diff --git a/.travis.yml b/.travis.yml
index 01d0c4721..6b4e8c3b6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,7 +17,24 @@ jobs:
   
     - stage: Test
       os: linux
-      before_install: 
+      dist: xenial
+      before_install:
+        - git clone https://github.com/steveicarus/ivtest.git
+        - export PATH=$HOME/bin:$PATH
+      script:
+        - autoconf
+        - ./configure --prefix=$HOME
+        - make install
+        - make check
+        - cd ivtest
+        - perl vvp_reg.pl
+        - diff regression_report-devel.txt regression_report.txt
+        - perl vpi_reg.pl
+
+    - stage: Test
+      os: linux
+      dist: bionic
+      before_install:
         - git clone https://github.com/steveicarus/ivtest.git
         - export PATH=$HOME/bin:$PATH
       script:
diff --git a/Makefile.in b/Makefile.in
index 5ac5515ac..974593374 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -254,12 +254,9 @@ lexor.o: lexor.cc parse.h
 
 parse.o: parse.cc
 
-# Build this in two steps to avoid parallel build issues (see pr3462585)
-parse.cc: $(srcdir)/parse.y
-	$(YACC) --verbose -t -p VL -d -o $@ $<
-parse.h: parse.cc
-	mv parse.cc.h $@ 2>/dev/null || mv parse.hh $@
-	touch $@
+# Use pattern rules to avoid parallel build issues (see pr3462585)
+parse%cc parse%h: $(srcdir)/parse%y
+	$(YACC) --verbose -t -p VL --defines=parse.h -o parse.cc $<
 
 syn-rules.cc: $(srcdir)/syn-rules.y
 	$(YACC) --verbose -t -p syn_ -o $@ $<
diff --git a/aclocal.m4 b/aclocal.m4
index a47eba42c..1b2dd6a1e 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -23,11 +23,13 @@ AC_SUBST(install_suffix)
 # ------------------------------
 # Sub-macro for AX_C_UNDERSCORES_LEADING and AX_C_UNDERSCORES_TRAILING.
 # Unwarranted assumptions:
-#   - the object file produced by AC_COMPILE_IFELSE is called "conftest.$ac_objext"
-#   - the nm(1) utility is available, and its name is "nm".
+#   - the object file produced by AC_COMPILE_IFELSE is called
+#     "conftest.$ac_objext"
+#   - the nm(1) utility or an equivalent is available, and its name
+#     is defined by the $NM variable.
 AC_DEFUN([_AX_C_UNDERSCORES_MATCH_IF],
 [AC_COMPILE_IFELSE([AC_LANG_SOURCE([void underscore(void){}])],
-[AS_IF([nm conftest.$ac_objext|grep $1 >/dev/null 2>/dev/null],[$2],[$3])],
+[AS_IF([$NM conftest.$ac_objext|grep $1 >/dev/null 2>/dev/null],[$2],[$3])],
 [AC_MSG_ERROR([underscore test crashed])]
 )])
 
diff --git a/driver/Makefile.in b/driver/Makefile.in
index 4d7144c5e..1cfdd7d8e 100644
--- a/driver/Makefile.in
+++ b/driver/Makefile.in
@@ -85,10 +85,9 @@ iverilog@EXEEXT@: $O
 cflexor.c: $(srcdir)/cflexor.lex
 	$(LEX) -s -t $< > $@
 
-# Build this in two steps to avoid parallel build issues (see pr3462585)
-cfparse.c: $(srcdir)/cfparse.y
-	$(YACC) --verbose -t -p cf -d -o $@ $<
-cfparse.h: cfparse.c
+# Use pattern rules to avoid parallel build issues (see pr3462585)
+cfparse%c cfparse%h: $(srcdir)/cfparse%y
+	$(YACC) --verbose -t -p cf -d -o cfparse.c $<
 
 %.o: %.c
 	$(CC) $(CPPFLAGS) $(CFLAGS) @DEPENDENCY_FLAG@ -c $< -o $*.o
diff --git a/tgt-pcb/Makefile.in b/tgt-pcb/Makefile.in
index a5f9b7d5b..5574fa781 100644
--- a/tgt-pcb/Makefile.in
+++ b/tgt-pcb/Makefile.in
@@ -88,11 +88,8 @@ fp_lex.o: fp_lex.cc fp.h
 fp_lex.cc: $(srcdir)/fp.lex
 	$(LEX) -s -ofp_lex.cc $(srcdir)/fp.lex
 
