[CIR] Change unreachable to diagnostic for ill-equipped clang #152614
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CLANG_ENABLE_CIR Add a new frontend diagnostic that informs users with ill-equipped clang binaries that they need to rebuild with -DCLANG_ENABLE_CIR=ON. This requires adding some plumbing for the new `cir-support` lit option. This improves the user experience as they may have a clang binary that wasn't built with MLIR/CIR support and using `-emit-cir` results in an unfriendly crash.
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@llvm/pr-subscribers-clang Author: Justin Stitt (JustinStitt) ChangesUsing a clang binary that wasn't built with MLIR/CIR support and using Add a new frontend diagnostic that informs users with ill-equipped clang binaries that they need to rebuild with Getting a worthwhile test involves adding some plumbing for a new As an aside, does Clang have any methods of hiding features in Full diff: https://github.com/llvm/llvm-project/pull/152614.diff 4 Files Affected:
diff --git a/clang/include/clang/Basic/DiagnosticFrontendKinds.td b/clang/include/clang/Basic/DiagnosticFrontendKinds.td
index 8a8db27490f06..89bca11540147 100644
--- a/clang/include/clang/Basic/DiagnosticFrontendKinds.td
+++ b/clang/include/clang/Basic/DiagnosticFrontendKinds.td
@@ -132,6 +132,8 @@ def err_fe_no_pch_in_dir : Error<
"no suitable precompiled header file found in directory '%0'">;
def err_fe_action_not_available : Error<
"action %0 not compiled in">;
+def err_fe_cir_not_built : Error<"clang IR support not available, rebuild "
+ "clang with -DCLANG_ENABLE_CIR=ON">;
def err_fe_invalid_multiple_actions : Error<
"'%0' action ignored; '%1' action specified previously">;
def err_fe_invalid_alignment : Error<
diff --git a/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp b/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
index 443eb4f1a29bf..67372a37c05f7 100644
--- a/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
+++ b/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
@@ -81,7 +81,8 @@ CreateFrontendBaseAction(CompilerInstance &CI) {
#if CLANG_ENABLE_CIR
return std::make_unique<cir::EmitCIRAction>();
#else
- llvm_unreachable("CIR suppport not built into clang");
+ CI.getDiagnostics().Report(diag::err_fe_cir_not_built);
+ return nullptr;
#endif
case EmitHTML: return std::make_unique<HTMLPrintAction>();
case EmitLLVM: {
diff --git a/clang/test/Frontend/cir-not-built.c b/clang/test/Frontend/cir-not-built.c
new file mode 100644
index 0000000000000..f9af2c4193b28
--- /dev/null
+++ b/clang/test/Frontend/cir-not-built.c
@@ -0,0 +1,12 @@
+// Test that using -emit-cir when clang is not built with CIR support gives a proper error message
+// instead of crashing.
+
+// This test should only run when CIR support is NOT enabled
+// REQUIRES: !cir-support
+
+// RUN: not %clang_cc1 -emit-cir %s 2>&1 | FileCheck %s
+// CHECK: error: clang IR support not available, rebuild clang with -DCLANG_ENABLE_CIR=ON
+
+int main(void) {
+ return 0;
+}
diff --git a/clang/test/lit.cfg.py b/clang/test/lit.cfg.py
index 1957bb1715eb6..4b2ecb0a6ca4c 100644
--- a/clang/test/lit.cfg.py
+++ b/clang/test/lit.cfg.py
@@ -224,6 +224,10 @@ def have_host_clang_repl_cuda():
)
)
+# ClangIR support
+if config.clang_enable_cir:
+ config.available_features.add("cir-support")
+
llvm_config.add_tool_substitutions(tools, tool_dirs)
config.substitutions.append(
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Aug 8, 2025
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Using a clang binary that wasn't built with MLIR/CIR support and using
-emit-cirresults in an unfriendly crash. We really shouldn't be abusing unreachables to inform users of mis-configurations.Add a new frontend diagnostic that informs users with ill-equipped clang binaries that they need to rebuild with
-DCLANG_ENABLE_CIR=ONto use-emit-cir. This matches how the frontend action diagnostics behave inExecuteCompilerInvocation.cppwitherr_fe_action_not_available.Getting a worthwhile test involves adding some plumbing for a new
cir-supportlit option.As an aside, does Clang have any methods of hiding features in
--helpwhen they are not compiled in? It might be a good idea to hide-emit-cirfrom the help text in this case.