Auto merge of #70882 - tmiasko:llvm-version-suffix, r=Mark-Simulacrum

Make LLVM version suffix independent of rustc version on dev channel

Remove rustc version from LLVM version suffix on dev channel,
avoiding the need for full rebuilds when switching between
branches with different LLVM submodule & rustc version.

Note: To avoid full rebuild, on subsequent LLVM submodule update, copy the
current value of `LLVM_VERSION_SUFFIX` from `build/*/llvm/build/CMakeCache.txt`,
to `version-suffix` in `config.toml`.

1 files changed, 7 insertions, 3 deletions

diff --git a/src/bootstrap/native.rs b/src/bootstrap/native.rs
index d4d66abd520..1e380a20629 100644
--- a/src/bootstrap/native.rs
+++ b/src/bootstrap/native.rs
@@ -235,10 +235,14 @@ impl Step for Llvm {
             if !suffix.is_empty() {
                 cfg.define("LLVM_VERSION_SUFFIX", suffix);
             }
+        } else if builder.config.channel == "dev" {
+            // Changes to a version suffix require a complete rebuild of the LLVM.
+            // To avoid rebuilds during a time of version bump, don't include rustc
+            // release number on the dev channel.
+            cfg.define("LLVM_VERSION_SUFFIX", "-rust-dev");
         } else {
-            let default_suffix =
-                format!("-rust-{}-{}", channel::CFG_RELEASE_NUM, builder.config.channel);
-            cfg.define("LLVM_VERSION_SUFFIX", default_suffix);
+            let suffix = format!("-rust-{}-{}", channel::CFG_RELEASE_NUM, builder.config.channel);
+            cfg.define("LLVM_VERSION_SUFFIX", suffix);
         }
 
         if let Some(ref linker) = builder.config.llvm_use_linker {