[PATCH ver 4] Fix hardware watchpoint check in test gdb.base/watchpoint-reuse-slot.exp

[Carl Love <cel@us.ibm.com>]

GDB maintainers:

Version 4:  Changed the test to use the variable
skip_hw_watchpoint_tests_p per Ulrich's comment.

Version 3:  I have updated the patch to use the
skip_hw_watchpoint_tests check instead of the
skip_hw_watchpoint_access_tests.  Also, I changed the patch to use the
same coding style as used in break-idempotent.exp per Ulrich's
comments.

The gdb.base/watchpoint-reuse-slot.exp uses the check:

if { ![target_info exists gdb,no_hardware_watchpoints]}

to determine if the test should be run with HW watchpoints.
The target_info exists check for HW watchpoints is TRUE on Power 9.
However HW watchpoints are disabled on Power 9 due to a HW bug. The
skip_hw_watchpoint_tests check needs to be used to properly determine
if HW watchpoints are supported by the processor.  If the processor is
PowerPC, the skip_hw_watchpoint_access_tests will run a small gdb test
if the processor supports HW watchpoints.   On other platforms, the
skip_hw_watchpoint_tests checks the list of processors that support HW
watchpoints.

This patch replaces the [target_info exists gdb,
no_hardware_watchpoints] with the skip_hw_watchpoint_tests
check to properly determine if the processor supports HW watchpoints.

The fix disables the HW watchpoint tests on Power 9 thus eliminating 48
testsuite failures.

The patch has been tested on Power 9, Power 10 and x86-64

Please let me know if this patch is acceptable for mainline.  Thanks.

                          Carl Love
----------------------

Fix hardware watchpoint check in test gdb.base/watchpoint-reuse-slot.exp

This test generates 48 failures on Power 9 when testing with HW watchpoints
enabled.  Note HW watchpoint support is disabled on Power 9 due to a HW bug.
The skip_hw_watchpoint_tests proc must be used to correctly determine
if the processor supports HW watchpoints.

This patch replaces the [target_info exists gdb,no_hardware_watchpoints]
with the skip_hw_watchpoint_tests check.

This patch was tested on Power 9, Power 10 and X86-64 with no regressions.
---
 gdb/testsuite/gdb.base/watchpoint-reuse-slot.exp | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/gdb/testsuite/gdb.base/watchpoint-reuse-slot.exp b/gdb/testsuite/gdb.base/watchpoint-reuse-slot.exp
index e2ea137424b..7ea6a7467c9 100644
--- a/gdb/testsuite/gdb.base/watchpoint-reuse-slot.exp
+++ b/gdb/testsuite/gdb.base/watchpoint-reuse-slot.exp
@@ -22,6 +22,16 @@
 # operation.  (Note that we don't have any of these watchpoints
 # trigger.)
 
+# The skip_hw_watchpoint_tests checks if watchpoints are supported by the
+# processor.  On PowerPC, the check runs a small test program under gdb
+# to determine if the Power processor supports HW watchpoints.  The check
+# must be done before starting the test so as to not disrupt the execution
+# of the actual test.
+
+set skip_hw_watchpoint_tests_p [skip_hw_watchpoint_tests]
+
+# starting the test.
+
 standard_testfile
 
 if {[prepare_for_testing "failed to prepare" $testfile $srcfile debug]} {
@@ -285,7 +295,7 @@ proc setup_and_run_watchpoints_tests { hw_wp_p } {
 
 # Run tests with hardware watchpoints disabled, then again with them
 # enabled (if this target supports hardware watchpoints).
-if { ![target_info exists gdb,no_hardware_watchpoints]} {
+if { !$skip_hw_watchpoint_tests_p } {
     # Run test with H/W enabled.
     setup_and_run_watchpoints_tests 1
 }
-- 
2.31.1