@@ -4889,21 +4889,6 @@ if test "$plugins" = "yes" &&
"for this purpose. You can't build with --static."
fi
-########################################
-# See if __attribute__((alias)) is supported.
-# This false for Xcode 9, but has been remedied for Xcode 10.
-# Unfortunately, travis uses Xcode 9 by default.
-
-attralias=no
-cat > $TMPC << EOF
-int x = 1;
-extern const int y __attribute__((alias("x")));
-int main(void) { return 0; }
-EOF
-if compile_prog "" "" ; then
- attralias=yes
-fi
-
########################################
# check if getauxval is available.
@@ -5935,10 +5920,6 @@ if test "$atomic64" = "yes" ; then
echo "CONFIG_ATOMIC64=y" >> $config_host_mak
fi
-if test "$attralias" = "yes" ; then
- echo "CONFIG_ATTRIBUTE_ALIAS=y" >> $config_host_mak
-fi
-
if test "$getauxval" = "yes" ; then
echo "CONFIG_GETAUXVAL=y" >> $config_host_mak
fi
@@ -1944,6 +1944,24 @@ specific_ss.add(when: 'CONFIG_TCG', if_true: files(
))
specific_ss.add(when: 'CONFIG_TCG_INTERPRETER', if_true: files('tcg/tci.c'))
+# Work around a gcc bug/misfeature wherein constant propagation looks
+# through an alias:
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99696
+# to guess that a const variable is always zero. Without lto, this is
+# impossible, as the alias is restricted to page-vary-common.c. Indeed,
+# without lto, not even the alias is required -- we simply use different
+# declarations in different compilation units.
+pagevary = files('page-vary-common.c')
+if get_option('b_lto')
+ pagevary_flags = ['-fno-lto']
+ if get_option('cfi')
+ pagevary_flags += '-fno-sanitize=cfi-icall'
+ endif
+ pagevary = static_library('page-vary-common', sources: pagevary,
+ c_args: pagevary_flags)
+ pagevary = declare_dependency(link_with: pagevary)
+endif
+common_ss.add(pagevary)
specific_ss.add(files('page-vary.c'))
subdir('backends')
@@ -216,11 +216,7 @@ static inline void stl_phys_notdirty(AddressSpace *as, hwaddr addr, uint32_t val
#ifdef TARGET_PAGE_BITS_VARY
# include "exec/page-vary.h"
-#if defined(CONFIG_ATTRIBUTE_ALIAS) || !defined(IN_EXEC_VARY)
extern const TargetPageBits target_page;
-#else
-extern TargetPageBits target_page;
-#endif
#ifdef CONFIG_DEBUG_TCG
#define TARGET_PAGE_BITS ({ assert(target_page.decided); target_page.bits; })
#define TARGET_PAGE_MASK ({ assert(target_page.decided); \
@@ -26,4 +26,9 @@ typedef struct {
uint64_t mask;
} TargetPageBits;
+#ifdef IN_PAGE_VARY
+extern bool set_preferred_target_page_bits_common(int bits);
+extern void finalize_target_page_bits_common(int min);
+#endif
+
#endif /* EXEC_PAGE_VARY_H */
new file mode 100644
@@ -0,0 +1,54 @@
+/*
+ * Variable page size handling -- target independent part.
+ *
+ * Copyright (c) 2003 Fabrice Bellard
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define IN_PAGE_VARY 1
+
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "exec/page-vary.h"
+
+/* WARNING: This file must *not* be complied with -flto. */
+
+TargetPageBits target_page;
+
+bool set_preferred_target_page_bits_common(int bits)
+{
+ /*
+ * The target page size is the lowest common denominator for all
+ * the CPUs in the system, so we can only make it smaller, never
+ * larger. And we can't make it smaller once we've committed to
+ * a particular size.
+ */
+ if (target_page.bits == 0 || target_page.bits > bits) {
+ if (target_page.decided) {
+ return false;
+ }
+ target_page.bits = bits;
+ }
+ return true;
+}
+
+void finalize_target_page_bits_common(int min)
+{
+ if (target_page.bits == 0) {
+ target_page.bits = min;
+ }
+ target_page.mask = -1ull << target_page.bits;
+ target_page.decided = true;
+}
@@ -17,92 +17,25 @@
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
+#define IN_PAGE_VARY 1
+
#include "qemu/osdep.h"
#include "qemu-common.h"
-
-#define IN_EXEC_VARY 1
-
#include "exec/exec-all.h"
-#ifdef TARGET_PAGE_BITS_VARY
-# ifdef CONFIG_ATTRIBUTE_ALIAS
-/*
- * We want to declare the "target_page" variable as const, which tells
- * the compiler that it can cache any value that it reads across calls.
- * This avoids multiple assertions and multiple reads within any one user.
- *
- * This works because we finish initializing the data before we ever read
- * from the "target_page" symbol.
- *
- * This also requires that we have a non-constant symbol by which we can
- * perform the actual initialization, and which forces the data to be
- * allocated within writable memory. Thus "init_target_page", and we use
- * that symbol exclusively in the two functions that initialize this value.
- *
- * The "target_page" symbol is created as an alias of "init_target_page".
- */
-static TargetPageBits init_target_page;
-
-/*
- * Note that this is *not* a redundant decl, this is the definition of
- * the "target_page" symbol. The syntax for this definition requires
- * the use of the extern keyword. This seems to be a GCC bug in
- * either the syntax for the alias attribute or in -Wredundant-decls.
- *
- * See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91765
- */
-# pragma GCC diagnostic push
-# pragma GCC diagnostic ignored "-Wredundant-decls"
-
-extern const TargetPageBits target_page
- __attribute__((alias("init_target_page")));
-
-# pragma GCC diagnostic pop
-# else
-/*
- * When aliases are not supported then we force two different declarations,
- * by way of suppressing the header declaration with IN_EXEC_VARY.
- * We assume that on such an old compiler, LTO cannot be used, and so the
- * compiler cannot not detect the mismatched declarations, and all is well.
- */
-TargetPageBits target_page;
-# define init_target_page target_page
-# endif
-#endif
-
bool set_preferred_target_page_bits(int bits)
{
- /*
- * The target page size is the lowest common denominator for all
- * the CPUs in the system, so we can only make it smaller, never
- * larger. And we can't make it smaller once we've committed to
- * a particular size.
- */
#ifdef TARGET_PAGE_BITS_VARY
assert(bits >= TARGET_PAGE_BITS_MIN);
- if (init_target_page.bits == 0 || init_target_page.bits > bits) {
- if (init_target_page.decided) {
- return false;
- }
- init_target_page.bits = bits;
- }
-#endif
+ return set_preferred_target_page_bits_common(bits);
+#else
return true;
+#endif
}
void finalize_target_page_bits(void)
{
#ifdef TARGET_PAGE_BITS_VARY
- if (init_target_page.bits == 0) {
- init_target_page.bits = TARGET_PAGE_BITS_MIN;
- }
- init_target_page.mask = (target_long)-1 << init_target_page.bits;
- init_target_page.decided = true;
-
- /*
- * For the benefit of an -flto build, prevent the compiler from
- * hoisting a read from target_page before we finish initializing.
- */
- barrier();
+ finalize_target_page_bits_common(TARGET_PAGE_BITS_MIN);
#endif
}
@@ -118,6 +118,7 @@ S: Maintained
F: softmmu/cpus.c
F: cpus-common.c
F: page-vary.c
+F: page-vary-common.c
F: accel/tcg/
F: accel/stubs/tcg-stub.c
F: util/cacheinfo.c