2 files changed, 5 insertions, 5 deletions
diff --git a/.gitignore b/.gitignore
index 0166bb2..536c561 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,3 +14,4 @@ greybox_tmp/
 
 # ignores for the makefile build system
 waves/
+sims/
diff --git a/Makefile b/Makefile
index d97f6a0..dca5e74 100644
--- a/Makefile
+++ b/Makefile
@@ -2,9 +2,9 @@ IV        := iverilog
 IVFLAGS   := -g2005-sv
 
 SIM_SRCS  := $(wildcard *_tb.v)
-SIMS      := $(SIM_SRCS:.v=.sim)
+SIMS      := $(addprefix sims/,$(SIM_SRCS:.v=.sim))
 WAVES     := $(addprefix waves/,$(SIM_SRCS:.v=.vcd))
-DIRS      := waves
+DIRS      := sims waves
 
 DEPS                = $(sort $(1) $(foreach d,$(1),$(DEPS-$(d))))
 DEPS-alu           := $(call DEPS,shifter)
@@ -18,18 +18,17 @@ all: simulate
 simulate: $(WAVES)
 
 clean:
-	rm -f $(SIMS)
 	rm -rf $(DIRS)
 
 $(DIRS):
 	mkdir -p $@
 
-waves/%.vcd: %.sim | waves
+waves/%.vcd: sims/%.sim | waves
 	vvp $<
 
 .SECONDEXPANSION:
 pc := %
-%_tb.sim: %_tb.v %.v testbench.vh $$(patsubst $$(pc),$$(pc).v,$$(DEPS-$$*))
+sims/%_tb.sim: %_tb.v %.v testbench.vh $$(patsubst $$(pc),$$(pc).v,$$(DEPS-$$*)) | sims
 	$(IV) $(IVFLAGS) -o $@ $(filter-out %.vh,$^)
 
 .PHONY: all simulate clean