Implement basic support for PGO in rustbuild for rustc

src/bootstrap/compile.rs

@@ -501,6 +501,20 @@ impl Step for Rustc {
         let mut cargo = builder.cargo(compiler, Mode::Rustc, SourceType::InTree, target, "build");
         rustc_cargo(builder, &mut cargo, target);
 
+        if let Some(path) = &builder.config.rust_profile_generate {
+            if compiler.stage == 1 {
+                cargo.rustflag(&format!("-Cprofile-generate={}", path));
+                // Apparently necessary to avoid overflowing the counters during
+                // a Cargo build profile
+                cargo.rustflag("-Cllvm-args=-vp-counters-per-site=4");
+            }
+        }
+        if let Some(path) = &builder.config.rust_profile_use {
+            if compiler.stage == 1 {
+                cargo.rustflag(&format!("-Cprofile-use={}", path));
+            }
+        }
+
         builder.info(&format!(
             "Building stage{} compiler artifacts ({} -> {})",
             compiler.stage, &compiler.host, target
@@ -752,7 +766,7 @@ fn copy_codegen_backends_to_sysroot(
     // Here we're looking for the output dylib of the `CodegenBackend` step and
     // we're copying that into the `codegen-backends` folder.
     let dst = builder.sysroot_codegen_backends(target_compiler);
-    t!(fs::create_dir_all(&dst));
+    t!(fs::create_dir_all(&dst), dst);
 
     if builder.config.dry_run {
         return;

src/bootstrap/config.rs

@@ -133,6 +133,8 @@ pub struct Config {
     pub rust_thin_lto_import_instr_limit: Option<u32>,
     pub rust_remap_debuginfo: bool,
     pub rust_new_symbol_mangling: bool,
+    pub rust_profile_use: Option<String>,
+    pub rust_profile_generate: Option<String>,
 
     pub build: TargetSelection,
     pub hosts: Vec<TargetSelection>,
@@ -494,6 +496,8 @@ struct Rust {
     llvm_libunwind: Option<String>,
     control_flow_guard: Option<bool>,
     new_symbol_mangling: Option<bool>,
+    profile_generate: Option<String>,
+    profile_use: Option<String>,
 }
 
 /// TOML representation of how each build target is configured.
@@ -871,6 +875,11 @@ impl Config {
 
             config.rust_codegen_units = rust.codegen_units.map(threads_from_config);
             config.rust_codegen_units_std = rust.codegen_units_std.map(threads_from_config);
+            config.rust_profile_use = flags.rust_profile_use.or(rust.profile_use);
+            config.rust_profile_generate = flags.rust_profile_generate.or(rust.profile_generate);
+        } else {
+            config.rust_profile_use = flags.rust_profile_use;
+            config.rust_profile_generate = flags.rust_profile_generate;
         }
 
         if let Some(t) = toml.target {

src/bootstrap/flags.rs

@@ -68,6 +68,9 @@ pub struct Flags {
     pub deny_warnings: Option<bool>,
 
     pub llvm_skip_rebuild: Option<bool>,
+
+    pub rust_profile_use: Option<String>,
+    pub rust_profile_generate: Option<String>,
 }
 
 pub enum Subcommand {
@@ -219,6 +222,8 @@ To learn more about a subcommand, run `./x.py <subcommand> -h`",
              VALUE overrides the skip-rebuild option in config.toml.",
             "VALUE",
         );
+        opts.optopt("", "rust-profile-generate", "rustc error format", "FORMAT");
+        opts.optopt("", "rust-profile-use", "rustc error format", "FORMAT");
 
         // We can't use getopt to parse the options until we have completed specifying which
         // options are valid, but under the current implementation, some options are conditional on
@@ -674,6 +679,8 @@ Arguments:
             color: matches
                 .opt_get_default("color", Color::Auto)
                 .expect("`color` should be `always`, `never`, or `auto`"),
+            rust_profile_use: matches.opt_str("rust-profile-use"),
+            rust_profile_generate: matches.opt_str("rust-profile-generate"),
         }
     }
 }

src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile

@@ -85,6 +85,7 @@ ENV CC=clang CXX=clang++
 COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
+
 ENV HOSTS=x86_64-unknown-linux-gnu
 
