Tests: Add tests for -fno-dfg-peephole* (#6606)

Fixes -fno-dfg-peeophole-right-leaning-assoc.

Fixes #6601

src/V3DfgPeephole.cpp

@@ -373,7 +373,11 @@ class V3DfgPeephole final : public DfgVisitor {
                 replace(vtxp, rootp);
                 changed = true;
                 vtxp = rootp;
+                continue;
             }
+
+            // If we didn't apply the change (pattern was disabled), break the loop
+            break;
         }
 
         return changed;

test_regress/t/t_dfg_peephole.py

@@ -11,6 +11,7 @@ import vltest_bootstrap
 
 test.scenarios('vlt_all')
 test.sim_time = 2000000
+test.top_filename = "t/t_dfg_peephole.v"
 
 if not os.path.exists(test.root + "/.git"):
     test.skip("Not in a git repository")
@@ -72,6 +73,16 @@ test.compile(verilator_flags2=[
 ])  # yapf:disable
 
 # Compile optimized - also builds executable
+
+extraArgs = []
+if test.name == "t_dfg_peephole_off_all":
+    extraArgs.append("-fno-dfg-peephole")
+if test.name == "t_dfg_peephole_off_each":
+    for opt in optimizations:
+        opt = opt.lower()
+        opt = re.sub(r"_", "-", opt)
+        extraArgs.append("-fno-dfg-peephole-" + opt)
+
 test.compile(verilator_flags2=[
     "--stats",
     "--build",
@@ -84,20 +95,23 @@ test.compile(verilator_flags2=[
     "--dump-dfg",  # To fill code coverage
     "-CFLAGS \"-I .. -I ../obj_ref\"",
     "../obj_ref/Vref__ALL.a",
-    "../../t/" + test.name + ".cpp"
-])  # yapf:disable
+    "../../t/t_dfg_peephole.cpp"
+] + extraArgs)  # yapf:disable
 
 
-def check(name):
+def check(name, enabled):
     name = name.lower()
     name = re.sub(r'_', ' ', name)
-    test.file_grep(test.obj_dir + "/obj_opt/Vopt__stats.txt",
-                   r'DFG\s+(pre inline|post inline|scoped) Peephole, ' + name + r'\s+([1-9]\d*)')
+    pattern = r'DFG\s+(pre inline|post inline|scoped) Peephole, ' + name + r'\s+([1-9]\d*)\s*$'
+    if enabled:
+        test.file_grep(test.obj_dir + "/obj_opt/Vopt__stats.txt", pattern)
+    else:
+        test.file_grep_not(test.obj_dir + "/obj_opt/Vopt__stats.txt", pattern)
 
 
 # Check all optimizations defined in
 for opt in optimizations:
-    check(opt)
+    check(opt, test.name == "t_dfg_peephole")
 
 test.file_grep_not(test.obj_dir + "/obj_opt/Vopt__stats.txt",
                    r'DFG.*non-representable.*\s[1-9]\d*$')

test_regress/t/t_dfg_peephole_off_all.py

@@ -0,0 +1,16 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2025 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+import runpy
+
+test.scenarios('vlt_all')
+
+runpy.run_path("t/t_dfg_peephole.py", globals())

test_regress/t/t_dfg_peephole_off_each.py

@@ -0,0 +1,16 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2025 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+import runpy
+
+test.scenarios('vlt_all')
+
+runpy.run_path("t/t_dfg_peephole.py", globals())

test_regress/t/t_dist_docs_options.py

@@ -30,8 +30,6 @@ Test_Waivers = [
     '-rr',  # Not testing; not requiring rr installation
     # Need testing:
     '-fconst',  # TODO breaks due to some needed V3Const steps
-    '-fdfg-peephole',  # Need test of -fno-...
-    '-fdfg-peephole-',  # Need test of -fno-...
 ]
 
 Sums = {}