[PATCH v1 05/12] perf tests: Exercise data type resolution from a register

[Arnaldo Carvalho de Melo <acme@kernel.org>]

From: Arnaldo Carvalho de Melo <acme@redhat.com>

At -O2 a struct pointer lives in a register and DWARF describes it with
a register location, while the unoptimized workloads the data type tests
profile keep their variables on the stack.

Build a workload with a noinline function that gets the pointer from a
volatile global, which keeps it in a register, and check that its three
member accesses are resolved from that location.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/tests/shell/data_type_register.sh | 120 +++++++++++++++++++
 1 file changed, 120 insertions(+)
 create mode 100755 tools/perf/tests/shell/data_type_register.sh

diff --git a/tools/perf/tests/shell/data_type_register.sh b/tools/perf/tests/shell/data_type_register.sh
new file mode 100755
index 0000000000000000..e0369f076ae6f4b2
--- /dev/null
+++ b/tools/perf/tests/shell/data_type_register.sh
@@ -0,0 +1,120 @@
+#!/bin/bash
+# perf data type profiling tests for register variables
+# SPDX-License-Identifier: GPL-2.0
+
+set -e
+
+perfdata=$(mktemp /tmp/__perf_test.perf.data.XXXXX)
+perfout=$(mktemp /tmp/__perf_test.perf.out.XXXXX)
+prog=$(mktemp /tmp/__perf_test.regs.XXXXX)
+src="${prog}.c"
+
+cleanup()
+{
+	rm -f "$perfdata" "$perfout" "$prog" "$src"
+	trap - EXIT TERM INT
+}
+
+trap_cleanup()
+{
+	echo "Unexpected signal in ${FUNCNAME[1]}"
+	cleanup
+	exit 1
+}
+trap trap_cleanup EXIT TERM INT
+
+if ! perf check feature -q dwarf; then
+	echo "Skip: no DWARF (libdw) support"
+	cleanup
+	exit 2
+fi
+
+# No point in recording if the PMU cannot do memory events.
+if perf mem record -o /dev/null -- true 2>&1 | \
+		grep -q "failed: no PMU supports the memory events"; then
+	cleanup
+	exit 2
+fi
+if ! perf mem record -o /dev/null -- true 2>/dev/null; then
+	echo "Skip: cannot record memory events on this PMU"
+	cleanup
+	exit 2
+fi
+
+cat > "$src" <<'EOF'
+#include <signal.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+struct node {
+	long a;
+	long b;
+	long c;
+};
+
+static struct node n;
+static struct node *volatile vp;
+static volatile sig_atomic_t done;
+
+static void stop(int sig)
+{
+	done = 1;
+}
+
+__attribute__((noinline)) static long touch(struct node *p)
+{
+	long sum = 0;
+
+	sum += p->a;
+	p->b = sum;
+	sum += p->c;
+	return sum;
+}
+
+int main(void)
+{
+	unsigned long sum = 0;
+
+	vp = &n;
+	signal(SIGALRM, stop);
+	alarm(1);
+
+	while (!done)
+		sum += touch(vp);
+
+	return sum != 0;
+}
+EOF
+
+# -O2: the pointer stays in a register, so the accesses are resolved
+# from its type state instead of from a stack slot.
+if ! cc -O2 -g -fPIE -pie -o "$prog" "$src" 2>/dev/null; then
+	echo "Skip: cannot build the workload"
+	cleanup
+	exit 2
+fi
+
+if ! perf mem record -o "$perfdata" -- "$prog" > /dev/null 2>&1; then
+	echo "FAIL: perf mem record"
+	cleanup
+	exit 1
+fi
+
+if ! perf annotate --code-with-type -i "$perfdata" --stdio \
+		--percent-limit 1 > "$perfout" 2>/dev/null; then
+	echo "FAIL: perf annotate"
+	cleanup
+	exit 1
+fi
+
+for member in "+0 (a)" "+0x8 (b)" "+0x10 (c)"; do
+	if ! grep -Fq "# data-type: struct node ${member}" "$perfout"; then
+		echo "FAIL: member ${member} not resolved from the register"
+		cleanup
+		exit 1
+	fi
+done
+
+echo "register held access resolved"
+
+cleanup
-- 
2.56.0