From a35a93f09cc111a53d00efc567ad678583dd5ac7 Mon Sep 17 00:00:00 2001
From: Mingye Wang <arthur200126@gmail.com>
Date: Thu, 17 Sep 2020 17:39:26 +0800
Subject: Pass tune-cpu to LLVM

I think this is how it should work...
---
 compiler/rustc_codegen_llvm/src/attributes.rs | 15 +++++++++++++++
 compiler/rustc_codegen_llvm/src/context.rs    |  3 ++-
 compiler/rustc_codegen_llvm/src/lib.rs        |  3 +++
 compiler/rustc_codegen_llvm/src/llvm_util.rs  | 22 +++++++++++++++++-----
 4 files changed, 37 insertions(+), 6 deletions(-)

(limited to 'compiler/rustc_codegen_llvm/src')

diff --git a/compiler/rustc_codegen_llvm/src/attributes.rs b/compiler/rustc_codegen_llvm/src/attributes.rs
index 227a87ff819..434a42607d6 100644
--- a/compiler/rustc_codegen_llvm/src/attributes.rs
+++ b/compiler/rustc_codegen_llvm/src/attributes.rs
@@ -194,6 +194,18 @@ pub fn apply_target_cpu_attr(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) {
     );
 }
 
+pub fn apply_tune_cpu_attr(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) {
+    if let Some(tune) = llvm_util::tune_cpu(cx.tcx.sess) {
+        let tune_cpu = SmallCStr::new(tune);
+        llvm::AddFunctionAttrStringValue(
+            llfn,
+            llvm::AttributePlace::Function,
+            const_cstr!("tune-cpu"),
+            tune_cpu.as_c_str(),
+        );
+    }
+}
+
 /// Sets the `NonLazyBind` LLVM attribute on a given function,
 /// assuming the codegen options allow skipping the PLT.
 pub fn non_lazy_bind(sess: &Session, llfn: &'ll Value) {
@@ -300,6 +312,9 @@ pub fn from_fn_attrs(cx: &CodegenCx<'ll, 'tcx>, llfn: &'ll Value, instance: ty::
     // Without this, ThinLTO won't inline Rust functions into Clang generated
     // functions (because Clang annotates functions this way too).
     apply_target_cpu_attr(cx, llfn);
+    // tune-cpu is only conveyed through the attribute for our purpose.
+    // The target doesn't care; the subtarget reads our attribute.
+    apply_tune_cpu_attr(cx, llfn);
 
     let features = llvm_target_features(cx.tcx.sess)
         .map(|s| s.to_string())
diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
index 1c51a9df5d8..6e6b2cacc03 100644
--- a/compiler/rustc_codegen_llvm/src/context.rs
+++ b/compiler/rustc_codegen_llvm/src/context.rs
@@ -417,7 +417,8 @@ impl MiscMethods<'tcx> for CodegenCx<'ll, 'tcx> {
     }
 
     fn apply_target_cpu_attr(&self, llfn: &'ll Value) {
-        attributes::apply_target_cpu_attr(self, llfn)
+        attributes::apply_target_cpu_attr(self, llfn);
+        attributes::apply_tune_cpu_attr(self, llfn);
     }
 
     fn create_used_variable(&self) {
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
index 2e2abe9fb30..28e49e823c0 100644
--- a/compiler/rustc_codegen_llvm/src/lib.rs
+++ b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -116,6 +116,9 @@ impl ExtraBackendMethods for LlvmCodegenBackend {
     fn target_cpu<'b>(&self, sess: &'b Session) -> &'b str {
         llvm_util::target_cpu(sess)
     }
+    fn tune_cpu<'b>(&self, sess: &'b Session) -> Option<&'b str> {
+        llvm_util::tune_cpu(sess)
+    }
 }
 
 impl WriteBackendMethods for LlvmCodegenBackend {
diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs
index f0b50459837..7fe30fc8ac0 100644
--- a/compiler/rustc_codegen_llvm/src/llvm_util.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs
@@ -351,11 +351,7 @@ pub(crate) fn print(req: PrintRequest, sess: &Session) {
     }
 }
 
-pub fn target_cpu(sess: &Session) -> &str {
-    let name = match sess.opts.cg.target_cpu {
-        Some(ref s) => &**s,
-        None => &*sess.target.target.options.cpu,
-    };
+fn handle_native(name: &str) -> &str {
     if name != "native" {
         return name;
     }
@@ -366,3 +362,19 @@ pub fn target_cpu(sess: &Session) -> &str {
         str::from_utf8(slice::from_raw_parts(ptr as *const u8, len)).unwrap()
     }
 }
+
+pub fn target_cpu(sess: &Session) -> &str {
+    let name = match sess.opts.cg.target_cpu {
+        Some(ref s) => &**s,
+        None => &*sess.target.target.options.cpu,
+    };
+
+    handle_native(name)
+}
+
+pub fn tune_cpu(sess: &Session) -> Option<&str> {
+    match sess.opts.debugging_opts.tune_cpu {
+        Some(ref s) => Some(handle_native(&**s)),
+        None => None,
+    }
+}
-- 
cgit 1.4.1-3-g733a5