objtool: Remove instruction::list

Replace the instruction::list by allocating instructions in arrays of
256 entries and stringing them together by (amortized) find_insn().
This shrinks instruction by 16 bytes and brings it down to 128.

 struct instruction {
-	struct list_head           list;                 /*     0    16 */
-	struct hlist_node          hash;                 /*    16    16 */
-	struct list_head           call_node;            /*    32    16 */
-	struct section *           sec;                  /*    48     8 */
-	long unsigned int          offset;               /*    56     8 */
-	/* --- cacheline 1 boundary (64 bytes) --- */
-	long unsigned int          immediate;            /*    64     8 */
-	unsigned int               len;                  /*    72     4 */
-	u8                         type;                 /*    76     1 */
-
-	/* Bitfield combined with previous fields */
+	struct hlist_node          hash;                 /*     0    16 */
+	struct list_head           call_node;            /*    16    16 */
+	struct section *           sec;                  /*    32     8 */
+	long unsigned int          offset;               /*    40     8 */
+	long unsigned int          immediate;            /*    48     8 */
+	u8                         len;                  /*    56     1 */
+	u8                         prev_len;             /*    57     1 */
+	u8                         type;                 /*    58     1 */
+	s8                         instr;                /*    59     1 */
+	u32                        idx:8;                /*    60: 0  4 */
+	u32                        dead_end:1;           /*    60: 8  4 */
+	u32                        ignore:1;             /*    60: 9  4 */
+	u32                        ignore_alts:1;        /*    60:10  4 */
+	u32                        hint:1;               /*    60:11  4 */
+	u32                        save:1;               /*    60:12  4 */
+	u32                        restore:1;            /*    60:13  4 */
+	u32                        retpoline_safe:1;     /*    60:14  4 */
+	u32                        noendbr:1;            /*    60:15  4 */
+	u32                        entry:1;              /*    60:16  4 */
+	u32                        visited:4;            /*    60:17  4 */
+	u32                        no_reloc:1;           /*    60:21  4 */

-	u16                        dead_end:1;           /*    76: 8  2 */
-	u16                        ignore:1;             /*    76: 9  2 */
-	u16                        ignore_alts:1;        /*    76:10  2 */
-	u16                        hint:1;               /*    76:11  2 */
-	u16                        save:1;               /*    76:12  2 */
-	u16                        restore:1;            /*    76:13  2 */
-	u16                        retpoline_safe:1;     /*    76:14  2 */
-	u16                        noendbr:1;            /*    76:15  2 */
-	u16                        entry:1;              /*    78: 0  2 */
-	u16                        visited:4;            /*    78: 1  2 */
-	u16                        no_reloc:1;           /*    78: 5  2 */
+	/* XXX 10 bits hole, try to pack */

-	/* XXX 2 bits hole, try to pack */
-	/* Bitfield combined with next fields */
-
-	s8                         instr;                /*    79     1 */
-	struct alt_group *         alt_group;            /*    80     8 */
-	struct instruction *       jump_dest;            /*    88     8 */
-	struct instruction *       first_jump_src;       /*    96     8 */
+	/* --- cacheline 1 boundary (64 bytes) --- */
+	struct alt_group *         alt_group;            /*    64     8 */
+	struct instruction *       jump_dest;            /*    72     8 */
+	struct instruction *       first_jump_src;       /*    80     8 */
 	union {
-		struct symbol *    _call_dest;           /*   104     8 */
-		struct reloc *     _jump_table;          /*   104     8 */
-	};                                               /*   104     8 */
-	struct alternative *       alts;                 /*   112     8 */
-	struct symbol *            sym;                  /*   120     8 */
-	/* --- cacheline 2 boundary (128 bytes) --- */
-	struct stack_op *          stack_ops;            /*   128     8 */
-	struct cfi_state *         cfi;                  /*   136     8 */
+		struct symbol *    _call_dest;           /*    88     8 */
+		struct reloc *     _jump_table;          /*    88     8 */
+	};                                               /*    88     8 */
+	struct alternative *       alts;                 /*    96     8 */
+	struct symbol *            sym;                  /*   104     8 */
+	struct stack_op *          stack_ops;            /*   112     8 */
+	struct cfi_state *         cfi;                  /*   120     8 */

-	/* size: 144, cachelines: 3, members: 28 */
-	/* sum members: 142 */
-	/* sum bitfield members: 14 bits, bit holes: 1, sum bit holes: 2 bits */
-	/* last cacheline: 16 bytes */
+	/* size: 128, cachelines: 2, members: 29 */
+	/* sum members: 124 */
+	/* sum bitfield members: 22 bits, bit holes: 1, sum bit holes: 10 bits */
 };

pre:	5:38.18 real,   213.25 user,    124.90 sys,     23449040 mem
post:	5:03.34 real,   210.75 user,    88.80 sys,      20241232 mem

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org> # build only
Tested-by: Thomas Weißschuh <linux@weissschuh.net> # compile and run
Link: https://lore.kernel.org/r/20230208172245.851307606@infradead.org