[LoopVectorize] Fix crash on "Cannot dereference end iterator!"(PR56627)

Check hasOneUser before user_back().

Differential Revision: https://reviews.llvm.org/D136227

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 7983165..0a01b5f 100644 (file)
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -6561,10 +6561,9 @@ Optional<InstructionCost> LoopVectorizationCostModel::getReductionPatternCost(
       return None;
     RetI = RetI->user_back();
   }
-  if (match(RetI, m_Mul(m_Value(), m_Value())) &&
+
+  if (match(RetI, m_OneUse(m_Mul(m_Value(), m_Value()))) &&
       RetI->user_back()->getOpcode() == Instruction::Add) {
-    if (!RetI->hasOneUser())
-      return None;
     RetI = RetI->user_back();
   }
 

diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/pr56627.ll b/llvm/test/Transforms/LoopVectorize/AArch64/pr56627.ll
new file mode 100644 (file)
index 0000000..40fbd3e
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/pr56627.ll
@@ -0,0 +1,23 @@
+; RUN: opt < %s -S -passes=loop-vectorize | FileCheck %s
+
+; Check that we can vectorize this loop without crashing.
+
+target triple = "aarch64-none-linux-gnu"
+define float @quux() {
+; CHECK: @quux
+bb:
+  br label %bb1
+
+bb1:
+  %tmp = phi i64 [ %tmp3, %bb1 ], [ 0, %bb ]
+  %tmp2 = phi float [ %tmp5, %bb1 ], [ 0.000000e+00, %bb ]
+  %tmp3 = add nsw i64 %tmp, 1
+  %tmp5 = fadd float %tmp2, 3.000000e+00
+  %tmp6 = mul i32 0, 0
+  %tmp7 = icmp sgt i64 %tmp, 0
+  br i1 %tmp7, label %bb8, label %bb1
+
+bb8:
+  %tmp9 = phi float [ %tmp5, %bb1 ]
+  ret float %tmp9
+}
\ No newline at end of file