From 5f367bbbd251b8cfb898f4d5711c9244888b1852 Mon Sep 17 00:00:00 2001
From: Urgau <urgau@numericable.fr>
Date: Fri, 23 Aug 2024 16:53:21 +0200
Subject: [PATCH] Make `download-ci-llvm = true` check if CI llvm is available

and make it the default for the compiler profile, as to prevent
unnecessarily checking out `src/llvm-project` with `"if-unchanged"`.
---
 config.example.toml                         | 5 ++++-
 src/bootstrap/defaults/config.compiler.toml | 3 ++-
 src/bootstrap/src/core/config/config.rs     | 3 ++-
 src/bootstrap/src/utils/change_tracker.rs   | 5 +++++
 4 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/config.example.toml b/config.example.toml
index e9433c9c9bd08..ed2db8218f00f 100644
--- a/config.example.toml
+++ b/config.example.toml
@@ -42,6 +42,9 @@
 # Unless you're developing for a target where Rust CI doesn't build a compiler
 # toolchain or changing LLVM locally, you probably want to leave this enabled.
 #
+# Set this to `true` to download if CI llvm available otherwise it builds
+# from `src/llvm-project`.
+#
 # Set this to `"if-unchanged"` to download only if the llvm-project has not
 # been modified. You can also use this if you are unsure whether you're on a
 # tier 1 target. All tier 1 targets are currently supported.
@@ -236,7 +239,7 @@
 # Instead of downloading the src/stage0 version of cargo-clippy specified,
 # use this cargo-clippy binary instead as the stage0 snapshot cargo-clippy.
 #
-# Note that this option should be used with the same toolchain as the `rustc` option above. 
+# Note that this option should be used with the same toolchain as the `rustc` option above.
 # Otherwise, clippy is likely to fail due to a toolchain conflict.
 #cargo-clippy = "/path/to/cargo-clippy"
 
diff --git a/src/bootstrap/defaults/config.compiler.toml b/src/bootstrap/defaults/config.compiler.toml
index 789586b58f706..147939d2047e8 100644
--- a/src/bootstrap/defaults/config.compiler.toml
+++ b/src/bootstrap/defaults/config.compiler.toml
@@ -27,4 +27,5 @@ assertions = false
 # Enable warnings during the LLVM compilation (when LLVM is changed, causing a compilation)
 enable-warnings = true
 # Will download LLVM from CI if available on your platform.
-download-ci-llvm = "if-unchanged"
+# If you intend to modify `src/llvm-project`, use `"if-unchanged"` or `false` instead.
+download-ci-llvm = true
diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
index 52c1c462788af..2edf6d385080b 100644
--- a/src/bootstrap/src/core/config/config.rs
+++ b/src/bootstrap/src/core/config/config.rs
@@ -2781,7 +2781,8 @@ impl Config {
                     );
                 }
 
-                b
+                // If download-ci-llvm=true we also want to check that CI llvm is available
+                b && llvm::is_ci_llvm_available(self, asserts)
             }
             Some(StringOrBool::String(s)) if s == "if-unchanged" => if_unchanged(),
             Some(StringOrBool::String(other)) => {
diff --git a/src/bootstrap/src/utils/change_tracker.rs b/src/bootstrap/src/utils/change_tracker.rs
index 80ab09881fe1c..99bcc6e0787ff 100644
--- a/src/bootstrap/src/utils/change_tracker.rs
+++ b/src/bootstrap/src/utils/change_tracker.rs
@@ -250,4 +250,9 @@ pub const CONFIG_CHANGE_HISTORY: &[ChangeInfo] = &[
         severity: ChangeSeverity::Info,
         summary: "New option `llvm.enzyme` to control whether the llvm based autodiff tool (Enzyme) is built.",
     },
+    ChangeInfo {
+        change_id: 129473,
+        severity: ChangeSeverity::Warning,
+        summary: "`download-ci-llvm = true` now checks if CI llvm is available and has become the default for the compiler profile",
+    },
 ];