parisc: Reduce kernel size by packing alternative tables

The values stored in the length and condition fields of the alternative
tables fit into 16 bits, so we can save 4 bytes per alternative table
entry.
Since a typical 32-bit kernel has more than 3000 entries this
saves > 12k of storage on disc.

bloat-o-meter shows a reduction of -0.01% by this change:
Total: Before=10196505, After=10195529, chg -0.01%

$ ls -la vmlinux vmlinux.before
-rwxr-xr-x  14437324 vmlinux
-rwxr-xr-x  14449512 vmlinux.before
Signed-off-by: Helge Deller <deller@gmx.de>

arch/parisc/include/asm/alternative.h

@@ -22,10 +22,10 @@
 
 struct alt_instr {
 	s32 orig_offset;	/* offset to original instructions */
-	s32 len;		/* end of original instructions */
-	u32 cond;		/* see ALT_COND_XXX */
+	s16 len;		/* end of original instructions */
+	u16 cond;		/* see ALT_COND_XXX */
 	u32 replacement;	/* replacement instruction or code */
-};
+} __packed;
 
 void set_kernel_text_rw(int enable_read_write);
 void apply_alternatives_all(void);
@@ -35,8 +35,9 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end,
 /* Alternative SMP implementation. */
 #define ALTERNATIVE(cond, replacement)		"!0:"	\
 	".section .altinstructions, \"aw\"	!"	\
-	".word (0b-4-.), 1, " __stringify(cond) ","	\
-		__stringify(replacement) "	!"	\
+	".word (0b-4-.)				!"	\
+	".hword 1, " __stringify(cond) "	!"	\
+	".word " __stringify(replacement) "	!"	\
 	".previous"
 
 #else
@@ -44,15 +45,17 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end,
 /* to replace one single instructions by a new instruction */
 #define ALTERNATIVE(from, to, cond, replacement)\
 	.section .altinstructions, "aw"	!	\
-	.word (from - .), (to - from)/4	!	\
-	.word cond, replacement		!	\
+	.word (from - .)		!	\
+	.hword (to - from)/4, cond	!	\
+	.word replacement		!	\
 	.previous
 
 /* to replace multiple instructions by new code */
 #define ALTERNATIVE_CODE(from, num_instructions, cond, new_instr_ptr)\
 	.section .altinstructions, "aw"	!	\
-	.word (from - .), -num_instructions !	\
-	.word cond, (new_instr_ptr - .)	!	\
+	.word (from - .)		!	\
+	.hword -num_instructions, cond	!	\
+	.word (new_instr_ptr - .)	!	\
 	.previous
 
 #endif  /*  __ASSEMBLY__  */

arch/parisc/kernel/alternative.c

@@ -26,7 +26,7 @@ void __init_or_module apply_alternatives(struct alt_instr *start,
 	struct alt_instr *entry;
 	int index = 0, applied = 0;
 	int num_cpus = num_online_cpus();
-	u32 cond_check;
+	u16 cond_check;
 
 	cond_check = ALT_COND_ALWAYS |
 		((num_cpus == 1) ? ALT_COND_NO_SMP : 0) |
@@ -45,8 +45,9 @@ void __init_or_module apply_alternatives(struct alt_instr *start,
 
 	for (entry = start; entry < end; entry++, index++) {
 
-		u32 *from, cond, replacement;
-		s32 len;
+		u32 *from, replacement;
+		u16 cond;
+		s16 len;
 
 		from = (u32 *)((ulong)&entry->orig_offset + entry->orig_offset);
 		len = entry->len;