From 02c21060029cff4fdfd9eab3011a1fec6de2f9a0 Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov@redhat.com>
Date: Fri, 11 Mar 2022 10:55:48 +0100
Subject: [PATCH] [InstSimplify] Handle vector GEP when simplifying zero
 indices

If the base is a scalar and the index is a vector, we can't
simplify, as this is effectively a splat operation.
---
 llvm/lib/Analysis/InstructionSimplify.cpp     |  3 ++-
 .../Transforms/InstSimplify/opaque-ptr.ll     | 25 +++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 78850e4627c2..77d600ac5883 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4499,7 +4499,8 @@ static Value *SimplifyGEPInst(Type *SrcTy, Value *Ptr,
 
   // For opaque pointers an all-zero GEP is a no-op. For typed pointers,
   // it may be equivalent to a bitcast.
-  if (Ptr->getType()->isOpaquePointerTy() &&
+  if (Ptr->getType()->getScalarType()->isOpaquePointerTy() &&
+      Ptr->getType() == GEPTy &&
       all_of(Indices, [](const auto *V) { return match(V, m_Zero()); }))
     return Ptr;
 
diff --git a/llvm/test/Transforms/InstSimplify/opaque-ptr.ll b/llvm/test/Transforms/InstSimplify/opaque-ptr.ll
index 902b7c9392d5..48e75ac186ec 100644
--- a/llvm/test/Transforms/InstSimplify/opaque-ptr.ll
+++ b/llvm/test/Transforms/InstSimplify/opaque-ptr.ll
@@ -26,3 +26,28 @@ define ptr @gep_non_zero_indices2(ptr %p) {
   %p2 = getelementptr { i64, i64 }, ptr %p, i64 1, i32 0
   ret ptr %p2
 }
+
+define <2 x ptr> @scalar_base_vector_index(ptr %p) {
+; CHECK-LABEL: @scalar_base_vector_index(
+; CHECK-NEXT:    [[G:%.*]] = getelementptr { i64, i64 }, ptr [[P:%.*]], <2 x i64> zeroinitializer, i32 0
+; CHECK-NEXT:    ret <2 x ptr> [[G]]
+;
+  %g = getelementptr { i64, i64 }, ptr %p, <2 x i64> zeroinitializer, i32 0
+  ret <2 x ptr> %g
+}
+
+define <2 x ptr> @vector_base_vector_index(<2 x ptr> %p) {
+; CHECK-LABEL: @vector_base_vector_index(
+; CHECK-NEXT:    ret <2 x ptr> [[P:%.*]]
+;
+  %g = getelementptr { i64, i64 }, <2 x ptr> %p, <2 x i64> zeroinitializer, i32 0
+  ret <2 x ptr> %g
+}
+
+define <2 x ptr> @vector_base_scalar_index(<2 x ptr> %p) {
+; CHECK-LABEL: @vector_base_scalar_index(
+; CHECK-NEXT:    ret <2 x ptr> [[P:%.*]]
+;
+  %g = getelementptr { i64, i64 }, <2 x ptr> %p, i64 0, i32 0
+  ret <2 x ptr> %g
+}