[clang] [llvm] Define LLVM_ABI and CLANG_ABI for __EMSCRIPTEN__ builds (PR #131578)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Anutosh Bhat (anutosh491)

<details>
<summary>Changes</summary>

While building llvm (clang, lld) against emscripten we see this [error](https://github.com/emscripten-forge/recipes/actions/runs/13803029307/job/38608794602#step:9:1715)

```
 │ │ In file included from $SRC_DIR/llvm/lib/Frontend/OpenACC/ACC.cpp:9:
 │ │ $SRC_DIR/build/include/llvm/Frontend/OpenACC/ACC.h.inc:192:1: error: unknown type name 'LLVM_ABI'
 │ │   192 | LLVM_ABI Directive getOpenACCDirectiveKind(llvm::StringRef Str);
 │ │       | ^
 │ │ $SRC_DIR/build/include/llvm/Frontend/OpenACC/ACC.h.inc:192:19: error: expected ';' after top level declarator
 │ │   192 | LLVM_ABI Directive getOpenACCDirectiveKind(llvm::StringRef Str);
 │ │       |                   ^
 ```

Now this was happening because we weren't defining LLVM_ABI correctly when building against emscripten. If you see [llvm/Support/Compiler.h](https://github.com/llvm/llvm-project/blob/main/llvm/include/llvm/Support/Compiler.h#L206-L210), the condition only checked for the platform __WASM__ . Now Emscripten targets WebAssembly but doesn't imply the platform by default so the check isn't complete to define LLVM_ABI.

---
Full diff: https://github.com/llvm/llvm-project/pull/131578.diff


2 Files Affected:

- (modified) clang/include/clang/Support/Compiler.h (+1-1) 
- (modified) llvm/include/llvm/Support/Compiler.h (+1-1) 


``````````diff
diff --git a/clang/include/clang/Support/Compiler.h b/clang/include/clang/Support/Compiler.h
index 13582b899dc2a..5a74f8e3b6723 100644
--- a/clang/include/clang/Support/Compiler.h
+++ b/clang/include/clang/Support/Compiler.h
@@ -54,7 +54,7 @@
 #define CLANG_ABI LLVM_ATTRIBUTE_VISIBILITY_DEFAULT
 #define CLANG_TEMPLATE_ABI LLVM_ATTRIBUTE_VISIBILITY_DEFAULT
 #define CLANG_EXPORT_TEMPLATE
-#elif defined(__MACH__) || defined(__WASM__)
+#elif defined(__MACH__) || defined(__WASM__) || defined(__EMSCRIPTEN__)
 #define CLANG_ABI LLVM_ATTRIBUTE_VISIBILITY_DEFAULT
 #define CLANG_TEMPLATE_ABI
 #define CLANG_EXPORT_TEMPLATE
diff --git a/llvm/include/llvm/Support/Compiler.h b/llvm/include/llvm/Support/Compiler.h
index f9c57b89f1f03..dc8b5389069eb 100644
--- a/llvm/include/llvm/Support/Compiler.h
+++ b/llvm/include/llvm/Support/Compiler.h
@@ -203,7 +203,7 @@
 #define LLVM_TEMPLATE_ABI LLVM_ATTRIBUTE_VISIBILITY_DEFAULT
 #define LLVM_EXPORT_TEMPLATE
 #define LLVM_ABI_EXPORT LLVM_ATTRIBUTE_VISIBILITY_DEFAULT
-#elif defined(__MACH__) || defined(__WASM__)
+#elif defined(__MACH__) || defined(__WASM__) || defined(__EMSCRIPTEN__)
 #define LLVM_ABI LLVM_ATTRIBUTE_VISIBILITY_DEFAULT
 #define LLVM_TEMPLATE_ABI
 #define LLVM_EXPORT_TEMPLATE

``````````

</details>


https://github.com/llvm/llvm-project/pull/131578