llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-codegen
Author: Kerry McLaughlin (kmclaughlin-arm)
<details>
<summary>Changes</summary>
When functions are passed as arguments to a lambda, it's possible for
the mangled names of these functions to be the same despite the prototypes
being different. For example:
```
int non_streaming_fn(int);
int streaming_fn(int) __arm_streaming;
auto lambda_fn = [](const auto &f) { return f(); };
return lambda_fn(non_streaming_fn) + lambda_fn(streaming_fn);
```
Only one function will be generated for the lambda above and the __arm_streaming
attribute from streaming_fn will be incorrectly applied to the non_streaming_fn
call.
With this change, an error will be emitted when a duplicate mangled name is
found
but the function prototypes do not match.
---
Full diff: https://github.com/llvm/llvm-project/pull/107581.diff
2 Files Affected:
- (modified) clang/lib/CodeGen/CodeGenModule.cpp (+26-9)
- (added) clang/test/CodeGenCXX/aarch64-sme-lambda-attributes.cpp (+28)
``````````diff
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp
b/clang/lib/CodeGen/CodeGenModule.cpp
index df4c13c9ad97aa..b07090e3de6dfd 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -4638,8 +4638,8 @@ llvm::Constant *CodeGenModule::GetOrCreateLLVMFunction(
// Lookup the entry, lazily creating it if necessary.
llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
if (Entry) {
+ const FunctionDecl *FD = cast_or_null<FunctionDecl>(D);
if (WeakRefReferences.erase(Entry)) {
- const FunctionDecl *FD = cast_or_null<FunctionDecl>(D);
if (FD && !FD->hasAttr<WeakAttr>())
Entry->setLinkage(llvm::Function::ExternalLinkage);
}
@@ -4652,18 +4652,35 @@ llvm::Constant *CodeGenModule::GetOrCreateLLVMFunction(
// If there are two attempts to define the same mangled name, issue an
// error.
- if (IsForDefinition && !Entry->isDeclaration()) {
- GlobalDecl OtherGD;
- // Check that GD is not yet in DiagnosedConflictingDefinitions is
required
- // to make sure that we issue an error only once.
- if (lookupRepresentativeDecl(MangledName, OtherGD) &&
- (GD.getCanonicalDecl().getDecl() !=
- OtherGD.getCanonicalDecl().getDecl()) &&
- DiagnosedConflictingDefinitions.insert(GD).second) {
+ GlobalDecl OtherGD;
+ // Check that GD is not yet in DiagnosedConflictingDefinitions is required
+ // to make sure that we issue an error only once.
+ if (GD && lookupRepresentativeDecl(MangledName, OtherGD) &&
+ (GD.getCanonicalDecl().getDecl() !=
+ OtherGD.getCanonicalDecl().getDecl()) &&
+ DiagnosedConflictingDefinitions.insert(GD).second) {
+ if (IsForDefinition && !Entry->isDeclaration()) {
getDiags().Report(D->getLocation(), diag::err_duplicate_mangled_name)
<< MangledName;
getDiags().Report(OtherGD.getDecl()->getLocation(),
diag::note_previous_definition);
+ } else {
+ // For lambdas, it's possible to create the same mangled name from
+ // different function prototypes. For example, two FPTs may have
+ // identical types but incompatible function attributes which we should
+ // not allow.
+ auto *MD = dyn_cast<CXXMethodDecl>(D);
+ if (MD && MD->getParent()->isLambda()) {
+ const FunctionDecl *OtherFD =
+ cast_or_null<FunctionDecl>(OtherGD.getDecl());
+ if (FD && FD->hasPrototype() && OtherFD && OtherFD->hasPrototype()) {
+ if (FD->getType()->getAs<FunctionProtoType>() !=
+ OtherFD->getType()->getAs<FunctionProtoType>())
+ getDiags().Report(D->getLocation(),
+ diag::err_duplicate_mangled_name)
+ << MangledName;
+ }
+ }
}
}
diff --git a/clang/test/CodeGenCXX/aarch64-sme-lambda-attributes.cpp
b/clang/test/CodeGenCXX/aarch64-sme-lambda-attributes.cpp
new file mode 100644
index 00000000000000..bce3e657001679
--- /dev/null
+++ b/clang/test/CodeGenCXX/aarch64-sme-lambda-attributes.cpp
@@ -0,0 +1,28 @@
+// REQUIRES: aarch64-registered-target
+
+// RUN: %clang_cc1 -triple aarch64 -target-feature +sme -target-feature +sme2
-emit-llvm -o - %s -verify -DTEST1
+// RUN: %clang_cc1 -triple aarch64 -target-feature +sme -target-feature +sme2
-emit-llvm -o - %s -verify -DTEST2
+
+int normal_fn(int);
+int streaming_fn(int) __arm_streaming;
+int streaming_compatible_fn(int) __arm_streaming_compatible;
+
+#ifdef TEST1
+
+// expected-error@+2 {{definition with same mangled name
'_ZZ32function_params_normal_streamingvENK3$_0clIFiiEEEDaRT_' as another
definition}}
+int function_params_normal_streaming() {
+ auto a = [](auto &fn) { return fn(42); };
+ return a(normal_fn) + a(streaming_fn);
+}
+
+#endif
+
+#ifdef TEST2
+
+// expected-error@+2 {{definition with same mangled name
'_ZZ36function_params_streaming_compatiblevENK3$_0clIFiiEEEDaRT_' as another
definition}}
+int function_params_streaming_compatible() {
+ auto a = [](auto &fn) { return fn(42); };
+ return a(streaming_fn) + a(streaming_compatible_fn);
+}
+
+#endif
``````````
</details>
https://github.com/llvm/llvm-project/pull/107581
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