gcc_warning('-Wno-error=ma
 check_and_add_gcc_warning('-Wno-error=deprecated-declarations')
 
 # false positives depending on optimization
 check_and_add_gcc_warning('-Wno-error=array-bounds')
 
 # can't get rid of those PGO warnings
 check_and_add_gcc_warning('-Wno-error=coverage-mismatch', when='MOZ_PGO')
 
-# false positives during PGO
-check_and_add_gcc_warning('-Wno-error=free-nonheap-object', when='MOZ_PGO')
+# false positives depending on optimizations
+check_and_add_gcc_warning('-Wno-error=free-nonheap-object')
 
 # catches format/argument mismatches with printf
 check_and_add_gcc_warning('-Wformat')
 
 # We use mix of both POSIX and Win32 printf format across the tree, so format
 # warnings are useless on mingw.
 check_and_add_gcc_warning('-Wno-format',
                           when=depends(target)(lambda t: t.kernel == 'WINNT'))

--- a/old-configure.in
+++ b/old-configure.in
@@ -883,17 +883,21 @@ case "$target" in
     if test -z "$CLANG_CC"; then
        MOZ_OPTIMIZE_FLAGS="-freorder-blocks -fno-reorder-functions $MOZ_OPTIMIZE_FLAGS"
     fi
     ;;
 
 *-*linux*)
     if test "$GNU_CC" -o "$GNU_CXX"; then
         MOZ_PGO_OPTIMIZE_FLAGS="-O3"
-        MOZ_OPTIMIZE_FLAGS="-Os"
+        if test -n "$MOZ_DEBUG"; then
+            MOZ_OPTIMIZE_FLAGS="-Os"
+        else
+            MOZ_OPTIMIZE_FLAGS="-O2"
+        fi
         if test -z "$CLANG_CC"; then
            MOZ_OPTIMIZE_FLAGS="-freorder-blocks $MOZ_OPTIMIZE_FLAGS"
         fi
     fi
 
     case "${target_cpu}" in
     alpha*)
         CFLAGS="$CFLAGS -mieee"