gdb: testsuite: Test whether PC register is expedited in gdb.server/server-run.exp

One thing GDB always does when the inferior stops is finding out where
it's stopped at, by way of querying the value of the program counter
register.

To save a packet round trip, the remote target can send the PC
value (often alongside other frequently consulted registers such as the
stack pointer) in the stop reply packet as an "expedited register".

Test that this is actually done for the targets where gdbserver is
supposed to.

Extend the "maintenance print remote-registers" command output with an
"Expedited" column which says "yes" if the register was seen by GDB in
the last stop reply packet it received, and is left blank otherwise.

Tested for regressions on aarch64-linux-gnu native-extended-remote.

The testcase was tested on aarch64-linux-gnu, i686-linux-gnu and
x86_64-linux-gnu native-remote and native-extended-remote targets.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Approved-By: Tom Tromey <tom@tromey.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.server/server-run.exp b/gdb/testsuite/gdb.server/server-run.exp
index 92eb38b..af5a5f5 100644
--- a/gdb/testsuite/gdb.server/server-run.exp
+++ b/gdb/testsuite/gdb.server/server-run.exp
@@ -52,3 +52,36 @@ if { [istarget *-*-linux*] } {
 
 gdb_breakpoint main
 gdb_test "continue" "Breakpoint.* main .*" "continue to main"
+
+if { [istarget "aarch64*-*-*"]
+     || [istarget "arm*-*-*"]
+     || [istarget "csky*-*-*"]
+     || [istarget "loongarch*-*-*"]
+     || [istarget "riscv*-*-*"] } {
+    set pc_regname "pc"
+} elseif { [is_amd64_regs_target] } {
+    set pc_regname "rip"
+} elseif { [is_x86_like_target] } {
+    set pc_regname "eip"
+} elseif { [istarget "tic6x-*-*"] } {
+    set pc_regname "PC"
+}
+
+# Sending the PC register in advance is good practice.  Test that this is
+# actually done for the targets where gdbserver is supposed to.
+set expedited_pc_test_name "send PC as expedited register in stop reply"
+if { [info exists pc_regname] } {
+    set seen_line false
+    gdb_test_multiple "maintenance print remote-registers" \
+	     $expedited_pc_test_name -lbl {
+	-re " ${pc_regname}\[\[:space:\]\]+${decimal}.*${decimal}  yes" {
+	    set seen_line true
+	    exp_continue
+	}
+	-re "\r\n$gdb_prompt $" {
+	    gdb_assert { $seen_line } $gdb_test_name
+	}
+    }
+} else {
+    untested $expedited_pc_test_name
+}