objtool: Use sec_offset_hash() for insn_hash

In preparation for find_insn_containing(), change insn_hash to use
sec_offset_hash().

This actually reduces runtime; probably because mixing in the section
index reduces the collisions due to text sections all starting their
instructions at offset 0.

Runtime on vmlinux.o from 3.1 to 2.5 seconds.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200416115119.227240432@infradead.orgSigned-off-by: Ingo Molnar <mingo@kernel.org>

tools/objtool/check.c

@@ -34,9 +34,10 @@ struct instruction *find_insn(struct objtool_file *file,
 {
 	struct instruction *insn;
 
-	hash_for_each_possible(file->insn_hash, insn, hash, offset)
+	hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
 		if (insn->sec == sec && insn->offset == offset)
 			return insn;
+	}
 
 	return NULL;
 }
@@ -282,7 +283,7 @@ static int decode_instructions(struct objtool_file *file)
 			if (ret)
 				goto err;
 
-			hash_add(file->insn_hash, &insn->hash, insn->offset);
+			hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
 			list_add_tail(&insn->list, &file->insn_list);
 			nr_insns++;
 		}