[llvm][ir]: fix llc crashes on function definitions with label parameters

[YLChenZ]

Closes #136144.

After the patch:

; label-crash.ll
define void @invalid_arg_type(i32 %0) {
1:
  call void @foo(label %1)
  ret void
}

declare void @foo(label)

lambda@ubuntu22:~/test$ llc -o out.s label-crash.ll 
Function argument cannot be of label type!
label %0
ptr @foo
llc: error: 'label-crash.ll': input module cannot be verified

[llvmbot]

@llvm/pr-subscribers-llvm-ir

Author: None (YLChenZ)

Changes

Closes #136144.

After the patch:

; label-crash.ll
define void @<!-- -->test(label %0) {
1:
    ret void
}

lambda@<!-- -->ubuntu22:~/test$ llc -o out.s label-crash.ll 
Function argument cannot be of label type!
label %0
llc: error: 'label-crash.ll': input module cannot be verified

---

Full diff: https://github.com/llvm/llvm-project/pull/136285.diff

2 Files Affected:

• (modified) llvm/lib/IR/Verifier.cpp (+2)
• (added) llvm/test/Verifier/invalid-label-param.ll (+7)

diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 35c4d60cf325e..274c60af52e76 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -2931,6 +2931,8 @@ void Verifier::visitFunction(const Function &F) {
           FT->getParamType(i));
     Check(Arg.getType()->isFirstClassType(),
           "Function arguments must have first-class types!", &Arg);
+    Check(!Arg.getType()->isLabelTy(),
+          "Function argument cannot be of label type!", &Arg);
     if (!IsIntrinsic) {
       Check(!Arg.getType()->isMetadataTy(),
             "Function takes metadata but isn't an intrinsic", &Arg, &F);
diff --git a/llvm/test/Verifier/invalid-label-param.ll b/llvm/test/Verifier/invalid-label-param.ll
new file mode 100644
index 0000000000000..6654c81a1754c
--- /dev/null
+++ b/llvm/test/Verifier/invalid-label-param.ll
@@ -0,0 +1,7 @@
+; RUN: not llvm-as < %s 2>&1 | FileCheck %s
+
+define void @invalid_arg_type(label %p) {
+; CHECK: Function argument cannot be of label type!
+  ret void
+}
+

[phoebewang]

We should allow it for asm, see https://github.com/llvm/llvm-project/blob/main/llvm/test/CodeGen/X86/asm-block-labels.ll

[nikic]

This is checking arguments on the function not calls.

Though really, we should not allow labels as inline asm operands either -- it looks like this is some leftover from an old implementation the predates both blockaddresses and callbr.

[phoebewang]

LGTM with one suggestion.

[phoebewang]

Add a test for call site, e.g.:

define void @test(i32 %0) {
1:
  call void @foo(label %1)
  ret void
}

declare void @foo(label)

[YLChenZ]

@phoebewang Done.