The following patch fixes
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56847
Reload pass is lucky choosing alternative without offsettable memory
in movti_internal pattern as this alternative for some reason has reject
value less by one than alternative with offsettable memory. LRA chooses
offsettable memory alternative as it looks cheaper and don't need
secondary reload in alternative chosen by reload pass (and reload pass
completely ignores this fact). LRA choice results in failure to
generate insns for reloading address to make it offsettable.
After several tries, I think I found a good solution for the problem.
The patch was successfully bootstrapped on x86 and x86-64 (with and
without -fpie). I tried 500K lines of test code and did not find any
difference in generated code using different options including -fpie.
So the patch will not affect huge majority of the code.
Committed as rev. 198101.
2013-04-19 Vladimir Makarov <vmaka...@redhat.com>
PR rtl-optimization/56847
* lra-constraints.c (process_alt_operands): Discourage alternative
with non-matche doffsettable memory constraint fro memory with
known offset.
2013-04-19 Vladimir Makarov <vmaka...@redhat.com>
PR rtl-optimization/56847
* gcc.dg/pr56847.c: New test.
Index: lra-constraints.c
===================================================================
--- lra-constraints.c (revision 198092)
+++ lra-constraints.c (working copy)
@@ -1978,8 +1978,15 @@ process_alt_operands (int only_alternati
(op, this_alternative) == NO_REGS))))
reject += LRA_MAX_REJECT;
- if (! ((const_to_mem && constmemok)
- || (MEM_P (op) && offmemok)))
+ if (MEM_P (op) && offmemok)
+ {
+ /* If we know offset and this non-offsetable memory,
+ something wrong with this memory and it is better
+ to try other memory possibilities. */
+ if (MEM_OFFSET_KNOWN_P (op))
+ reject += LRA_MAX_REJECT;
+ }
+ else if (! (const_to_mem && constmemok))
{
/* We prefer to reload pseudos over reloading other
things, since such reloads may be able to be
Index: testsuite/gcc.dg/pr56847.c
===================================================================
--- testsuite/gcc.dg/pr56847.c (revision 0)
+++ testsuite/gcc.dg/pr56847.c (working copy)
@@ -0,0 +1,12 @@
+/* PR rtl-optimization/56847 */
+/* { dg-do compile { target pie } } */
+/* { dg-options "-O2 -fpie" } */
+
+struct S { long int a, b; } e;
+__thread struct S s;
+
+void
+foo (void)
+{
+ s = e;
+}
