[PATCH v2 2/2] gdb/testsuite: Add test for AArch64 Scalable Vector Extension

[Thiago Jung Bauermann via Gdb-patches <gdb-patches@sourceware.org>]

It exercises a bug that GDB previously had where it would lose track of
some registers when the inferior changed its vector length.

It also checks that the vg register and the size of the z0-z31 registers
correctly reflect the new vector length.
---
 gdb/testsuite/gdb.arch/aarch64-sve.c   |  64 ++++++++++++++++
 gdb/testsuite/gdb.arch/aarch64-sve.exp | 101 +++++++++++++++++++++++++
 gdb/testsuite/lib/gdb.exp              |   6 ++
 gdb/testsuite/lib/mi-support.exp       |   4 -
 4 files changed, 171 insertions(+), 4 deletions(-)
 create mode 100644 gdb/testsuite/gdb.arch/aarch64-sve.c
 create mode 100644 gdb/testsuite/gdb.arch/aarch64-sve.exp

diff --git a/gdb/testsuite/gdb.arch/aarch64-sve.c b/gdb/testsuite/gdb.arch/aarch64-sve.c
new file mode 100644
index 000000000000..916b5cd82b38
--- /dev/null
+++ b/gdb/testsuite/gdb.arch/aarch64-sve.c
@@ -0,0 +1,64 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2022 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* Exercise AArch64's Scalable Vector Extension.
+
+   This test was based on QEMU's sve-ioctls.c test file.  */
+
+#include <stdio.h>
+#include <sys/auxv.h>
+#include <sys/prctl.h>
+
+static int
+do_sve_ioctl_test (void)
+{
+  int i, res, init_vl;
+
+  res = prctl (PR_SVE_GET_VL, 0, 0, 0, 0);
+  if (res < 0)
+    {
+      printf ("FAILED to PR_SVE_GET_VL (%d)", res);
+      return -1;
+    }
+  init_vl = res & PR_SVE_VL_LEN_MASK;
+
+  for (i = init_vl; i > 15; i /= 2)
+    {
+      printf ("Checking PR_SVE_SET_VL=%d\n", i);
+      res = prctl (PR_SVE_SET_VL, i, 0, 0, 0, 0); /* break here */
+      if (res < 0)
+	{
+	  printf ("FAILED to PR_SVE_SET_VL (%d)", res);
+	  return -1;
+	}
+    }
+  return 0;
+}
+
+int
+main (int argc, char **argv)
+{
+  if (getauxval (AT_HWCAP) & HWCAP_SVE)
+    {
+      return do_sve_ioctl_test ();
+    }
+  else
+    {
+      printf ("SKIP: no HWCAP_SVE on this system\n");
+      return 1;
+    }
+}
diff --git a/gdb/testsuite/gdb.arch/aarch64-sve.exp b/gdb/testsuite/gdb.arch/aarch64-sve.exp
new file mode 100644
index 000000000000..803aae5fdfb2
--- /dev/null
+++ b/gdb/testsuite/gdb.arch/aarch64-sve.exp
@@ -0,0 +1,101 @@
+# Copyright 2022 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test a binary that uses SVE and exercise changing the SVE vector length.
+
+if {[skip_aarch64_sve_tests]} {
+    verbose "Skipping ${gdb_test_file_name}."
+    return
+}
+
+standard_testfile
+if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
+    return
+}
+
+set linespec ${srcfile}:[gdb_get_line_number "break here"]
+
+if ![runto ${linespec}] {
+    return
+}
+
+# Count number of lines in "info registers" output.
+proc count_info_registers {} {
+    global gdb_prompt
+    set ret 0
+
+    gdb_test_multiple "info all-registers" "" {
+	-re ".*$gdb_prompt $" {
+	    set ret [count_newlines $expect_out(buffer)]
+	}
+    }
+
+    return ${ret}
+}
+
+proc get_register_value {register} {
+    global gdb_prompt
+    set ret ""
+
+    gdb_test_multiple "print \$${register}" "" {
+	-re ". = \[0-9\]+\r\n$gdb_prompt $" {
+	    regexp {. = ([0-9]+)} $expect_out(buffer) matched ret
+	}
+	-re ".*$gdb_prompt $" {
+	}
+    }
+
+    return ${ret}
+}
+
+# The test executable halves the vector length in a loop, so loop along
+# to check it.
+for {set i [get_register_value "vg"]} {$i > 1} {set i [expr $i / 2]} {
+    set lines_before [count_info_registers]
+
+    gdb_test "next" ".*if .res < 0." "step over prctl vg = ${i}"
+
+    set lines_after [count_info_registers]
+
+    # There was a bug where GDB would lose track of some registers when the
+    # vector length changed.  Make sure they're still all there.
+    if {${lines_before} == ${lines_after}} {
+	pass "same number of registers vg = ${i}"
+    } else {
+	fail "same number of registers vg = ${i}"
+    }
+
+    gdb_test "print \$vg" ". = ${i}" "vg was changed to ${i}"
+
+    set size_after [expr {$i * 8}]
+
+    for {set j 0} {$j < 32} {set j [incr j]} {
+	gdb_test "print sizeof(\$z$j)" ". = ${size_after}" "z$j has ${size_after} bytes"
+    }
+
+    gdb_test_multiple "continue" "" {
+	-re ".*Breakpoint $decimal, do_sve_ioctl_test .*$gdb_prompt $" {
+	    # Next iteration.
+	}
+	-re "Inferior 1 .* exited normally.*$gdb_prompt $" {
+	    # We're done.
+	    break
+	}
+	-re "$gdb_prompt $" {
+	    fail "unexpected output"
+	    break;
+	}
+    }
+}
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index a8f25b5f0dd5..b6bfa8eaafa5 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -7885,6 +7885,12 @@ proc multi_line_input { args } {
     return [join $args "\n"]
 }
 
+# Return how many newlines there are in the given string.
+
+proc count_newlines { string } {
+    return [regexp -all "\n" $string]
+}
+
 # Return the version of the DejaGnu framework.
 #
 # The return value is a list containing the major, minor and patch version
diff --git a/gdb/testsuite/lib/mi-support.exp b/gdb/testsuite/lib/mi-support.exp
index ca56e12b06bf..e821c0f6914f 100644
--- a/gdb/testsuite/lib/mi-support.exp
+++ b/gdb/testsuite/lib/mi-support.exp
@@ -1728,10 +1728,6 @@ set mi_autotest_data ""
 # The name of the source file for autotesting.
 set mi_autotest_source ""
 
-proc count_newlines { string } {
-    return [regexp -all "\n" $string]
-}
-
 # Prepares for running inline tests in FILENAME.
 # See comments for mi_run_inline_test for detailed
 # explanation of the idea and syntax.