[PATCH 5/7] MIPS/testsuite: Verify MIPS II CPU branch stepping

["Maciej W. Rozycki" <macro@orcam.me.uk>]

From: Maciej W. Rozycki <macro@globalfoundries.com>

Verify that breakpoints are correctly placed via `mips32_next_pc' while
single-stepping through MIPS II CPU branches.

Approved-by: Maciej W. Rozycki <macro@orcam.me.uk>
---
 gdb/testsuite/gdb.arch/mips-allow.exp.tcl |   25 ++++++++
 gdb/testsuite/gdb.arch/mips2-branch.c     |   86 ++++++++++++++++++++++++++++++
 gdb/testsuite/gdb.arch/mips2-branch.exp   |   30 ++++++++++
 3 files changed, 141 insertions(+)

gdb-mips2-next-pc-test.diff
Index: binutils-gdb/gdb/testsuite/gdb.arch/mips-allow.exp.tcl
===================================================================
--- binutils-gdb.orig/gdb/testsuite/gdb.arch/mips-allow.exp.tcl
+++ binutils-gdb/gdb/testsuite/gdb.arch/mips-allow.exp.tcl
@@ -59,3 +59,28 @@ proc allow_mips1_bal_tests {} {
 	    } \
 	{-Wa,-fatal-warnings -mno-mips16 -minterlink-compressed}]
 }
+
+# Check for MIPS II branch-likely support.  These instructions may be
+# absent, such as with MIPS I, MIPSr6, or MIPS16 compilations, or only
+# supported as assembler macros, such as with microMIPS compilations.
+# Make sure an actual BEQL machine instruction is produced and no macro
+# expanded.
+proc allow_mips2_branch_tests {} {
+    return [allow_target_tests "allow_mips2_branch_tests" \
+	"MIPS II branch support" "Illegal instruction" \
+	    {
+		int main() {
+		    asm volatile (
+			".set	push\n\t"
+			".set	noreorder\n\t"
+			".set	nomacro\n\t"
+			"beql	$0, $0, 0f\n\t"
+			" nop\n"
+			"0:\n\t"
+			".set	pop\n");
+		    return 0;
+		}
+	    } \
+	{-Wa,-fatal-warnings -mno-mips16 -mno-micromips
+	    -minterlink-compressed}]
+}
Index: binutils-gdb/gdb/testsuite/gdb.arch/mips2-branch.c
===================================================================
--- /dev/null
+++ binutils-gdb/gdb/testsuite/gdb.arch/mips2-branch.c
@@ -0,0 +1,86 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright (C) 2026 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 single-stepping through MIPS II branch instructions.  */
+
+int
+test_mips2_branch (void)
+{
+  /* Make 'err' available to the debugger to track the number of single
+     steps executed.  Use `volatile' to prevent the variable from being
+     optimized away.  */
+  volatile int err = -1;
+
+  int any = 0x55aa;
+  int mone = -1;
+  int zero = 0;
+  int one = 1;
+
+  asm volatile (
+	".macro	b_test op, args:vararg\n\t"
+	"\\op	\\args, 0f\n\t"
+	" nop\n\t"
+	"nop\n"
+	"0:\n\t"
+	".endm\n\t"
+
+	".set	push\n\t"
+	".set	noreorder\n\t"
+	".globl	step_start\n\t"
+	".type	step_start, @function\n"
+	"step_start:\n\t"			/* Units: steps.  */
+	"nop\n\t"				/* NOP:       1s  */
+	"b_test	beql, %[any], %[any]\n\t"	/* Taken:     1s  */
+	"b_test	beql, %[any], %[one]\n\t"	/* Not taken: 2s  */
+	"b_test	bnel, %[any], %[any]\n\t"	/* Not taken: 2s  */
+	"b_test	bnel, %[any], %[one]\n\t"	/* Taken:     1s  */
+	"b_test	bltzl, %[mone]\n\t"		/* Taken:     1s  */
+	"b_test	bltzl, %[zero]\n\t"		/* Not taken: 2s  */
+	"b_test	bltzl, %[one]\n\t"		/* Not taken: 2s  */
+	"b_test	blezl, %[mone]\n\t"		/* Taken:     1s  */
+	"b_test	blezl, %[zero]\n\t"		/* Taken:     1s  */
+	"b_test	blezl, %[one]\n\t"		/* Not taken: 2s  */
+	"b_test	bgezl, %[mone]\n\t"		/* Not taken: 2s  */
+	"b_test	bgezl, %[zero]\n\t"		/* Taken:     1s  */
+	"b_test	bgezl, %[one]\n\t"		/* Taken:     1s  */
+	"b_test	bgtzl, %[mone]\n\t"		/* Not taken: 2s  */
+	"b_test	bgtzl, %[zero]\n\t"		/* Not taken: 2s  */
+	"b_test	bgtzl, %[one]\n\t"		/* Taken:     1s  */
+	"b_test	bltzall, %[mone]\n\t"		/* Taken:     1s  */
+	"b_test	bltzall, %[zero]\n\t"		/* Not taken: 2s  */
+	"b_test	bltzall, %[one]\n\t"		/* Not taken: 2s  */
+	"b_test	bgezall, %[mone]\n\t"		/* Not taken: 2s  */
+	"b_test	bgezall, %[zero]\n\t"		/* Taken:     1s  */
+	"b_test	bgezall, %[one]\n\t"		/* Taken:     1s  */
+	"nop\n\t"				/* NOP:       1s  */
+	".globl	step_stop\n\t"			/* Total:    35s  */
+	".type	step_stop, @function\n"
+	"step_stop:\n\t"
+	".set pop\n"
+	:
+	: [mone] "r" (mone), [zero] "r" (zero), [one] "r" (one),
+	  [any] "r" (any)
+	: "$31");
+
+  return err;
+}
+
+int
+main (void)
+{
+  return test_mips2_branch ();
+}
Index: binutils-gdb/gdb/testsuite/gdb.arch/mips2-branch.exp
===================================================================
--- /dev/null
+++ binutils-gdb/gdb/testsuite/gdb.arch/mips2-branch.exp
@@ -0,0 +1,30 @@
+# Copyright (C) 2026 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 single-stepping through MIPS II branch instructions.
+
+require {istarget "mips*-*-*"}
+
+source $srcdir/$subdir/mips-allow.exp.tcl
+
+require allow_mips2_branch_tests
+
+standard_testfile
+
+set steps 35
+foreach flag {-mno-mips16 -mno-micromips -minterlink-compressed} {
+    lappend compile_flags "additional_flags=$flag"
+}
+source $srcdir/$subdir/mips-stepi.exp.tcl