[clang] [clang][CodeGen] Don't crash on sizeless output. (PR #99849)

[Eli Friedman via cfe-commits]

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@@ -2751,7 +2751,10 @@ void CodeGenFunction::EmitAsmStmt(const AsmStmt &S) {
 
       if (RequiresCast) {
         unsigned Size = getContext().getTypeSize(QTy);
-        Ty = llvm::IntegerType::get(getLLVMContext(), Size);
+        if (Size)
+          Ty = llvm::IntegerType::get(getLLVMContext(), Size);
+        else
+          CGM.Error(S.getAsmLoc(), "Output operand is sizeless!");
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efriedma-quic wrote:

Can we use the SourceLocation of the specific operand in question, instead of using `S.getAsmLoc()`, which points at the beginning of the asm statement?

Diagnostics aren't capitalized, and don't end in punctuation.

Maybe say "size zero" instead of "sizeless".

https://github.com/llvm/llvm-project/pull/99849