Fix PowerPC ICE due to secondary_reload ignoring reload replacements

The reason for this PR is that insns emitted by secondary reload
patterns are being generated without taking into account other reloads
that may have occurred.  We run into this problem when an insn has a
pseudo that doesn't get a hard reg, and the pseudo is used in a way
that requires a secondary reload.  In this case the secondary reload
is needed due to gcc generating a 64-bit gpr load from memory insn
with an address offset not a multiple of 4.

	PR target/67378
	* config/rs6000/rs6000.c (rs6000_secondary_reload_gpr): Find
	reload replacement for PRE_MODIFY address reg.

From-SVN: r227573

gcc/ChangeLog

+2015-09-09  Alan Modra  <amodra@gmail.com>
+
+	PR target/67378
+	* config/rs6000/rs6000.c (rs6000_secondary_reload_gpr): Find
+	reload replacement for PRE_MODIFY address reg.
+
 2015-09-09  Sebastian Pop  <s.pop@samsung.com>
 
 	PR tree-optimization/53852

gcc/config/rs6000/rs6000.c

@@ -18198,8 +18198,21 @@ rs6000_secondary_reload_gpr (rtx reg, rtx mem, rtx scratch, bool store_p)
 
   if (GET_CODE (addr) == PRE_MODIFY)
     {
+      gcc_assert (REG_P (XEXP (addr, 0))
+		  && GET_CODE (XEXP (addr, 1)) == PLUS
+		  && XEXP (XEXP (addr, 1), 0) == XEXP (addr, 0));
       scratch_or_premodify = XEXP (addr, 0);
-      gcc_assert (REG_P (scratch_or_premodify));
+      if (!HARD_REGISTER_P (scratch_or_premodify))
+	/* If we have a pseudo here then reload will have arranged
+	   to have it replaced, but only in the original insn.
+	   Use the replacement here too.  */
+	scratch_or_premodify = find_replacement (&XEXP (addr, 0));
+
+      /* RTL emitted by rs6000_secondary_reload_gpr uses RTL
+	 expressions from the original insn, without unsharing them.
+	 Any RTL that points into the original insn will of course
+	 have register replacements applied.  That is why we don't
+	 need to look for replacements under the PLUS.  */
       addr = XEXP (addr, 1);
     }
   gcc_assert (GET_CODE (addr) == PLUS || GET_CODE (addr) == LO_SUM);