[PATCH 2/3] gdb/testsuite: Filter out some registers for riscv

[Andrew Burgess <andrew.burgess@embecosm.com>]

On riscv the cycle counter, and instructions retired counter CSRs are
read only, this causes problems in the gdb.base/callfuncs.exp test, as
the values in these CSRs change after an inferior call, the check that
no target registers have been modified then fails.

Luckily the test already has a mechanism in place for filtering out
registers that are modified (and can't be restored) by an inferior call,
so this commit adds the problem registers into this list for riscv.

In the future we may end up needing to filter out more CSRs, but right
now, for the targets I have access too, these are the only ones causing
problems.

gdb/testsuite/ChangeLog:

	* gdb.base/callfuncs.exp (fetch_all_registers): Add riscv register
	filter pattern.
---
 gdb/testsuite/ChangeLog              |  5 +++++
 gdb/testsuite/gdb.base/callfuncs.exp | 10 ++++++++++
 2 files changed, 15 insertions(+)

diff --git a/gdb/testsuite/gdb.base/callfuncs.exp b/gdb/testsuite/gdb.base/callfuncs.exp
index 94636938752..c5e39918c2a 100644
--- a/gdb/testsuite/gdb.base/callfuncs.exp
+++ b/gdb/testsuite/gdb.base/callfuncs.exp
@@ -285,6 +285,16 @@ proc fetch_all_registers {test} {
 	    }
 	    exp_continue
 	}
+	-re "^\(?:cycle\|instret\)\[ \t\]+\[^\r\n\]+\r\n" {
+	    if [istarget "riscv*-*-*"] {
+		# Filter out the cycle counter and instructions
+		# retired counter CSRs which are read-only, giving
+		# spurious differences.
+	    } else {
+		lappend all_registers_lines $expect_out(0,string)
+	    }
+	    exp_continue
+	}
 	-re "^\[^ \t\]+\[ \t\]+\[^\r\n\]+\r\n" {
 	    lappend all_registers_lines $expect_out(0,string)
 	    exp_continue
-- 
2.12.2