From 2c9deaabf99dab9998f6ddbbe496d19ff7ce31f0 Mon Sep 17 00:00:00 2001
From: Fabio Valentini <decathorpe@gmail.com>
Date: Fri, 28 Aug 2020 21:56:45 +0200
Subject: [PATCH 2/2] Fix LTO with doctests

---
 .../src/cargo/core/compiler/context/mod.rs    |  3 +-
 .../cargo/src/cargo/core/compiler/mod.rs      | 59 +++++----------
 src/tools/cargo/src/cargo/core/profiles.rs    |  7 +-
 src/tools/cargo/tests/testsuite/lto.rs        | 71 ++++++++++++++++---
 4 files changed, 85 insertions(+), 55 deletions(-)

diff --git a/src/tools/cargo/src/cargo/core/compiler/context/mod.rs b/src/tools/cargo/src/cargo/core/compiler/context/mod.rs
index 52b954dd1..82831f423 100644
--- a/src/tools/cargo/src/cargo/core/compiler/context/mod.rs
+++ b/src/tools/cargo/src/cargo/core/compiler/context/mod.rs
@@ -210,7 +210,8 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
             // Collect information for `rustdoc --test`.
             if unit.mode.is_doc_test() {
                 let mut unstable_opts = false;
-                let args = compiler::extern_args(&self, unit, &mut unstable_opts)?;
+                let mut args = compiler::extern_args(&self, unit, &mut unstable_opts)?;
+                args.extend(compiler::lto_args(&self, unit));
                 self.compilation.to_doc_test.push(compilation::Doctest {
                     unit: unit.clone(),
                     args,
diff --git a/src/tools/cargo/src/cargo/core/compiler/mod.rs b/src/tools/cargo/src/cargo/core/compiler/mod.rs
index 9399c5042..47d2b9bb4 100644
--- a/src/tools/cargo/src/cargo/core/compiler/mod.rs
+++ b/src/tools/cargo/src/cargo/core/compiler/mod.rs
@@ -783,49 +783,9 @@ fn build_base_args(
         cmd.arg("-C").arg(format!("panic={}", panic));
     }
 
-    match cx.lto[unit] {
-        lto::Lto::Run(None) => {
-            cmd.arg("-C").arg("lto");
-        }
-        lto::Lto::Run(Some(s)) => {
-            cmd.arg("-C").arg(format!("lto={}", s));
-        }
-        lto::Lto::Off => {
-            cmd.arg("-C").arg("lto=off");
-        }
-        lto::Lto::ObjectAndBitcode => {} // this is rustc's default
-        lto::Lto::OnlyBitcode => {
-            // Note that this compiler flag, like the one below, is just an
-            // optimization in terms of build time. If we don't pass it then
-            // both object code and bitcode will show up. This is lagely just
-            // compat until the feature lands on stable and we can remove the
-            // conditional branch.
-            if cx
-                .bcx
-                .target_data
-                .info(CompileKind::Host)
-                .supports_embed_bitcode
-                .unwrap()
-            {
-                cmd.arg("-Clinker-plugin-lto");
-            }
-        }
-        lto::Lto::OnlyObject => {
-            if cx
-                .bcx
-                .target_data
-                .info(CompileKind::Host)
-                .supports_embed_bitcode
-                .unwrap()
-            {
-                cmd.arg("-Cembed-bitcode=no");
-            }
-        }
-    }
+    cmd.args(&lto_args(cx, unit));
 
     if let Some(n) = codegen_units {
-        // There are some restrictions with LTO and codegen-units, so we
-        // only add codegen units when LTO is not used.
         cmd.arg("-C").arg(&format!("codegen-units={}", n));
     }
 
@@ -952,6 +912,23 @@ fn build_base_args(
     Ok(())
 }
 
+fn lto_args(cx: &Context<'_, '_>, unit: &Unit) -> Vec<OsString> {
+    let mut result = Vec::new();
+    let mut push = |arg: &str| {
+        result.push(OsString::from("-C"));
+        result.push(OsString::from(arg));
+    };
+    match cx.lto[unit] {
+        lto::Lto::Run(None) => push("lto"),
+        lto::Lto::Run(Some(s)) => push(&format!("lto={}", s)),
+        lto::Lto::Off => push("lto=off"),
+        lto::Lto::ObjectAndBitcode => {} // this is rustc's default
+        lto::Lto::OnlyBitcode => push("linker-plugin-lto"),
+        lto::Lto::OnlyObject => push("embed-bitcode=no"),
+    }
+    result
+}
+
 fn build_deps_args(
     cmd: &mut ProcessBuilder,
     cx: &mut Context<'_, '_>,
diff --git a/src/tools/cargo/src/cargo/core/profiles.rs b/src/tools/cargo/src/cargo/core/profiles.rs
index 6a28bd261..ca0c2e417 100644
--- a/src/tools/cargo/src/cargo/core/profiles.rs
+++ b/src/tools/cargo/src/cargo/core/profiles.rs
@@ -302,7 +302,7 @@ impl Profiles {
             };
 
             match mode {
-                CompileMode::Test | CompileMode::Bench => {
+                CompileMode::Test | CompileMode::Bench | CompileMode::Doctest => {
                     if release {
                         (
                             InternedString::new("bench"),
@@ -315,10 +315,7 @@ impl Profiles {
                         )
                     }
                 }
-                CompileMode::Build
-                | CompileMode::Check { .. }
-                | CompileMode::Doctest
-                | CompileMode::RunCustomBuild => {
+                CompileMode::Build | CompileMode::Check { .. } | CompileMode::RunCustomBuild => {
                     // Note: `RunCustomBuild` doesn't normally use this code path.
                     // `build_unit_profiles` normally ensures that it selects the
                     // ancestor's profile. However, `cargo clean -p` can hit this
-- 
2.26.2