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

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-codegen

Author: Yeting Kuo (yetingk)

<details>
<summary>Changes</summary>

This fixes issue #<!-- -->63878 caused by creating an integer with zero bitwidth.

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


2 Files Affected:

- (modified) clang/lib/CodeGen/CGStmt.cpp (+4-1) 
- (added) clang/test/CodeGen/inline-asm-sizeless.c (+7) 


``````````diff
diff --git a/clang/lib/CodeGen/CGStmt.cpp b/clang/lib/CodeGen/CGStmt.cpp
index aa97f685ac7a9..92955e6cf4c96 100644
--- a/clang/lib/CodeGen/CGStmt.cpp
+++ b/clang/lib/CodeGen/CGStmt.cpp
@@ -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!");
       }
       ResultRegTypes.push_back(Ty);
       // If this output is tied to an input, and if the input is larger, then
diff --git a/clang/test/CodeGen/inline-asm-sizeless.c b/clang/test/CodeGen/inline-asm-sizeless.c
new file mode 100644
index 0000000000000..29c1fc5b0b8f7
--- /dev/null
+++ b/clang/test/CodeGen/inline-asm-sizeless.c
@@ -0,0 +1,7 @@
+// RUN: not %clang_cc1 -S %s -o /dev/null 2>&1 | FileCheck %s
+
+// CHECK: error: Output operand is sizeless!
+void foo(void) {
+    extern long bar[];
+    asm ("" : "=r"(bar));
+}

``````````

</details>


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