[clang] clang: Set the exception model module flag for IR inputs (PR #228372)

[via cfe-commits]

llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-webassembly

Author: Matt Arsenault (arsenm)

<details>
<summary>Changes</summary>

Previously the -exception-model cc1 flag did nothing for IR inputs. Record the
module flag in the IR input path too, next to the existing triple override. A
 model contradicting one the input module already records is rejected matching
err_data_layout_mismatch and the conflict llc reports for the same pair of
inputs.

This is to keep the wasm-eh.ll test passing when the TargetOptions field for
ExecptionModel is removed. I'm not sure if this behavior really needs to be
preserved given the bitcode producers should now materialize the flag in the
IR.

Co-authored-by: Claude Opus 5 <noreply@<!-- -->anthropic.com>

---
Full diff: https://github.com/llvm/llvm-project/pull/228372.diff


4 Files Affected:

- (modified) clang/include/clang/Basic/DiagnosticFrontendKinds.td (+3) 
- (modified) clang/lib/CodeGen/CodeGenAction.cpp (+18) 
- (added) clang/test/CodeGen/WebAssembly/wasm-exception-model-flag-ir-input-mismatch.ll (+20) 
- (modified) clang/test/CodeGen/WebAssembly/wasm-exception-model-flag-parse-ir-input.ll (+6-2) 


``````````diff
diff --git a/clang/include/clang/Basic/DiagnosticFrontendKinds.td b/clang/include/clang/Basic/DiagnosticFrontendKinds.td
index 840bade06643031..c8ade96ae3d5043 100644
--- a/clang/include/clang/Basic/DiagnosticFrontendKinds.td
+++ b/clang/include/clang/Basic/DiagnosticFrontendKinds.td
@@ -505,6 +505,9 @@ def warn_hlsl_failed_to_embed_source
 
 def err_data_layout_mismatch : Error<"backend data layout '%0' does not match "
                                      "expected target description '%1'">;
+def err_fe_exception_model_mismatch
+    : Error<"'-exception-model=%0' does not match the module's exception "
+            "model '%1'">;
 def err_failed_to_open_for_embedding
     : Error<"could not open '%0' for embedding">;
 def err_unsupported_cxx_abi_feature
diff --git a/clang/lib/CodeGen/CodeGenAction.cpp b/clang/lib/CodeGen/CodeGenAction.cpp
index 7b2d39069702ad0..de677a385d832be 100644
--- a/clang/lib/CodeGen/CodeGenAction.cpp
+++ b/clang/lib/CodeGen/CodeGenAction.cpp
@@ -575,6 +575,24 @@ void CodeGenAction::ExecuteAction() {
     TheModule->setTargetTriple(Triple(TargetOpts.Triple));
   }
 
+  llvm::ExceptionHandling ExceptionModel =
+      CodeGenOptions::toExceptionHandling(CodeGenOpts.getExceptionHandling());
+  if (ExceptionModel != llvm::ExceptionHandling::Default) {
+    StringRef ModelName = llvm::getExceptionModelName(ExceptionModel);
+    if (auto *Existing = cast_or_null<llvm::MDString>(
+            TheModule->getModuleFlag("exception-model"))) {
+      if (Existing->getString() != ModelName) {
+        Diagnostics.Report(diag::err_fe_exception_model_mismatch)
+            << ModelName << Existing->getString();
+        return;
+      }
+    } else {
+      TheModule->addModuleFlag(
+          llvm::Module::Error, "exception-model",
+          llvm::MDString::get(TheModule->getContext(), ModelName));
+    }
+  }
+
   EmbedObject(TheModule.get(), CodeGenOpts, CI.getVirtualFileSystem(),
               Diagnostics);
   EmbedBitcode(TheModule.get(), CodeGenOpts, *MainFile);
diff --git a/clang/test/CodeGen/WebAssembly/wasm-exception-model-flag-ir-input-mismatch.ll b/clang/test/CodeGen/WebAssembly/wasm-exception-model-flag-ir-input-mismatch.ll
new file mode 100644
index 000000000000000..c8aef1d31b0aac1
--- /dev/null
+++ b/clang/test/CodeGen/WebAssembly/wasm-exception-model-flag-ir-input-mismatch.ll
@@ -0,0 +1,20 @@
+; REQUIRES: webassembly-registered-target
+
+; An -exception-model= matching the input module's flag is accepted.
+; RUN: %clang_cc1 -triple wasm32 -o - -emit-llvm -exception-model=wasm %s | FileCheck %s
+
+; A contradicting one is rejected.
+; RUN: not %clang_cc1 -triple wasm32 -o - -emit-llvm -exception-model=none %s 2>&1 | FileCheck -check-prefix=NONE %s
+; RUN: not %clang_cc1 -triple wasm32 -o - -emit-llvm -exception-model=emscripten %s 2>&1 | FileCheck -check-prefix=EM %s
+
+; CHECK: !{i32 1, !"exception-model", !"wasm"}
+
+; NONE: error: '-exception-model=none' does not match the module's exception model 'wasm'
+; EM: error: '-exception-model=emscripten' does not match the module's exception model 'wasm'
+
+define void @test() {
+  ret void
+}
+
+!llvm.module.flags = !{!0}
+!0 = !{i32 1, !"exception-model", !"wasm"}
diff --git a/clang/test/CodeGen/WebAssembly/wasm-exception-model-flag-parse-ir-input.ll b/clang/test/CodeGen/WebAssembly/wasm-exception-model-flag-parse-ir-input.ll
index 1410de231660a88..b3ac28b47226727 100644
--- a/clang/test/CodeGen/WebAssembly/wasm-exception-model-flag-parse-ir-input.ll
+++ b/clang/test/CodeGen/WebAssembly/wasm-exception-model-flag-parse-ir-input.ll
@@ -1,8 +1,8 @@
 ; REQUIRES: webassembly-registered-target
 
 ; Check all the options parse
-; RUN: %clang_cc1 -triple wasm32 -o - -emit-llvm -exception-model=none %s | FileCheck %s
-; RUN: %clang_cc1 -triple wasm32 -o - -emit-llvm -exception-model=wasm %s | FileCheck %s
+; RUN: %clang_cc1 -triple wasm32 -o - -emit-llvm -exception-model=none %s | FileCheck -check-prefixes=CHECK,NONE %s
+; RUN: %clang_cc1 -triple wasm32 -o - -emit-llvm -exception-model=wasm %s | FileCheck -check-prefixes=CHECK,WASM %s
 
 ; RUN: not %clang_cc1 -triple wasm32 -o - -emit-llvm -exception-model=invalid %s 2>&1 | FileCheck -check-prefix=ERR %s
 ; RUN: not %clang_cc1 -triple wasm32 -o - -emit-llvm -exception-model=dwarf %s 2>&1 | FileCheck -check-prefix=ERR-BE %s
@@ -10,6 +10,10 @@
 
 ; CHECK-LABEL: define void @test(
 
+; The model is recorded on the module, as it is for source input.
+; NONE: !{i32 1, !"exception-model", !"none"}
+; WASM: !{i32 1, !"exception-model", !"wasm"}
+
 ; ERR: error: invalid value 'invalid' in '-exception-model=invalid'
 ; ERR-BE: fatal error: error in backend: -exception-model should be either 'none', 'wasm', or 'emscripten'
 define void @test() {

``````````

</details>


https://github.com/llvm/llvm-project/pull/228372