Use std uplifting more often

Author: Kobzol

src/bootstrap/src/core/build_steps/compile.rs

@@ -99,28 +99,12 @@ impl Std {
         deps
     }
 
-    /// Returns true if the standard library will be uplifted from stage 1 for the given
-    /// `build_compiler` (which determines the stdlib stage) and `target`.
+    /// Returns true if the standard library should be uplifted from stage 1.
     ///
-    /// Uplifting is enabled if we're building a stage2+ libstd, full bootstrap is
-    /// disabled and we have a stage1 libstd already compiled for the given target.
-    pub fn should_be_uplifted_from_stage_1(
-        builder: &Builder<'_>,
-        stage: u32,
-        target: TargetSelection,
-    ) -> bool {
-        stage > 1
-            && !builder.config.full_bootstrap
-            // This estimates if a stage1 libstd exists for the given target. If we're not
-            // cross-compiling, it should definitely exist by the time we're building a stage2
-            // libstd.
-            // Or if we are cross-compiling, and we are building a cross-compiled rustc, then that
-            // rustc needs to link to a cross-compiled libstd, so again we should have a stage1
-            // libstd for the given target prepared.
-            // Even if we guess wrong in the cross-compiled case, the worst that should happen is
-            // that we build a fresh stage1 libstd below, and then we immediately uplift it, so we
-            // don't pay the libstd build cost twice.
-            && (target == builder.host_target || builder.config.hosts.contains(&target))
+    /// Uplifting is enabled if we're building a stage2+ libstd and full bootstrap is
+    /// disabled.
+    pub fn should_be_uplifted_from_stage_1(builder: &Builder<'_>, stage: u32) -> bool {
+        stage > 1 && !builder.config.full_bootstrap
     }
 }
 
@@ -228,7 +212,7 @@ impl Step for Std {
         // Stage of the stdlib that we're building
         let stage = build_compiler.stage;
 
-        if Self::should_be_uplifted_from_stage_1(builder, build_compiler.stage, target) {
+        if Self::should_be_uplifted_from_stage_1(builder, build_compiler.stage) {
             let build_compiler_for_std_to_uplift = builder.compiler(1, builder.host_target);
             let stage_1_stamp = builder.std(build_compiler_for_std_to_uplift, target);
 

src/bootstrap/src/core/build_steps/dist.rs

@@ -115,7 +115,7 @@ impl Step for JsonDocs {
 
     fn make_run(run: RunConfig<'_>) {
         run.builder.ensure(JsonDocs {
-            build_compiler: run.builder.compiler_for_std(run.builder.top_stage, run.target),
+            build_compiler: run.builder.compiler_for_std(run.builder.top_stage),
             target: run.target,
         });
     }
@@ -769,7 +769,7 @@ pub struct Std {
 
 impl Std {
     pub fn new(builder: &Builder<'_>, target: TargetSelection) -> Self {
-        Std { build_compiler: builder.compiler_for_std(builder.top_stage, target), target }
+        Std { build_compiler: builder.compiler_for_std(builder.top_stage), target }
     }
 }
 

src/bootstrap/src/core/build_steps/doc.rs

@@ -616,9 +616,7 @@ impl Step for Std {
             return;
         }
         run.builder.ensure(Std {
-            build_compiler: run
-                .builder
-                .compiler_for_std(run.builder.top_stage, run.builder.host_target),
+            build_compiler: run.builder.compiler_for_std(run.builder.top_stage),
             target: run.target,
             format: if run.builder.config.cmd.json() {
                 DocumentationFormat::Json

src/bootstrap/src/core/builder/mod.rs

@@ -1373,10 +1373,11 @@ impl<'a> Builder<'a> {
     /// we need:
     /// - stage 2 libstd for target2 (uplifted from stage 1, where it was built by target1 rustc)
     /// - stage 2 rustc for target2
+    ///
     /// However, without this optimization, we would also build stage 2 rustc for **target1**,
     /// which is completely wasteful.
-    pub fn compiler_for_std(&self, stage: u32, target: TargetSelection) -> Compiler {
-        if compile::Std::should_be_uplifted_from_stage_1(self, stage, target) {
+    pub fn compiler_for_std(&self, stage: u32) -> Compiler {
+        if compile::Std::should_be_uplifted_from_stage_1(self, stage) {
             self.compiler(1, self.host_target)
         } else {
             self.compiler(stage, self.host_target)

src/bootstrap/src/core/builder/tests.rs

@@ -1066,6 +1066,7 @@ mod snapshot {
         [build] rustc 1 <host> -> rustc 2 <target1>
         [build] rustc 2 <host> -> std 2 <host>
         [build] rustc 2 <host> -> std 2 <target1>
+        [build] rustc 1 <host> -> std 1 <target2>
         [build] rustc 2 <host> -> std 2 <target2>
         ");
     }
@@ -1295,16 +1296,15 @@ mod snapshot {
         [dist] docs <target1>
         [doc] rustc 1 <host> -> std 1 <host> crates=[]
         [dist] rustc 1 <host> -> json-docs 2 <host>
-        [build] rustdoc 2 <host>
-        [doc] rustc 2 <host> -> std 2 <target1> crates=[]
-        [dist] rustc 2 <host> -> json-docs 3 <target1>
+        [doc] rustc 1 <host> -> std 1 <target1> crates=[]
+        [dist] rustc 1 <host> -> json-docs 2 <target1>
         [dist] mingw <host>
         [dist] mingw <target1>
+        [build] rustdoc 2 <host>
         [build] rustc 0 <host> -> GenerateCopyright 1 <host>
         [dist] rustc <host>
         [dist] rustc 1 <host> -> std 1 <host>
-        [build] rustc 2 <host> -> std 2 <target1>
-        [dist] rustc 2 <host> -> std 2 <target1>
+        [dist] rustc 1 <host> -> std 1 <target1>
         [dist] rustc 1 <host> -> rustc-dev 2 <host>
         [dist] src <>
         [dist] reproducible-artifacts <host>
@@ -1495,13 +1495,10 @@ mod snapshot {
         [doc] rustc 1 <host> -> releases 2 <target1>
         [build] rustc 0 <host> -> RustInstaller 1 <host>
         [dist] docs <target1>
-        [build] rustc 1 <host> -> rustc 2 <host>
-        [build] rustdoc 2 <host>
-        [doc] rustc 2 <host> -> std 2 <target1> crates=[]
-        [dist] rustc 2 <host> -> json-docs 3 <target1>
+        [doc] rustc 1 <host> -> std 1 <target1> crates=[]
+        [dist] rustc 1 <host> -> json-docs 2 <target1>
         [dist] mingw <target1>
-        [build] rustc 2 <host> -> std 2 <target1>
-        [dist] rustc 2 <host> -> std 2 <target1>
+        [dist] rustc 1 <host> -> std 1 <target1>
         ");
     }