builder: add test to check for changes in binary size

This test only applies when using the built-in LLVM version. This way,
we have a stable LLVM version to test against. Distribution versions of
LLVM (especially Debian) tend to be patched in a way that affect the
results.

3 files changed, 96 insertions, 0 deletions

diff --git a/.github/workflows/build-macos.yml b/.github/workflows/build-macos.yml
index 46b77a89a..3151ac563 100644
--- a/.github/workflows/build-macos.yml
+++ b/.github/workflows/build-macos.yml
@@ -87,6 +87,8 @@ jobs:
       - name: Build wasi-libc
         if: steps.cache-wasi-libc.outputs.cache-hit != 'true'
         run: make wasi-libc
+      - name: make gen-device
+        run: make -j3 gen-device
       - name: Test TinyGo
         shell: bash
         run: make test GOTESTFLAGS="-short"
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index b2a3be139..fd46e8d87 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -97,6 +97,8 @@ jobs:
       - name: Install wasmtime
         run: |
           scoop install wasmtime
+      - name: make gen-device
+        run: make -j3 gen-device
       - name: Test TinyGo
         shell: bash
         run: make test GOTESTFLAGS="-short"
diff --git a/builder/sizes_test.go b/builder/sizes_test.go
new file mode 100644
index 000000000..98f01184b
--- /dev/null
+++ b/builder/sizes_test.go
@@ -0,0 +1,92 @@
+package builder
+
+import (
+	"runtime"
+	"testing"
+	"time"
+
+	"github.com/tinygo-org/tinygo/compileopts"
+)
+
+var sema = make(chan struct{}, runtime.NumCPU())
+
+type sizeTest struct {
+	target     string
+	path       string
+	codeSize   uint64
+	rodataSize uint64
+	dataSize   uint64
+	bssSize    uint64
+}
+
+// Test whether code and data size is as expected for the given targets.
+// This tests both the logic of loadProgramSize and checks that code size
+// doesn't change unintentionally.
+//
+// If you find that code or data size is reduced, then great! You can reduce the
+// number in this test.
+// If you find that the code or data size is increased, take a look as to why
+// this is. It could be due to an update (LLVM version, Go version, etc) which
+// is fine, but it could also mean that a recent change introduced this size
+// increase. If so, please consider whether this new feature is indeed worth the
+// size increase for all users.
+func TestBinarySize(t *testing.T) {
+	if runtime.GOOS == "linux" && !hasBuiltinTools {
+		// Debian LLVM packages are modified a bit and tend to produce
+		// different machine code. Ideally we'd fix this (with some attributes
+		// or something?), but for now skip it.
+		t.Skip("Skip: using external LLVM version so binary size might differ")
+	}
+
+	// This is a small number of very diverse targets that we want to test.
+	tests := []sizeTest{
+		// microcontrollers
+		{"hifive1b", "examples/echo", 4556, 272, 0, 2252},
+		{"microbit", "examples/serial", 2680, 380, 8, 2256},
+		{"wioterminal", "examples/pininterrupt", 6109, 1455, 116, 6816},
+
+		// TODO: also check wasm. Right now this is difficult, because
+		// wasm binaries are run through wasm-opt and therefore the
+		// output varies by binaryen version.
+	}
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.target+"/"+tc.path, func(t *testing.T) {
+			t.Parallel()
+
+			// Build the binary.
+			options := compileopts.Options{
+				Target:        tc.target,
+				Opt:           "z",
+				Semaphore:     sema,
+				InterpTimeout: 60 * time.Second,
+				Debug:         true,
+				VerifyIR:      true,
+			}
+			target, err := compileopts.LoadTarget(&options)
+			if err != nil {
+				t.Fatal("could not load target:", err)
+			}
+			config := &compileopts.Config{
+				Options: &options,
+				Target:  target,
+			}
+			result, err := Build(tc.path, "", t.TempDir(), config)
+			if err != nil {
+				t.Fatal("could not build:", err)
+			}
+
+			// Check whether the size of the binary matches the expected size.
+			sizes, err := loadProgramSize(result.Executable, nil)
+			if err != nil {
+				t.Fatal("could not read program size:", err)
+			}
+			if sizes.Code != tc.codeSize || sizes.ROData != tc.rodataSize || sizes.Data != tc.dataSize || sizes.BSS != tc.bssSize {
+				t.Errorf("Unexpected code size when compiling: -target=%s %s", tc.target, tc.path)
+				t.Errorf("            code rodata   data    bss")
+				t.Errorf("expected: %6d %6d %6d %6d", tc.codeSize, tc.rodataSize, tc.dataSize, tc.bssSize)
+				t.Errorf("actual:   %6d %6d %6d %6d", sizes.Code, sizes.ROData, sizes.Data, sizes.BSS)
+			}
+		})
+	}
+}