LoongArch: Use common function sign_extend64()

There exists a common function sign_extend64() to sign extend a 64-bit
value using specified bit as sign-bit in include/linux/bitops.h, it is
more efficient, let us use it and remove the arch-specific sign_extend()
under arch/loongarch.
Suggested-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/include/asm/inst.h

@@ -377,14 +377,6 @@ static inline bool unsigned_imm_check(unsigned long val, unsigned int bit)
 	return val < (1UL << bit);
 }
 
-static inline unsigned long sign_extend(unsigned long val, unsigned int idx)
-{
-	if (!is_imm_negative(val, idx + 1))
-		return ((1UL << idx) - 1) & val;
-	else
-		return ~((1UL << idx) - 1) | val;
-}
-
 #define DEF_EMIT_REG0I26_FORMAT(NAME, OP)				\
 static inline void emit_##NAME(union loongarch_instruction *insn,	\
 			       int offset)				\

arch/loongarch/kernel/alternative.c

@@ -74,7 +74,7 @@ static void __init_or_module recompute_jump(union loongarch_instruction *buf,
 	switch (src->reg0i26_format.opcode) {
 	case b_op:
 	case bl_op:
-		jump_addr = cur_pc + sign_extend((si_h << 16 | si_l) << 2, 27);
+		jump_addr = cur_pc + sign_extend64((si_h << 16 | si_l) << 2, 27);
 		if (in_alt_jump(jump_addr, start, end))
 			return;
 		offset = jump_addr - pc;
@@ -93,7 +93,7 @@ static void __init_or_module recompute_jump(union loongarch_instruction *buf,
 		fallthrough;
 	case beqz_op:
 	case bnez_op:
-		jump_addr = cur_pc + sign_extend((si_h << 16 | si_l) << 2, 22);
+		jump_addr = cur_pc + sign_extend64((si_h << 16 | si_l) << 2, 22);
 		if (in_alt_jump(jump_addr, start, end))
 			return;
 		offset = jump_addr - pc;
@@ -112,7 +112,7 @@ static void __init_or_module recompute_jump(union loongarch_instruction *buf,
 	case bge_op:
 	case bltu_op:
 	case bgeu_op:
-		jump_addr = cur_pc + sign_extend(si << 2, 17);
+		jump_addr = cur_pc + sign_extend64(si << 2, 17);
 		if (in_alt_jump(jump_addr, start, end))
 			return;
 		offset = jump_addr - pc;