[llvm-branch-commits] [llvm] [llvm][cmake] Turn runtime in PROJECTS warnings into FATAL_ERROR (PR #152302)

[David Spickett via llvm-branch-commits]

https://github.com/DavidSpickett created https://github.com/llvm/llvm-project/pull/152302

As promised by the current warning message:
CMake Warning at CMakeLists.txt:209 (message):
  Using LLVM_ENABLE_PROJECTS=openmp is deprecated now, and will become a
  fatal error in the LLVM 21 release.  Please use
  -DLLVM_ENABLE_RUNTIMES=openmp or see the instructions at
  https://openmp.llvm.org/ for building the runtimes.

I have changed this to:
CMake Warning at CMakeLists.txt:202 (message):
  Using LLVM_ENABLE_PROJECTS=openmp is no longer supported.  Please use
  -DLLVM_ENABLE_RUNTIMES=openmp or see the instructions at
  https://openmp.llvm.org/ for building the runtimes.

I removed the check for offload because offload never hits the warning, it errors earlier with:
CMake Error at CMakeLists.txt:143 (MESSAGE):
  offload isn't a known project:
  bolt;clang;clang-tools-extra;compiler-rt;cross-project-tests;libclc;lld;lldb;mlir;openmp;polly;flang;libc.
  Did you mean to enable it as a runtime in LLVM_ENABLE_RUNTIMES?

We could remove the FATAL_ERRORs entirely but I thought leaving them in 21.x and removing them on main made more sense.

So this change is specifically for 21.x.

>From afc78ab30f7ec81b7163fb4c3928cb08bd902766 Mon Sep 17 00:00:00 2001
From: David Spickett <david.spickett at linaro.org>
Date: Wed, 6 Aug 2025 12:35:05 +0000
Subject: [PATCH] [llvm][cmake] Turn runtime in PROJECTS warnings into
 FATAL_ERROR

As promised by the current warning message:
CMake Warning at CMakeLists.txt:209 (message):
  Using LLVM_ENABLE_PROJECTS=openmp is deprecated now, and will become a
  fatal error in the LLVM 21 release.  Please use
  -DLLVM_ENABLE_RUNTIMES=openmp or see the instructions at
  https://openmp.llvm.org/ for building the runtimes.

I have changed this to:
CMake Warning at CMakeLists.txt:202 (message):
  Using LLVM_ENABLE_PROJECTS=openmp is no longer supported.  Please use
  -DLLVM_ENABLE_RUNTIMES=openmp or see the instructions at
  https://openmp.llvm.org/ for building the runtimes.

I removed the check for offload because offload never hits the warning,
it errors earlier with:
CMake Error at CMakeLists.txt:143 (MESSAGE):
  offload isn't a known project:
  bolt;clang;clang-tools-extra;compiler-rt;cross-project-tests;libclc;lld;lldb;mlir;openmp;polly;flang;libc.
  Did you mean to enable it as a runtime in LLVM_ENABLE_RUNTIMES?

We could remove the FATAL_ERRORs entirely but I thought leaving
them in 21.x and removing them on main made more sense.

So this change is specifically for 21.x.
---
 llvm/CMakeLists.txt | 24 +++++++-----------------
 1 file changed, 7 insertions(+), 17 deletions(-)

diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
index 3f8201fa426fe..a16fb31cd320c 100644
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -180,29 +180,20 @@ if ("flang" IN_LIST LLVM_ENABLE_PROJECTS)
 endif()
 
 if ("libc" IN_LIST LLVM_ENABLE_PROJECTS)
-  message(WARNING "Using LLVM_ENABLE_PROJECTS=libc is deprecated.  Please use "
+  message(FATAL_ERROR "Using LLVM_ENABLE_PROJECTS=libc is no longer supported.  Please use "
     "-DLLVM_ENABLE_RUNTIMES=libc or see the instructions at "
     "https://libc.llvm.org/ for building the runtimes.")
 endif()
 
 if ("compiler-rt" IN_LIST LLVM_ENABLE_PROJECTS)
-  message(WARNING "Using LLVM_ENABLE_PROJECTS=compiler-rt is deprecated now, and will "
-    "become a fatal error in the LLVM 21 release.  Please use "
-    "-DLLVM_ENABLE_RUNTIMES=compiler-rt or see the instructions at "
+  message(FATAL_ERROR "Using LLVM_ENABLE_PROJECTS=compiler-rt is no longer supported. "
+    "Please use -DLLVM_ENABLE_RUNTIMES=compiler-rt or see the instructions at "
     "https://compiler-rt.llvm.org/ for building the runtimes.")
 endif()
 
-if ("offload" IN_LIST LLVM_ENABLE_PROJECTS)
-  message(WARNING "Using LLVM_ENABLE_PROJECTS=offload is deprecated now, and will "
-    "become a fatal error in the LLVM 21 release.  Please use "
-    "-DLLVM_ENABLE_RUNTIMES=offload or see the instructions at "
-    "https://openmp.llvm.org/ for building the runtimes.")
-endif()
-
 if ("openmp" IN_LIST LLVM_ENABLE_PROJECTS)
-  message(WARNING "Using LLVM_ENABLE_PROJECTS=openmp is deprecated now, and will "
-    "become a fatal error in the LLVM 21 release.  Please use "
-    "-DLLVM_ENABLE_RUNTIMES=openmp or see the instructions at "
+  message(FATAL_ERROR "Using LLVM_ENABLE_PROJECTS=openmp is no longer supported. "
+    "Please use -DLLVM_ENABLE_RUNTIMES=openmp or see the instructions at "
     "https://openmp.llvm.org/ for building the runtimes.")
 endif()
 
@@ -213,9 +204,8 @@ if ("flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES)
 endif ()
 
 if ("libclc" IN_LIST LLVM_ENABLE_PROJECTS)
-  message(WARNING "Using LLVM_ENABLE_PROJECTS=libclc is deprecated now, and will "
-    "become a fatal error in the LLVM 21 release.  Please use "
-    "-DLLVM_ENABLE_RUNTIMES=libclc or see the instructions at "
+  message(FATAL_ERROR "Using LLVM_ENABLE_PROJECTS=libclc is no longer supported. "
+    "Please use -DLLVM_ENABLE_RUNTIMES=libclc or see the instructions at "
     "https://libclc.llvm.org/ for building the runtimes.")
 endif()