From 7d56483207b8102855bd0c3cd8f6e5412165736c Mon Sep 17 00:00:00 2001
From: Nikita Popov <nikita.ppv@gmail.com>
Date: Thu, 9 Sep 2021 21:55:28 +0200
Subject: [PATCH] [IR] Handle constant expressions in
 containsUndefinedElement()

If the constant is a constant expression, then getAggregateElement()
will return null. Guard against this before calling HasFn().

(cherry picked from commit af382b93831ae6a58bce8bc075458cfd056e3976)
---
 lib/IR/Constants.cpp                                | 8 +++++---
 test/Transforms/InstSimplify/ConstProp/vecreduce.ll | 9 +++++++++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/lib/IR/Constants.cpp b/lib/IR/Constants.cpp
index 6c75085a667..1e72cb4d3a6 100644
--- a/lib/IR/Constants.cpp
+++ b/lib/IR/Constants.cpp
@@ -315,9 +315,11 @@ containsUndefinedElement(const Constant *C,
       return false;
 
     for (unsigned i = 0, e = cast<FixedVectorType>(VTy)->getNumElements();
-         i != e; ++i)
-      if (HasFn(C->getAggregateElement(i)))
-        return true;
+         i != e; ++i) {
+      if (Constant *Elem = C->getAggregateElement(i))
+        if (HasFn(Elem))
+          return true;
+    }
   }
 
   return false;
diff --git a/test/Transforms/InstSimplify/ConstProp/vecreduce.ll b/test/Transforms/InstSimplify/ConstProp/vecreduce.ll
index e27180b1a89..b407c908cf2 100644
--- a/test/Transforms/InstSimplify/ConstProp/vecreduce.ll
+++ b/test/Transforms/InstSimplify/ConstProp/vecreduce.ll
@@ -87,6 +87,15 @@ define i32 @add_poison1() {
   ret i32 %x
 }
 
+define i32 @add_constexpr() {
+; CHECK-LABEL: @add_constexpr(
+; CHECK-NEXT:    [[X:%.*]] = call i32 @llvm.vector.reduce.add.v8i32(<8 x i32> bitcast (<4 x i64> <i64 0, i64 1, i64 2, i64 3> to <8 x i32>))
+; CHECK-NEXT:    ret i32 [[X]]
+;
+  %x = call i32 @llvm.vector.reduce.add.v8i32(<8 x i32> bitcast (<4 x i64> <i64 0, i64 1, i64 2, i64 3> to <8 x i32>))
+  ret i32 %x
+}
+
 define i32 @mul_0() {
 ; CHECK-LABEL: @mul_0(
 ; CHECK-NEXT:    ret i32 0