MdePkg/BaseLib: BaseLib for LOONGARCH64 architecture.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4053

Add LoongArch LOONGARCH64 BaseLib functions.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Zhiguang Liu <zhiguang.liu@intel.com>

Signed-off-by: Chao Li <lichao@loongson.cn>
Co-authored-by: Baoqi Zhang <zhangbaoqi@loongson.cn>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>

MdePkg/Library/BaseLib/LoongArch64/SwitchStack.S

@@ -0,0 +1,39 @@
+#------------------------------------------------------------------------------
+#
+# InternalSwitchStackAsm for LoongArch
+#
+# Copyright (c) 2022, Loongson Technology Corporation Limited. All rights reserved.<BR>
+#
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+#------------------------------------------------------------------------------
+
+#define STORE   st.d    /* 64 bit mode regsave instruction */
+#define LOAD    ld.d    /* 64 bit mode regload instruction */
+#define RSIZE   8       /* 64 bit mode register size */
+
+ASM_GLOBAL ASM_PFX(InternalSwitchStackAsm)
+
+/**
+  This allows the caller to switch the stack and goes to the new entry point
+
+  @param  JumpBuffer    A pointer to CPU context buffer.
+**/
+
+ASM_PFX(InternalSwitchStackAsm):
+  LOAD    $ra, $a0, RSIZE * 11
+  LOAD    $s0, $a0, RSIZE * 0
+  LOAD    $s1, $a0, RSIZE * 1
+  LOAD    $s2, $a0, RSIZE * 2
+  LOAD    $s3, $a0, RSIZE * 3
+  LOAD    $s4, $a0, RSIZE * 4
+  LOAD    $s5, $a0, RSIZE * 5
+  LOAD    $s6, $a0, RSIZE * 6
+  LOAD    $s7, $a0, RSIZE * 7
+  LOAD    $s8, $a0, RSIZE * 8
+  LOAD    $sp, $a0, RSIZE * 9
+  LOAD    $fp, $a0, RSIZE * 10
+  LOAD    $a0, $sp, 0
+  LOAD    $a1, $sp, 8
+  jirl    $zero, $ra, 0
+  .end