Fix clone_constant_impl to correctly deal with null pointers

Summary:
This patch resolves llvm-c-test's following error

```
LLVM ERROR: LLVMGetValueKind returned incorrect type
```

which arises when the input bitcode contains a null pointer.

Reviewers: jdoerfert, CodaFi, deadalnix

Reviewed By: jdoerfert

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68928

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/tools/llvm-c-test/echo.cpp b/llvm/tools/llvm-c-test/echo.cpp
index 4d10a4bbfc0..8abbfb3fb0c 100644
--- a/llvm/tools/llvm-c-test/echo.cpp
+++ b/llvm/tools/llvm-c-test/echo.cpp
@@ -326,6 +326,13 @@ static LLVMValueRef clone_constant_impl(LLVMValueRef Cst, LLVMModuleRef M) {
                                     EltCount, LLVMIsPackedStruct(Ty));
   }
 
+  // Try ConstantPointerNull
+  if (LLVMIsAConstantPointerNull(Cst)) {
+    check_value_kind(Cst, LLVMConstantPointerNullValueKind);
+    LLVMTypeRef Ty = TypeCloner(M).Clone(Cst);
+    return LLVMConstNull(Ty);
+  }
+
   // Try undef
   if (LLVMIsUndef(Cst)) {
     check_value_kind(Cst, LLVMUndefValueValueKind);