 ENV RUST_CONFIGURE_ARGS \
@@ -98,9 +99,8 @@ ENV RUST_CONFIGURE_ARGS \
       --set llvm.thin-lto=true \
       --set llvm.ninja=false \
       --set rust.jemalloc
-ENV SCRIPT python2.7 ../x.py dist --host $HOSTS --target $HOSTS \
-        --include-default-paths \
-        src/tools/build-manifest
+COPY host-x86_64/dist-x86_64-linux/pgo.sh /tmp/
+ENV SCRIPT /tmp/pgo.sh
 ENV CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang
 
 # This is the only builder which will create source tarballs

src/ci/docker/host-x86_64/dist-x86_64-linux/pgo.sh

@@ -0,0 +1,50 @@
+#!/bin/bash
+
+set -euxo pipefail
+
+rm -rf /tmp/rustc-pgo
+
+python2.7 ../x.py build --stage 2 library/std --rust-profile-generate=/tmp/rustc-pgo
+
+./build/x86_64-unknown-linux-gnu/stage2/bin/rustc --edition=2018 \
+    --crate-type=lib ../library/core/src/lib.rs
+
+PERF=e095f5021bf01cf3800f50b3a9f14a9683eb3e4e
+
+curl -o /tmp/externs.rs \
+https://raw.githubusercontent.com/rust-lang/rustc-perf/$PERF/collector/benchmarks/externs/src/lib.rs
+./build/x86_64-unknown-linux-gnu/stage2/bin/rustc --edition=2018 --crate-type=lib /tmp/externs.rs
+
+curl -o /tmp/ctfe.rs \
+https://raw.githubusercontent.com/rust-lang/rustc-perf/$PERF/collector/benchmarks/ctfe-stress-4/src/lib.rs
+./build/x86_64-unknown-linux-gnu/stage2/bin/rustc --edition=2018 --crate-type=lib /tmp/ctfe.rs
+
+cp -pri ../src/tools/cargo /tmp/cargo
+
+RUSTC=./build/x86_64-unknown-linux-gnu/stage2/bin/rustc CARGO_INCREMENTAL=1 \
+    ./build/x86_64-unknown-linux-gnu/stage0/bin/cargo check \
+    --manifest-path /tmp/cargo/Cargo.toml
+echo 'pub fn barbarbar() {}' >> /tmp/cargo/src/cargo/lib.rs
+RUSTC=./build/x86_64-unknown-linux-gnu/stage2/bin/rustc CARGO_INCREMENTAL=1 \
+    ./build/x86_64-unknown-linux-gnu/stage0/bin/cargo check \
+    --manifest-path /tmp/cargo/Cargo.toml
+touch /tmp/cargo/src/cargo/lib.rs
+RUSTC=./build/x86_64-unknown-linux-gnu/stage2/bin/rustc CARGO_INCREMENTAL=1 \
+    ./build/x86_64-unknown-linux-gnu/stage0/bin/cargo check \
+    --manifest-path /tmp/cargo/Cargo.toml
+RUSTC=./build/x86_64-unknown-linux-gnu/stage2/bin/rustc CARGO_INCREMENTAL=1 \
+    ./build/x86_64-unknown-linux-gnu/stage0/bin/cargo check \
+    --manifest-path /tmp/cargo/Cargo.toml
+RUSTC=./build/x86_64-unknown-linux-gnu/stage2/bin/rustc \
+    ./build/x86_64-unknown-linux-gnu/stage0/bin/cargo build --release \
+    --manifest-path /tmp/cargo/Cargo.toml
+./build/x86_64-unknown-linux-gnu/llvm/bin/llvm-profdata \
+    merge -o /tmp/rustc-pgo.profdata /tmp/rustc-pgo
+
+cp /tmp/rustc-pgo.profdata ./build/dist/rustc-pgo.profdata
+
+# This produces the actual final set of artifacts
+python2.7 ../x.py dist --rust-profile-use=/tmp/rustc-pgo.profdata \
+    --host $HOSTS --target $HOSTS \
+    --include-default-paths \
+    src/tools/build-manifest

src/ci/docker/scripts/pgo.rs

@@ -0,0 +1 @@
+fn main() {}