[clang] [compiler-rt] [Clang][CodeGen] Report when an alias points to an incompatible target (PR #192397)

[Igor Kudrin via cfe-commits]

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@@ -804,6 +804,48 @@ void CodeGenModule::checkAliases() {
       continue;
     }
 
+    if (!IsIFunc) {
+      // Function declarations can only alias functions (including IFUNCs).
+      // Similarly, variable declarations can only alias variables.
+      if (isa<FunctionDecl>(D) != isa<llvm::Function, llvm::GlobalIFunc>(GV)) {
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igorkudrin wrote:

No, `GV` comes from `checkAliasedGlobal()`, which calls `getAliasedGlobal()` ➡️ `GlobalValue::getAliaseeObject()` ➡️ `findBaseObject()`, so we have the final alias target here.

The current condition directly reads as "one side is a function while the other is not", which is clear and fully corresponds to the intent. I could not find a similar phrase for `isa<FunctionDecl>(D) == isa<llvm::GlobalObject>(GV)`, so I chose the current variant for better readability. Not a strong preference, though.

https://github.com/llvm/llvm-project/pull/192397