rustbuild: LLVM is not partially rebuilt anymore #68715

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1. petrochenkov

   added

   A-LLVMArea: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.

   T-bootstrapRelevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap)Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap)

   on Jan 31, 2020
2. cuviper commented on Jan 31, 2020

   

   cuviper

   on Jan 31, 2020

   Member

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   I think it's because the git hash is set in LLVM_VERSION_SUFFIX here:
   

   rust/src/bootstrap/native.rs

   Lines 240 to 253 in cd1ef39

   	if let Some(ref suffix) = builder.config.llvm_version_suffix {
   	// Allow version-suffix="" to not define a version suffix at all.
   	if !suffix.is_empty() {
   	cfg.define("LLVM_VERSION_SUFFIX", suffix);
   	}
   	} else {
   	let mut default_suffix =
   	format!("-rust-{}-{}", channel::CFG_RELEASE_NUM, builder.config.channel,);
   	if let Some(sha) = llvm_info.sha_short() {
   	default_suffix.push_str("-");
   	default_suffix.push_str(sha);
   	}
   	cfg.define("LLVM_VERSION_SUFFIX", default_suffix);
   	}

   This propagates to PACKAGE_VERSION in llvm/Config/config.h, which affects the entire build.
3. cuviper commented on Feb 1, 2020

   

   cuviper

   on Feb 1, 2020

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   There's a cmake variable LLVM_APPEND_VC_REV that would probably behave better for this.
4. tmiasko commented on Feb 23, 2020

   

   tmiasko

   on Feb 23, 2020

   Contributor

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   The LLVM_VERSION_SUFFIX is indeed responsible for complete rebuilds.
   The intent behind PR that introduced it was to disambiguate between versions of
   LLVM library that are incompatible yet previously could share the same name.

   Unfortunately LLVM_APPEND_VC_REV doesn't help, since it is about stashing
   version control revision information somewhere inside the library, rather than
   changing the library name itself.

   Removing commit SHA from default version suffix should be enough to address
   the original issue while resolving this one.
5. JohnTitor

   added a commit that references this issue on Mar 1, 2020

   Rollup merge of rust-lang#69397 - tmiasko:llvm-version-suffix, r=nagisa

   ...

   This issue will close once commit 1e25878 is merged into the 'main' branch.

   1e25878
6. bors

   closed this as completedin 1e25878on Mar 1, 2020