pcboot/rust-opt-size-flag.diff at master · rprichard/pcboot · GitHub

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commit 71e9f85ab1b84b9a3a70fd106998758872cb9a0d
Author: Ryan Prichard <ryan.prichard@gmail.com>
Date:   Wed Oct 15 14:12:40 2014 -0700

    Add an --opt-size rustc flag and an opt_size function attribute.

diff --git a/src/librustc/driver/config.rs b/src/librustc/driver/config.rs
index f5423b2..4f48088 100644
--- a/src/librustc/driver/config.rs
+++ b/src/librustc/driver/config.rs
@@ -70,6 +70,7 @@ pub struct Options {

     pub gc: bool,
     pub optimize: OptLevel,
+    pub opt_size: bool,
     pub debuginfo: DebugInfoLevel,
     pub lint_opts: Vec<(String, lint::Level)>,
     pub describe_lints: bool,
@@ -110,6 +111,7 @@ pub fn basic_options() -> Options {
         crate_types: Vec::new(),
         gc: false,
         optimize: No,
+        opt_size: false,
         debuginfo: NoDebugInfo,
         lint_opts: Vec::new(),
         describe_lints: false,
@@ -595,6 +597,7 @@ pub fn optgroups() -> Vec<getopts::OptGroup> {
         optflag("O", "", "Equivalent to --opt-level=2"),
         optopt("o", "", "Write output to <filename>", "FILENAME"),
         optopt("", "opt-level", "Optimize with possible levels 0-3", "LEVEL"),
+        optflag("", "opt-size", "Optimize for small code"),
         optopt( "",  "out-dir", "Write output to compiler-chosen filename in <dir>", "DIR"),
         optflag("", "parse-only", "Parse only; do not compile, assemble, or link"),
         optopt("", "explain", "Provide a detailed explanation of an error message", "OPT"),
@@ -739,6 +742,7 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
             No
         }
     };
+    let opt_size = matches.opt_present("opt-size");
     let gc = debugging_opts & GC != 0;
     let debuginfo = if matches.opt_present("g") {
         if matches.opt_present("debuginfo") {
@@ -822,6 +826,7 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
         crate_types: crate_types,
         gc: gc,
         optimize: opt_level,
+        opt_size: opt_size,
         debuginfo: debuginfo,
         lint_opts: lint_opts,
         describe_lints: describe_lints,
diff --git a/src/librustc/lint/builtin.rs b/src/librustc/lint/builtin.rs
index 76234c4..9e9e358 100644
--- a/src/librustc/lint/builtin.rs
+++ b/src/librustc/lint/builtin.rs
@@ -572,6 +572,7 @@ impl LintPass for UnusedAttributes {
             "no_mangle",
             "no_split_stack",
             "no_stack_check",
+            "opt_size",
             "packed",
             "static_assert",
             "thread_local",
diff --git a/src/librustc/middle/trans/base.rs b/src/librustc/middle/trans/base.rs
index ebc46bb..f663393 100644
--- a/src/librustc/middle/trans/base.rs
+++ b/src/librustc/middle/trans/base.rs
@@ -207,6 +207,9 @@ pub fn decl_fn(ccx: &CrateContext, name: &str, cc: llvm::CallConv,
     if ccx.is_split_stack_supported() && !ccx.sess().opts.cg.no_stack_check {
         set_split_stack(llfn);
     }
+    if ccx.sess().opts.opt_size {
+        set_optimize_for_size(llfn);
+    }

     llfn
 }
@@ -426,7 +429,6 @@ pub fn get_tydesc(ccx: &CrateContext, t: ty::t) -> Rc<tydesc_info> {
     inf
 }

-#[allow(dead_code)] // useful
 pub fn set_optimize_for_size(f: ValueRef) {
     llvm::SetFunctionAttribute(f, llvm::OptimizeForSizeAttribute)
 }
@@ -474,6 +476,7 @@ pub fn set_llvm_fn_attrs(ccx: &CrateContext, attrs: &[ast::Attribute], llfn: Val
                                                llvm::FunctionIndex as c_uint,
                                                llvm::ColdAttribute as uint64_t)
             },
+            "opt_size" => set_optimize_for_size(llfn),
             _ => used = false,
         }
         if used {