[llvm] [Verifier] Reject va_start in non-variadic function (PR #88809)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-ir

@llvm/pr-subscribers-backend-aarch64

Author: Jon Chesterfield (JonChesterfield)

<details>
<summary>Changes</summary>

A va_start intrinsic lowers to something derived from the variadic parameter to the function. If there is no such parameter, it can't lower meaningfully. Clang sema rejects the same with `error: 'va_start' used in function with fixed args`.

Moves the existing lint warning into a verifier error. Updates the one lit test that had a va_start in a non-variadic function.

---
Full diff: https://github.com/llvm/llvm-project/pull/88809.diff


5 Files Affected:

- (modified) llvm/lib/Analysis/Lint.cpp (+1-4) 
- (modified) llvm/lib/IR/Verifier.cpp (+5) 
- (modified) llvm/test/CodeGen/AArch64/GlobalISel/vastart.ll (+1-1) 
- (modified) llvm/test/Other/lint.ll (-7) 
- (added) llvm/test/Verifier/variadic.ll (+8) 


``````````diff
diff --git a/llvm/lib/Analysis/Lint.cpp b/llvm/lib/Analysis/Lint.cpp
index 0694c2995dfcce..1ab856ac8830a9 100644
--- a/llvm/lib/Analysis/Lint.cpp
+++ b/llvm/lib/Analysis/Lint.cpp
@@ -350,10 +350,7 @@ void Lint::visitCallBase(CallBase &I) {
     }
 
     case Intrinsic::vastart:
-      Check(I.getParent()->getParent()->isVarArg(),
-            "Undefined behavior: va_start called in a non-varargs function",
-            &I);
-
+      // vastart in non-varargs function is rejected by the verifier
       visitMemoryReference(I, MemoryLocation::getForArgument(&I, 0, TLI),
                            std::nullopt, nullptr, MemRef::Read | MemRef::Write);
       break;
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 33f358440a312d..8720bfc2093b5b 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -5769,6 +5769,11 @@ void Verifier::visitIntrinsicCall(Intrinsic::ID ID, CallBase &Call) {
 
     break;
   }
+  case Intrinsic::vastart: {
+    Check(Call.getFunction()->isVarArg(),
+          "va_start called in a non-varargs function");
+    break;
+  }
   case Intrinsic::vector_reduce_and:
   case Intrinsic::vector_reduce_or:
   case Intrinsic::vector_reduce_xor:
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/vastart.ll b/llvm/test/CodeGen/AArch64/GlobalISel/vastart.ll
index bd576d0f70e9c1..8c6e01d934c2d8 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/vastart.ll
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/vastart.ll
@@ -3,7 +3,7 @@
 
 
 declare void @llvm.va_start(ptr)
-define void @test_va_start(ptr %list) {
+define void @test_va_start(ptr %list, ...) {
 ; CHECK-LABEL: name: test_va_start
 ; CHECK: [[LIST:%[0-9]+]]:_(p0) = COPY $x0
 ; CHECK-IOS: G_VASTART [[LIST]](p0) :: (store (s64) into %ir.list, align 1)
diff --git a/llvm/test/Other/lint.ll b/llvm/test/Other/lint.ll
index 6b31b31a78c98a..6fd2d40cd2f298 100644
--- a/llvm/test/Other/lint.ll
+++ b/llvm/test/Other/lint.ll
@@ -124,13 +124,6 @@ define void @0() nounwind {
   ret void
 }
 
-; CHECK: va_start called in a non-varargs function
-declare void @llvm.va_start(ptr)
-define void @not_vararg(ptr %p) nounwind {
-  call void @llvm.va_start(ptr %p)
-  ret void
-}
-
 ; CHECK: Undefined behavior: Branch to non-blockaddress
 define void @use_indbr() {
   indirectbr ptr @foo, [label %block]
diff --git a/llvm/test/Verifier/variadic.ll b/llvm/test/Verifier/variadic.ll
new file mode 100644
index 00000000000000..55e4a4da0a9203
--- /dev/null
+++ b/llvm/test/Verifier/variadic.ll
@@ -0,0 +1,8 @@
+; RUN: not opt -S -passes=verify 2>&1 < %s | FileCheck %s
+
+; CHECK: va_start called in a non-varargs function
+declare void @llvm.va_start(ptr)
+define void @not_vararg(ptr %p) nounwind {
+  call void @llvm.va_start(ptr %p)
+  ret void
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/88809