xs,am: add xsextra as supplementary test API specified for xs test suit

* Thus, no need to implement APIs in xsextra for nemu,qemu,native,etc.

am/arch/riscv64-xs.mk

@@ -15,10 +15,10 @@ AM_SRCS := noop/isa/riscv/trm.c \
            nemu/common/video.c \
            dummy/audio.c \
            noop/isa/riscv/instr.c \
-           dummy/mpe.c \
+           xs/isa/riscv/mpe.c \
            nemu/isa/riscv/boot/start.S
 
-CFLAGS  += -I$(AM_HOME)/am/src/nemu/include -DISA_H=\"riscv.h\"
+CFLAGS  += -I$(AM_HOME)/am/src/nemu/include -I$(AM_HOME)/am/src/xs/include -DISA_H=\"riscv.h\"
 
 ASFLAGS += -DMAINARGS=\"$(mainargs)\"
 .PHONY: $(AM_HOME)/am/src/nemu/common/mainargs.S

am/src/xs/include/xs.h

@@ -0,0 +1,11 @@
+#ifndef __XIANGSHAN_H__
+#define __XIANGSHAN_H__
+
+#include <am.h>
+#include <xsextra.h>
+#include <klib-macros.h>
+
+#include ISA_H // "x86.h", "mips32.h", ...
+
+#endif
+

am/src/xs/isa/riscv/mpe.c

@@ -0,0 +1,21 @@
+#include <xs.h>
+
+int _mpe_init(void (*entry)()) {
+  return 1;
+}
+
+int _ncpu() {
+  return 1;
+}
+
+int _cpu() {
+  return 0;
+}
+
+intptr_t _atomic_xchg(volatile intptr_t *addr, intptr_t newval) {
+  return 0;
+}
+
+intptr_t _atomic_add(volatile intptr_t *addr, intptr_t adder) {
+  return 0;
+}

am/xsextra.h

@@ -0,0 +1,23 @@
+/*
+ * Supplementary driver APIs for XiangShan test suit
+ */
+
+#ifndef __XSEXTRA_H__
+#define __XSEXTRA_H__
+
+#include <stdint.h>
+#include <stddef.h>
+#include ARCH_H // "arch/x86-qemu.h", "arch/native.h", ...
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// ================= Supplement MPE =================
+intptr_t _atomic_add(volatile intptr_t *addr, intptr_t adder);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

tests/amtest/include/amtest.h

@@ -2,6 +2,7 @@
 #define __AMUNIT_H__
 
 #include <am.h>
+#include <xsextra.h>
 #include <klib.h>
 #include <klib-macros.h>