Add instret_overflow test

See riscv/riscv-isa-manual#1255

cc @Timmmm

Author: aswaterman

isa/rv32mi/Makefrag

@@ -17,5 +17,6 @@ rv32mi_sc_tests = \
 	sh-misaligned \
 	sw-misaligned \
 	zicntr \
+	instret_overflow \
 
 rv32mi_p_tests = $(addprefix rv32mi-p-, $(rv32mi_sc_tests))

isa/rv32mi/instret_overflow.S

@@ -0,0 +1,8 @@
+# See LICENSE for license details.
+
+#include "riscv_test.h"
+#undef RVTEST_RV64M
+#define RVTEST_RV64M RVTEST_RV32M
+#define __MACHINE_MODE
+
+#include "../rv64mi/instret_overflow.S"

isa/rv64mi/Makefrag

@@ -18,5 +18,6 @@ rv64mi_sc_tests = \
 	sw-misaligned \
 	sd-misaligned \
 	zicntr \
+	instret_overflow \
 
 rv64mi_p_tests = $(addprefix rv64mi-p-, $(rv64mi_sc_tests))

isa/rv64mi/instret_overflow.S

@@ -0,0 +1,42 @@
+# See LICENSE for license details.
+
+#*****************************************************************************
+# minstret_overflow.S
+#-----------------------------------------------------------------------------
+#
+# Test if overflow of instret is handled correctly
+#
+
+#include "riscv_test.h"
+#include "test_macros.h"
+
+RVTEST_RV64M
+RVTEST_CODE_BEGIN
+
+  # The value written to instret will be the value read by the following
+  # instruction (i.e. the increment is suppressed)
+  TEST_CASE(2, a0, 0, csrwi minstret, 0; csrr a0, minstret);
+
+#if __riscv_xlen == 32
+  # Writes to instreth are considered writes to instret and so also
+  # suppress the increment
+  TEST_CASE(3, a0, 0, li t0, 0xffffffff; csrw minstret, t0; csrw minstreth, t0; nop; csrr a0, minstret);
+  TEST_CASE(4, a0, 0, csrr a0, minstreth);
+#endif
+
+2:
+  TEST_PASSFAIL
+
+  .align 2
+  .global mtvec_handler
+mtvec_handler:
+  j fail
+
+RVTEST_CODE_END
+
+  .data
+RVTEST_DATA_BEGIN
+
+  TEST_DATA
+
+RVTEST_DATA_END