diff --git a/source/opt/merge_return_pass.cpp b/source/opt/merge_return_pass.cpp
index d0434f2..a13540c 100644
--- a/source/opt/merge_return_pass.cpp
+++ b/source/opt/merge_return_pass.cpp
@@ -206,7 +206,11 @@
     RecordReturned(block);
     RecordReturnValue(block);
   }
+
   BasicBlock* target_block = context()->get_instr_block(target);
+  if (target_block->GetLoopMergeInst()) {
+    cfg()->SplitLoopHeader(target_block);
+  }
   UpdatePhiNodes(block, target_block);
 
   Instruction* return_inst = block->terminator();
@@ -241,8 +245,22 @@
   if (inst.result_id() != 0) {
     std::vector<Instruction*> users_to_update;
     context()->get_def_use_mgr()->ForEachUser(
-        &inst, [&users_to_update, &dom_tree, inst_bb, this](Instruction* user) {
-          BasicBlock* user_bb = context()->get_instr_block(user);
+        &inst,
+        [&users_to_update, &dom_tree, &inst, inst_bb, this](Instruction* user) {
+          BasicBlock* user_bb = nullptr;
+          if (user->opcode() != SpvOpPhi) {
+            user_bb = context()->get_instr_block(user);
+          } else {
+            // For OpPhi, the use should be considered to be in the predecessor.
+            for (uint32_t i = 0; i < user->NumInOperands(); i += 2) {
+              if (user->GetSingleWordInOperand(i) == inst.result_id()) {
+                uint32_t user_bb_id = user->GetSingleWordInOperand(i + 1);
+                user_bb = context()->get_instr_block(user_bb_id);
+                break;
+              }
+            }
+          }
+
           // If |user_bb| is nullptr, then |user| is not in the function.  It is
           // something like an OpName or decoration, which should not be
           // replaced with the result of the OpPhi.
@@ -362,6 +380,9 @@
       return false;
     }
   }
+  if (merge_block->GetLoopMergeInst()) {
+    cfg()->SplitLoopHeader(merge_block);
+  }
 
   // Leave the phi instructions behind.
   auto iter = block->begin();
diff --git a/test/opt/pass_merge_return_test.cpp b/test/opt/pass_merge_return_test.cpp
index 7f2c058..e49fec9 100644
--- a/test/opt/pass_merge_return_test.cpp
+++ b/test/opt/pass_merge_return_test.cpp
@@ -1145,6 +1145,115 @@
   EXPECT_TRUE(messages.empty());
 }
 
+TEST_F(MergeReturnPassTest, StructuredControlFlowDontChangeEntryPhi) {
+  const std::string before =
+      R"(
+; CHECK: OpFunction %void
+; CHECK: OpLabel
+; CHECK: OpLabel
+; CHECK: [[pre_header:%\w+]] = OpLabel
+; CHECK: [[header:%\w+]] = OpLabel
+; CHECK-NEXT: OpPhi %bool {{%\w+}} [[pre_header]] [[iv:%\w+]] [[continue:%\w+]]
+; CHECK-NEXT: OpLoopMerge [[merge:%\w+]] [[continue]]
+; CHECK: [[continue]] = OpLabel
+; CHECK-NEXT: [[iv]] = Op
+; CHECK: [[merge]] = OpLabel
+               OpCapability Shader
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint Vertex %1 "main"
+       %void = OpTypeVoid
+       %bool = OpTypeBool
+          %4 = OpTypeFunction %void
+          %1 = OpFunction %void None %4
+          %5 = OpLabel
+          %6 = OpUndef %bool
+               OpBranch %7
+          %7 = OpLabel
+          %8 = OpPhi %bool %6 %5 %9 %10
+               OpLoopMerge %11 %10 None
+               OpBranch %12
+         %12 = OpLabel
+         %13 = OpUndef %bool
+               OpSelectionMerge %10 DontFlatten
+               OpBranchConditional %13 %10 %14
+         %14 = OpLabel
+               OpReturn
+         %10 = OpLabel
+          %9 = OpUndef %bool
+               OpBranchConditional %13 %7 %11
+         %11 = OpLabel
+               OpReturn
+               OpFunctionEnd
+
+)";
+
+  SetAssembleOptions(SPV_TEXT_TO_BINARY_OPTION_PRESERVE_NUMERIC_IDS);
+  SinglePassRunAndMatch<MergeReturnPass>(before, false);
+}
+
+TEST_F(MergeReturnPassTest, StructuredControlFlowPartialReplacePhi) {
+  const std::string before =
+      R"(
+; CHECK: OpFunction %void
+; CHECK: OpLabel
+; CHECK: OpLabel
+; CHECK: [[pre_header:%\w+]] = OpLabel
+; CHECK: [[header:%\w+]] = OpLabel
+; CHECK-NEXT: OpPhi
+; CHECK-NEXT: OpLoopMerge [[merge:%\w+]]
+; CHECK: OpLabel
+; CHECK: [[old_ret_block:%\w+]] = OpLabel
+; CHECK: [[bb:%\w+]] = OpLabel
+; CHECK-NEXT: [[val:%\w+]] = OpUndef %bool
+; CHECK: [[merge]] = OpLabel
+; CHECK-NEXT: [[phi1:%\w+]] = OpPhi %bool [[val]] [[bb]] {{%\w+}} [[old_ret_block]]
+; CHECK: OpBranchConditional {{%\w+}} {{%\w+}} [[bb2:%\w+]]
+; CHECK: [[bb2]] = OpLabel
+; CHECK: OpBranch [[header2:%\w+]]
+; CHECK: [[header2]] = OpLabel
+; CHECK-NEXT: [[phi2:%\w+]] = OpPhi %bool [[phi1]] [[continue2:%\w+]] [[phi1]] [[bb2]]
+; CHECK-NEXT: OpLoopMerge {{%\w+}} [[continue2]]
+; CHECK: [[continue2]] = OpLabel
+; CHECK-NEXT: OpBranch [[header2]]
+               OpCapability Shader
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint Vertex %1 "main"
+       %void = OpTypeVoid
+       %bool = OpTypeBool
+          %4 = OpTypeFunction %void
+          %1 = OpFunction %void None %4
+          %5 = OpLabel
+          %6 = OpUndef %bool
+               OpBranch %7
+          %7 = OpLabel
+          %8 = OpPhi %bool %6 %5 %9 %10
+               OpLoopMerge %11 %10 None
+               OpBranch %12
+         %12 = OpLabel
+         %13 = OpUndef %bool
+               OpSelectionMerge %10 DontFlatten
+               OpBranchConditional %13 %10 %14
+         %14 = OpLabel
+               OpReturn
+         %10 = OpLabel
+          %9 = OpUndef %bool
+               OpBranchConditional %13 %7 %11
+         %11 = OpLabel
+          %phi = OpPhi %bool %9 %10 %9 %cont
+               OpLoopMerge %ret %cont None
+               OpBranch %bb
+         %bb = OpLabel
+               OpBranchConditional %13 %ret %cont
+         %cont = OpLabel
+               OpBranch %11
+         %ret = OpLabel
+               OpReturn
+               OpFunctionEnd
+)";
+
+  SetAssembleOptions(SPV_TEXT_TO_BINARY_OPTION_PRESERVE_NUMERIC_IDS);
+  SinglePassRunAndMatch<MergeReturnPass>(before, false);
+}
 }  // namespace
 }  // namespace opt
 }  // namespace spvtools