re PR middle-end/4520 (cselib.c hash_rtx incorrectly hashes based on rtx address)

PR middle-end/4520
	PR bootstrap/28784
	* cselib.c (cselib_hash_rtx): Avoid hashing on the address of labels
	and symbols.  Instead use the implementation from cse.c's hash_rtx.

From-SVN: r116891

gcc/ChangeLog

@@ -1,3 +1,10 @@
+2006-09-12  Roger Sayle  <roger@eyesopen.com>
+
+	PR middle-end/4520
+	PR bootstrap/28784
+	* cselib.c (cselib_hash_rtx): Avoid hashing on the address of labels
+	and symbols.  Instead use the implementation from cse.c's hash_rtx.
+
 2006-09-12  Jan Hubicka  <jh@suse.cz>
 
 	PR rtl-optimization/28071

gcc/cselib.c

@@ -630,14 +630,28 @@ cselib_hash_rtx (rtx x, int create)
 
       /* Assume there is only one rtx object for any given label.  */
     case LABEL_REF:
-      hash
-	+= ((unsigned) LABEL_REF << 7) + (unsigned long) XEXP (x, 0);
+      /* We don't hash on the address of the CODE_LABEL to avoid bootstrap
+	 differences and differences between each stage's debugging dumps.  */
+      hash += (((unsigned int) LABEL_REF << 7)
+	       + CODE_LABEL_NUMBER (XEXP (x, 0)));
       return hash ? hash : (unsigned int) LABEL_REF;
 
     case SYMBOL_REF:
-      hash
-	+= ((unsigned) SYMBOL_REF << 7) + (unsigned long) XSTR (x, 0);
-      return hash ? hash : (unsigned int) SYMBOL_REF;
+      {
+	/* Don't hash on the symbol's address to avoid bootstrap differences.
+	   Different hash values may cause expressions to be recorded in
+	   different orders and thus different registers to be used in the
+	   final assembler.  This also avoids differences in the dump files
+	   between various stages.  */
+	unsigned int h = 0;
+	const unsigned char *p = (const unsigned char *) XSTR (x, 0);
+
+	while (*p)
+	  h += (h << 7) + *p++; /* ??? revisit */
+
+	hash += ((unsigned int) SYMBOL_REF << 7) + h;
+	return hash ? hash : (unsigned int) SYMBOL_REF;
+      }
 
     case PRE_DEC:
     case PRE_INC: