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RFA: Fix rtl-optimization/57439

Message ID 20130530050944.5a168ys5ggoggggs-nzlynne@webmail.spamcop.net
State New
Headers show

Commit Message

Joern Rennecke May 30, 2013, 9:09 a.m. UTC 
bootstrapped / regtested on i686-pc-linux-gnu
build / regtested for i686-pc-linux-gnu X sh-elf

Also, Andreas Schwab reported in the PR that he has successfully  
tested this patch on m68k.
2013-05-29  Joern Rennecke <joern.rennecke@embecosm.com>

	PR rtl-optimization/57439
	* postreload.c (move2add_valid_value_p): Check that we have
	a zero subreg_regno_offset when accessing the register in
	the requested mode.
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Patch

Index: postreload.c
===================================================================
--- postreload.c	(revision 199387)
+++ postreload.c	(working copy)
@@ -1726,10 +1726,25 @@  move2add_record_sym_value (rtx reg, rtx
 static bool
 move2add_valid_value_p (int regno, enum machine_mode mode)
 {
-  if (reg_set_luid[regno] <= move2add_last_label_luid
-      || !MODES_OK_FOR_MOVE2ADD (mode, reg_mode[regno]))
+  if (reg_set_luid[regno] <= move2add_last_label_luid)
     return false;
 
+  if (mode != reg_mode[regno])
+    {
+      if (!MODES_OK_FOR_MOVE2ADD (mode, reg_mode[regno]))
+	return false;
+      /* For big endian, the starting regno for the subreg might be
+	 different.  */
+      int s_off = subreg_lowpart_offset (mode, reg_mode[regno]);
+      s_off = subreg_regno_offset (regno, reg_mode[regno], s_off, mode);
+      if (s_off != 0)
+	/* We could in principle adjust regno, check reg_mode[regno] to be
+	   BLKmode, and return s_off to the caller (vs. -1 for failure),
+	   but we currently have no callers that could make use of this
+	   information.  */
+	return false;
+    }
+
   for (int i = hard_regno_nregs[regno][mode] - 1; i > 0; i--)
     if (reg_mode[regno + i] != BLKmode)
       return false;