Fix EQ_ATTR_ALT size calculation (PR bootstrap/87417)

"r264537: Change EQ_ATTR_ALT to support up to 64 alternatives" changed
the format of EQ_ATTR_ALT from ii to ww.  This broke the bootstrap on
32-bit systems, because the formula for rtx_code_size assumed that only
certain codes contain HOST_WIDE_INTs.  This did not surface on 64-bit
systems, because rtunion is 8 bytes anyway, but on 32-bit systems it's
only 4 bytes.  This resulted in out-of-bounds writes and memory
corruptions in genattrtab.

gcc/ChangeLog:

2018-09-25  Ilya Leoshkevich  <iii@linux.ibm.com>

	PR bootstrap/87417
	* rtl.c (rtx_code_size): Take into account that EQ_ATTR_ALT
	contains HOST_WIDE_INTs when computing its size.

From-SVN: r264556

gcc/ChangeLog

+2018-09-25  Ilya Leoshkevich  <iii@linux.ibm.com>
+
+	PR bootstrap/87417
+	* rtl.c (rtx_code_size): Take into account that EQ_ATTR_ALT
+	contains HOST_WIDE_INTs when computing its size.
+
 2018-09-24  Jim Wilson  <jimw@sifive.com>
 
 	PR target/87391

gcc/rtl.c

@@ -110,8 +110,7 @@ const enum rtx_class rtx_class[NUM_RTX_CODE] = {
 
 const unsigned char rtx_code_size[NUM_RTX_CODE] = {
 #define DEF_RTL_EXPR(ENUM, NAME, FORMAT, CLASS)				\
-  (((ENUM) == CONST_INT || (ENUM) == CONST_DOUBLE			\
-    || (ENUM) == CONST_FIXED || (ENUM) == CONST_WIDE_INT)		\
+  ((FORMAT)[0] == 'w'							\
    ? RTX_HDR_SIZE + (sizeof FORMAT - 1) * sizeof (HOST_WIDE_INT)	\
    : (ENUM) == REG							\
    ? RTX_HDR_SIZE + sizeof (reg_info)					\