Fix x86_64-ism in selftest (PR bootstrap/78705)

In r243317 I accidentally introduced an assumption in a selftest
in i386.c that Pmode == DImode.  This patch conditionalizes the
overzealous string comparison to avoid breaking the build on
32-bit i386.c targets.

gcc/ChangeLog:
	PR bootstrap/78705
	* config/i386/i386.c (selftest::ix86_test_dumping_memory_blockage):
	Conditionalize the string comparison on Pmode == DImode.

From-SVN: r243332

gcc/ChangeLog

+2016-12-06  David Malcolm  <dmalcolm@redhat.com>
+
+	PR bootstrap/78705
+	* config/i386/i386.c (ix86_test_dumping_memory_blockage):
+	Conditionalize the string comparison on Pmode == DImode.
+
 2016-12-06  Tom de Vries  <tom@codesourcery.com>
 
 	PR tree-optimization/67955

gcc/config/i386/i386.c

@@ -51190,12 +51190,14 @@ ix86_test_dumping_memory_blockage ()
 
   /* Verify that the repeated references to the SCRATCH show use
      reuse IDS.  The first should be prefixed with a reuse ID,
-     and the second should be dumped as a "reuse_rtx" of that ID.  */
-  ASSERT_RTL_DUMP_EQ_WITH_REUSE
-    ("(cinsn 1 (set (mem/v:BLK (0|scratch:DI) [0  A8])\n"
-     "        (unspec:BLK [\n"
-     "                (mem/v:BLK (reuse_rtx 0) [0  A8])\n"
-     "            ] UNSPEC_MEMORY_BLOCKAGE)))\n", pat, &r);
+     and the second should be dumped as a "reuse_rtx" of that ID.
+     The expected string assumes Pmode == DImode.  */
+  if (Pmode == DImode)
+    ASSERT_RTL_DUMP_EQ_WITH_REUSE
+      ("(cinsn 1 (set (mem/v:BLK (0|scratch:DI) [0  A8])\n"
+       "        (unspec:BLK [\n"
+       "                (mem/v:BLK (reuse_rtx 0) [0  A8])\n"
+       "            ] UNSPEC_MEMORY_BLOCKAGE)))\n", pat, &r);
 }
 
 /* Run all target-specific selftests.  */