-fp.cc: $(srcdir)/fp.y
-	$(YACC) --verbose -t -p fp -d -o $@ $<
-fp.h: fp.cc
-	mv fp.cc.h $@ 2>/dev/null || mv fp.hh $@
-	touch $@
+fp%cc fp%h: $(srcdir)/fp%y
+	$(YACC) --verbose -t -p fp --defines=fp.h -o fp.cc $<
 
 ifeq (@WIN32@,yes)
   TGTLDFLAGS=-L.. -livl
diff --git a/vhdlpp/Makefile.in b/vhdlpp/Makefile.in
index 53ae140ae..2f808fc98 100644
--- a/vhdlpp/Makefile.in
+++ b/vhdlpp/Makefile.in
@@ -115,12 +115,9 @@ parse.o: parse.cc
 lexor.cc: $(srcdir)/lexor.lex
 	$(LEX) -s -olexor.cc $(srcdir)/lexor.lex
 
-# Build this in two steps to avoid parallel build issues (see pr3462585)
-parse.cc: $(srcdir)/parse.y
-	$(YACC) --verbose -t -d -o $@ $<
-parse.h: parse.cc
-	mv parse.cc.h $@ 2>/dev/null || mv parse.hh $@
-	touch $@
+# Use pattern rules to avoid parallel build issues (see pr3462585)
+parse%cc parse%h: $(srcdir)/parse%y
+	$(YACC) --verbose -t --defines=parse.h -o parse.cc $<
 
 lexor_keyword.o: lexor_keyword.cc parse.h
 
diff --git a/vpi/Makefile.in b/vpi/Makefile.in
index b08ba4244..818ac8347 100644
--- a/vpi/Makefile.in
+++ b/vpi/Makefile.in
@@ -149,20 +149,18 @@ sdf_lexor.o: sdf_lexor.c sdf_parse.h
 sdf_lexor.c: $(srcdir)/sdf_lexor.lex
 	$(LEX) -t $< > $@
 
-# Build this in two steps to avoid parallel build issues (see pr3462585)
-sdf_parse.c: $(srcdir)/sdf_parse.y
-	$(YACC) --verbose -t -p sdf -d -o $@ $<
-sdf_parse.h: sdf_parse.c
+# Use pattern rules to avoid parallel build issues (see pr3462585)
+sdf_parse%c sdf_parse%h: $(srcdir)/sdf_parse%y
+	$(YACC) --verbose -t -p sdf -d -o sdf_parse.c $<
 
 table_mod_lexor.o: table_mod_lexor.c table_mod_parse.h
 
 table_mod_lexor.c: $(srcdir)/table_mod_lexor.lex
 	$(LEX) -t $< > $@
 
-# Build this in two steps to avoid parallel build issues (see pr3462585)
-table_mod_parse.c: $(srcdir)/table_mod_parse.y
-	$(YACC) --verbose -t -p tblmod -d -o $@ $<
-table_mod_parse.h: table_mod_parse.c
+# Use pattern rules to avoid parallel build issues (see pr3462585)
+table_mod_parse%c table_mod_parse%h: $(srcdir)/table_mod_parse%y
+	$(YACC) --verbose -t -p tblmod -d -o table_mod_parse.c $<
 
 v2005_math.vpi: $(V2005) libvpi.a
 	$(CC) @shared@ -o $@ $(V2005) -L. $(LDFLAGS) -lvpi $(VA_MATH_VPI_LDFLAGS)
diff --git a/vvp/Makefile.in b/vvp/Makefile.in
index 8ccdb1d2e..14608b9eb 100644
--- a/vvp/Makefile.in
+++ b/vvp/Makefile.in
@@ -140,12 +140,9 @@ parse.o: parse.cc
 
 tables.o: tables.cc
 
-# Build this in two steps to avoid parallel build issues (see pr3462585)
-parse.cc: $(srcdir)/parse.y
-	$(YACC) --verbose -t -d -o $@ $<
-parse.h: parse.cc
-	mv parse.cc.h $@ 2>/dev/null || mv parse.hh $@
-	touch $@
+# Use pattern rules to avoid parallel build issues (see pr3462585)
+parse%cc parse%h: $(srcdir)/parse%y
+	$(YACC) --verbose -t --defines=parse.h -o parse.cc $<
 
 lexor.cc: $(srcdir)/lexor.lex
 	$(LEX) -s -olexor.cc $(srcdir)/lexor.lex