Merging r312043:

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r312043 | rnk | 2017-08-29 14:44:21 -0700 (Tue, 29 Aug 2017) | 25 lines

[cmake] Stop putting the revision info in LLVM_VERSION_STRING

Summary:
This reduces the number of build actions after a no-op commit from
thousands to about six, which should be acceptable. If six actions is
still too many, developers can disable the LLVM_APPEND_VC_REV cmake
option.

llvm-config.h is a widely included header that should rarely change.
Before this patch, it would change after every re-configure. Very few
users of llvm-config.h need to know the precise version, and those that
do can migrate to incorporating LLVM_REVISION as provided by
llvm/Support/VCSRevision.h.

This should bring LLVM back to the behavior that it had before r306858
from June 30 2017. Most LLVM tools will now print a version string like
"6.0.0svn" instead of "6.0.0-git-c40c2a23de4".

Fixes PR34308

Reviewers: pcc, rafael, hans

Subscribers: mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D37272
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llvm-svn: 318344

llvm/CMakeLists.txt

@@ -208,10 +208,6 @@ include(VersionFromVCS)
 option(LLVM_APPEND_VC_REV
   "Embed the version control system revision id in LLVM" ON)
 
-if( LLVM_APPEND_VC_REV )
-  add_version_info_from_vcs(PACKAGE_VERSION)
-endif()
-
 set(PACKAGE_NAME LLVM)
 set(PACKAGE_STRING "${PACKAGE_NAME} ${PACKAGE_VERSION}")
 set(PACKAGE_BUGREPORT "http://llvm.org/bugs/")

llvm/docs/CMake.rst

@@ -248,9 +248,10 @@ LLVM-specific variables
 
 **LLVM_APPEND_VC_REV**:BOOL
   Embed version control revision info (svn revision number or Git revision id).
-  This is used among other things in the LLVM version string (stored in the
-  PACKAGE_VERSION macro). For this to work cmake must be invoked before the
-  build. Defaults to ON.
+  The version info is provided by the ``LLVM_REVISION`` macro in
+  ``llvm/include/llvm/Support/VCSRevision.h``. Developers using git who don't
+  need revision info can disable this option to avoid re-linking most binaries
+  after a branch switch. Defaults to ON.
 
 **LLVM_ENABLE_THREADS**:BOOL
   Build with threads support, if available. Defaults to ON.