diff --git a/Makefile b/Makefile
index c5bd5c05..ed56bef2 100644
--- a/Makefile
+++ b/Makefile
@@ -94,14 +94,9 @@ build/tgo: *.go
 	go build -o build/tgo -i .
 
 # Build IR with the Go compiler.
-build/%.bc: src/examples/% src/examples/%/*.go build/tgo src/runtime/*.go build/runtime-$(TARGET)-combined.bc
+build/%.o: src/examples/% src/examples/%/*.go build/tgo src/runtime/*.go build/runtime-$(TARGET)-combined.bc
 	./build/tgo $(TGOFLAGS) -runtime build/runtime-$(TARGET)-combined.bc -o $@ $(subst src/,,$<)
 
-# Compile and optimize bitcode file.
-build/%.o: build/%.bc
-	$(OPT) -Oz -enable-coroutines -o $< $<
-	$(LLC) -filetype=obj -o $@ $<
-
 # Compile C sources for the runtime.
 build/%.bc: src/runtime/%.c src/runtime/*.h
 	@mkdir -p build
diff --git a/compiler.go b/compiler.go
index 51516dad..4a3467c1 100644
--- a/compiler.go
+++ b/compiler.go
@@ -2787,21 +2787,28 @@ func (c *Compiler) ApplyFunctionSections() {
 	}
 }
 
-func (c *Compiler) Optimize(optLevel, sizeLevel int) {
+func (c *Compiler) Optimize(optLevel, sizeLevel int, inlinerThreshold uint) {
 	builder := llvm.NewPassManagerBuilder()
 	defer builder.Dispose()
 	builder.SetOptLevel(optLevel)
 	builder.SetSizeLevel(sizeLevel)
-	builder.UseInlinerWithThreshold(200) // TODO depend on opt level, and -Os
+	builder.UseInlinerWithThreshold(inlinerThreshold)
+	builder.AddCoroutinePassesToExtensionPoints()
 
+	// Run function passes for each function.
 	funcPasses := llvm.NewFunctionPassManagerForModule(c.mod)
 	defer funcPasses.Dispose()
 	builder.PopulateFunc(funcPasses)
+	funcPasses.InitializeFunc()
+	for fn := c.mod.FirstFunction(); !fn.IsNil(); fn = llvm.NextFunction(fn) {
+		funcPasses.RunFunc(fn)
+	}
+	funcPasses.FinalizeFunc()
 
+	// Run module passes.
 	modPasses := llvm.NewPassManager()
 	defer modPasses.Dispose()
 	builder.Populate(modPasses)
-
 	modPasses.Run(c.mod)
 }
 
diff --git a/main.go b/main.go
index e2a9a137..b98f567c 100644
--- a/main.go
+++ b/main.go
@@ -59,7 +59,9 @@ func Compile(pkgName, runtimePath, outpath, target string, printIR, dumpSSA bool
 	if err := c.Verify(); err != nil {
 		return err
 	}
-	//c.Optimize(2, 1) // -O2 -Os
+
+	// TODO: provide a flag to disable (most) optimizations.
+	c.Optimize(2, 2, 5) // -Oz params
 	if err := c.Verify(); err != nil {
 		return err
 	}