rust: Add an option to disable LTO for Rust
This adds an option to disable LTO when building a Rust module. This is
mostly intended to speedu p local prototyping, and LTO should not
normally be disabled for production builds.
Bug: 339628497
Test: m blueprint_tests && m rust
Change-Id: I21d5d4513a259a56f101ce8906e2bef7404e4efb
diff --git a/rust/builder.go b/rust/builder.go
index abbf90d..1ce92f4 100644
--- a/rust/builder.go
+++ b/rust/builder.go
@@ -158,7 +158,9 @@
func TransformSrcToBinary(ctx ModuleContext, mainSrc android.Path, deps PathDeps, flags Flags,
outputFile android.WritablePath) buildOutput {
- flags.GlobalRustFlags = append(flags.GlobalRustFlags, "-C lto=thin")
+ if ctx.RustModule().compiler.Thinlto() {
+ flags.GlobalRustFlags = append(flags.GlobalRustFlags, "-C lto=thin")
+ }
return transformSrctoCrate(ctx, mainSrc, deps, flags, outputFile, getTransformProperties(ctx, "bin"))
}
@@ -212,20 +214,28 @@
func TransformSrctoDylib(ctx ModuleContext, mainSrc android.Path, deps PathDeps, flags Flags,
outputFile android.WritablePath) buildOutput {
- flags.GlobalRustFlags = append(flags.GlobalRustFlags, "-C lto=thin")
+ if ctx.RustModule().compiler.Thinlto() {
+ flags.GlobalRustFlags = append(flags.GlobalRustFlags, "-C lto=thin")
+ }
return transformSrctoCrate(ctx, mainSrc, deps, flags, outputFile, getTransformProperties(ctx, "dylib"))
}
func TransformSrctoStatic(ctx ModuleContext, mainSrc android.Path, deps PathDeps, flags Flags,
outputFile android.WritablePath) buildOutput {
- flags.GlobalRustFlags = append(flags.GlobalRustFlags, "-C lto=thin")
+ if ctx.RustModule().compiler.Thinlto() {
+ flags.GlobalRustFlags = append(flags.GlobalRustFlags, "-C lto=thin")
+ }
+
return transformSrctoCrate(ctx, mainSrc, deps, flags, outputFile, getTransformProperties(ctx, "staticlib"))
}
func TransformSrctoShared(ctx ModuleContext, mainSrc android.Path, deps PathDeps, flags Flags,
outputFile android.WritablePath) buildOutput {
- flags.GlobalRustFlags = append(flags.GlobalRustFlags, "-C lto=thin")
+ if ctx.RustModule().compiler.Thinlto() {
+ flags.GlobalRustFlags = append(flags.GlobalRustFlags, "-C lto=thin")
+ }
+
return transformSrctoCrate(ctx, mainSrc, deps, flags, outputFile, getTransformProperties(ctx, "cdylib"))
}
diff --git a/rust/compiler.go b/rust/compiler.go
index 5033fba..efc3dee 100644
--- a/rust/compiler.go
+++ b/rust/compiler.go
@@ -47,6 +47,7 @@
edition() string
features() []string
rustdoc(ctx ModuleContext, flags Flags, deps PathDeps) android.OptionalPath
+ Thinlto() bool
// Output directory in which source-generated code from dependencies is
// copied. This is equivalent to Cargo's OUT_DIR variable.
@@ -231,6 +232,15 @@
// If cargo_env_compat is true, sets the CARGO_PKG_VERSION env var to this value.
Cargo_pkg_version *string
+
+ // Control whether LTO is used for the final (Rust) linkage. This does not impact
+ // cross-language LTO.
+ Lto struct {
+ // Whether thin LTO should be enabled. By default this is true.
+ // LTO provides such a large code size benefit for Rust, this should always
+ // be enabled for production builds unless there's a clear need to disable it.
+ Thin *bool `android:"arch_variant"`
+ } `android:"arch_variant"`
}
type baseCompiler struct {
@@ -273,6 +283,11 @@
return false
}
+// Thin LTO is enabled by default.
+func (compiler *baseCompiler) Thinlto() bool {
+ return BoolDefault(compiler.Properties.Lto.Thin, true)
+}
+
func (compiler *baseCompiler) SetDisabled() {
panic("baseCompiler does not implement SetDisabled()")
}
diff --git a/rust/compiler_test.go b/rust/compiler_test.go
index 89f4d1a..4caa12b 100644
--- a/rust/compiler_test.go
+++ b/rust/compiler_test.go
@@ -63,6 +63,35 @@
}
}
+func TestLtoFlag(t *testing.T) {
+ ctx := testRust(t, `
+ rust_library_host {
+ name: "libfoo",
+ srcs: ["foo.rs"],
+ crate_name: "foo",
+ lto: {
+ thin: false,
+ }
+ }
+
+ rust_library_host {
+ name: "libfoo_lto",
+ srcs: ["foo.rs"],
+ crate_name: "foo",
+ }
+ `)
+
+ libfoo := ctx.ModuleForTests("libfoo", "linux_glibc_x86_64_dylib").Rule("rustc")
+ libfooLto := ctx.ModuleForTests("libfoo_lto", "linux_glibc_x86_64_dylib").Rule("rustc")
+
+ if strings.Contains(libfoo.Args["rustcFlags"], "-C lto=thin") {
+ t.Fatalf("libfoo expected to disable lto -- rustcFlags: %#v", libfoo.Args["rustcFlags"])
+ }
+ if !strings.Contains(libfooLto.Args["rustcFlags"], "-C lto=thin") {
+ t.Fatalf("libfoo expected to enable lto by default -- rustcFlags: %#v", libfooLto.Args["rustcFlags"])
+ }
+}
+
// Test that we reject multiple source files.
func TestEnforceSingleSourceFile(t *testing.T) {