re PR rtl-optimization/78911 (Infinite loop at -O2/O3 optimization levels while…

re PR rtl-optimization/78911 (Infinite loop at -O2/O3 optimization levels while trying to compile server.c from Wine-2.0-rc2)

	PR rtl-optimization/78911
	* lra-assigns.c (must_not_spill_p): New function.
	(spill_for): Use it.

	PR rtl-optimization/78911
	* gcc.target/i386/pr78911-1.c: New test.
	* gcc.target/i386/pr78911-2.c: New test.

From-SVN: r246059

gcc/ChangeLog

+2017-03-10  Bernd Schmidt  <bschmidt@redhat.com>
+
+	PR rtl-optimization/78911
+	* lra-assigns.c (must_not_spill_p): New function.
+	(spill_for): Use it.
+
 2017-03-10  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/79981

gcc/lra-assigns.c

@@ -889,6 +889,30 @@ assign_temporarily (int regno, int hard_regno)
   live_pseudos_reg_renumber[regno] = hard_regno;
 }
 
+/* Return true iff there is a reason why pseudo SPILL_REGNO should not
+   be spilled.  */
+static bool
+must_not_spill_p (unsigned spill_regno)
+{
+  if ((pic_offset_table_rtx != NULL
+       && spill_regno == REGNO (pic_offset_table_rtx))
+      || ((int) spill_regno >= lra_constraint_new_regno_start
+	  && ! bitmap_bit_p (&lra_inheritance_pseudos, spill_regno)
+	  && ! bitmap_bit_p (&lra_split_regs, spill_regno)
+	  && ! bitmap_bit_p (&lra_subreg_reload_pseudos, spill_regno)
+	  && ! bitmap_bit_p (&lra_optional_reload_pseudos, spill_regno)))
+    return true;
+  /* A reload pseudo that requires a singleton register class should
+     not be spilled.
+     FIXME: this mitigates the issue on certain i386 patterns, but
+     does not solve the general case where existing reloads fully
+     cover a limited register class.  */
+  if (!bitmap_bit_p (&non_reload_pseudos, spill_regno)
+      && reg_class_size [reg_preferred_class (spill_regno)] == 1)
+    return true;
+  return false;
+}
+
 /* Array used for sorting reload pseudos for subsequent allocation
    after spilling some pseudo.	*/
 static int *sorted_reload_pseudos;
@@ -960,13 +984,7 @@ spill_for (int regno, bitmap spilled_pseudo_bitmap, bool first_p)
       /* Spill pseudos.	 */
       static_p = false;
       EXECUTE_IF_SET_IN_BITMAP (&spill_pseudos_bitmap, 0, spill_regno, bi)
-	if ((pic_offset_table_rtx != NULL
-	     && spill_regno == REGNO (pic_offset_table_rtx))
-	    || ((int) spill_regno >= lra_constraint_new_regno_start
-		&& ! bitmap_bit_p (&lra_inheritance_pseudos, spill_regno)
-		&& ! bitmap_bit_p (&lra_split_regs, spill_regno)
-		&& ! bitmap_bit_p (&lra_subreg_reload_pseudos, spill_regno)
-		&& ! bitmap_bit_p (&lra_optional_reload_pseudos, spill_regno)))
+	if (must_not_spill_p (spill_regno))
 	  goto fail;
 	else if (non_spilled_static_chain_regno_p (spill_regno))
 	  static_p = true;

gcc/testsuite/ChangeLog

+2017-03-10  Bernd Schmidt  <bschmidt@redhat.com>
+
+	PR rtl-optimization/78911
+	* gcc.target/i386/pr78911-1.c: New test.
+	* gcc.target/i386/pr78911-2.c: New test.
+
 2017-03-10  Will Schmidt <will_schmidt@vnet.ibm.com>
-    
+
 	PR target/79941
 	* gcc.target/powerpc/fold-vec-mult-even_odd_misc.c: New test.
 	* gcc.target/powerpc/fold-vec-mult-even_odd_char.c: New test.

gcc/testsuite/gcc.target/i386/pr78911-1.c

+/* PR rtl-optimization/78911 */
+/* { dg-do compile } */
+/* { dg-options "-O3 -fno-strict-aliasing -fno-omit-frame-pointer" } */
+/* { dg-additional-options "-fPIC" { target fpic } } */
+/* { dg-additional-options "-march=pentium-m" { target ia32 } } */
+
+int a, b, d, e;
+long long *c;
+
+static int
+foo (long long *x)
+{
+  return __sync_val_compare_and_swap (x, b, a);
+}
+
+void
+bar (void)
+{
+  if (!c)
+    return;
+  e = foo (&c[d]);
+}

gcc/testsuite/gcc.target/i386/pr78911-2.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-omit-frame-pointer" } */
+/* { dg-additional-options "-fPIC" { target fpic } } */
+/* { dg-additional-options "-march=i686" { target ia32 } } */
+
+long long *a, *b, c;
+int d, e;
+int baz (void);
+
+static inline long long
+foo (long long *x)
+{
+  return __sync_val_compare_and_swap (x, 0, 0);
+}
+
+void
+bar ()
+{
+  int f = baz ();
+  c = foo (&a[f]);
+  if (c)
+    e = d;
+  a = b;
+}