diff --git a/Makefile b/Makefile
index 53bcbec..f4a35b0 100644
--- a/Makefile
+++ b/Makefile
@@ -36,6 +36,23 @@ LIB_IR := $(LIB_IR_SRCS:ir/%.c=out/%.o)
 
 ELC_EIR := out/elc.c.eir.c.gcc.exe
 
+help:
+	@echo ''
+	@echo '*** Building/testing everything is not recommneded ***'
+	@echo ''
+	@echo 'Instead, you can use following targets for target xxx:'
+	@echo ''
+	@echo '- `make build-xxx`: Compile all tests to xxx backend'
+	@echo '   (e.g., out/lisp.c.eir.xxx will be built from test/lisp.c)'
+	@echo '- `make test-xxx` or `make xxx`: Run tests for xxx backend'
+	@echo '   (e.g., out/lisp.c.eir.xxx.out.diff will be output)'
+	@echo '- `make test-full-xxx`: Run target/xxx.c on ELVM'
+	@echo '   (this checks if the target xxx can self-host)'
+	@echo ''
+	@echo 'Running all tests by `make test`, will take a lot of time/disk'
+	@echo ''
+	@exit 1
+
 all: test
 
 out/git_submodule.stamp: .git/index
diff --git a/target.mk b/target.mk
index 7a4a99a..08aa8a7 100644
--- a/target.mk
+++ b/target.mk
@@ -21,6 +21,7 @@ EXT := $(TARGET)
 $(eval CMD = $$(ELC) -$(TARGET) $$2 > $$1.tmp && chmod 755 $$1.tmp && mv $$1.tmp $$1)
 OUT.eir.$(TARGET) := $(SRCS:%=%.$(EXT))
 include build.mk
+build-$(TARGET): $(OUT.eir.$(TARGET))
 
 include clear_vars.mk
 
@@ -36,7 +37,8 @@ EXPECT := eir.out
 ACTUAL := eir.$(TARGET).out
 include diff.mk
 
-$(TARGET): $(DIFFS)
+test-$(TARGET): $(DIFFS)
+$(TARGET): test-$(TARGET)
 
 # Make sure elc.c.eir can create the same target.
 
@@ -54,6 +56,7 @@ ACTUAL := eir.elc.$(TARGET)
 include diff.mk
 
 elc-$(TARGET): $(DIFFS)
+test-full-$(TARGET): elc-$(TARGET)
 
 else