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rust: Add an option to disable LTO for Rust

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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
This commit is contained in:
Ivan Lozano 2024-05-15 10:59:47 -04:00
parent e8fcd37775
commit ab58647b2e
3 changed files with 58 additions and 4 deletions
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18
rust/builder.go
View file

@ -158,7 +158,9 @@ func getTransformProperties(ctx ModuleContext, crateType string) transformProper
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 TransformRlibstoStaticlib(ctx android.ModuleContext, mainSrc android.Path,
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"))
}

15
rust/compiler.go
View file

@ -47,6 +47,7 @@ type compiler interface {
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 @@ type BaseCompilerProperties struct {
// 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 @@ func (compiler *baseCompiler) Disabled() bool {
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()")
}

29
rust/compiler_test.go
View file

@ -63,6 +63,35 @@ func TestCfgsToFlags(t *testing.T) {
}
}
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) {