Transform to combine consecutive access chains

* Combines OpAccessChain, OpInBoundsAccessChain, OpPtrAccessChain and
OpInBoundsPtrAccessChain
* New folding rule to fold add with 0 for integers
 * Converts to a bitcast if the result type does not match the operand
 type
V

12 files changed, 1299 insertions, 4 deletions

diff --git a/Android.mk b/Android.mk
index ffd3064b..a1cf282b 100644
--- a/Android.mk
+++ b/Android.mk
@@ -68,6 +68,7 @@ SPVTOOLS_OPT_SRC_FILES := \
 		source/opt/cfg.cpp \
 		source/opt/cfg_cleanup_pass.cpp \
 		source/opt/ccp_pass.cpp \
+		source/opt/combine_access_chains.cpp \
 		source/opt/common_uniform_elim_pass.cpp \
 		source/opt/compact_ids_pass.cpp \
 		source/opt/composite.cpp \
diff --git a/include/spirv-tools/optimizer.hpp b/include/spirv-tools/optimizer.hpp
index 6e193bdb..2849e28c 100644
--- a/include/spirv-tools/optimizer.hpp
+++ b/include/spirv-tools/optimizer.hpp
@@ -636,6 +636,11 @@ Optimizer::PassToken CreateVectorDCEPass();
 // a load of the specific elements.
 Optimizer::PassToken CreateReduceLoadSizePass();
 
+// Create a pass to combine chained access chains.
+// This pass looks for access chains fed by other access chains and combines
+// them into a single instruction where possible.
+Optimizer::PassToken CreateCombineAccessChainsPass();
+
 }  // namespace spvtools
 
 #endif  // SPIRV_TOOLS_OPTIMIZER_HPP_
diff --git a/source/opt/CMakeLists.txt b/source/opt/CMakeLists.txt
index 484dd5f3..d9fc8c9f 100644
--- a/source/opt/CMakeLists.txt
+++ b/source/opt/CMakeLists.txt
@@ -19,6 +19,7 @@ add_library(SPIRV-Tools-opt
   ccp_pass.h
   cfg_cleanup_pass.h
   cfg.h
+  combine_access_chains.h
   common_uniform_elim_pass.h
   compact_ids_pass.h
   composite.h
@@ -106,6 +107,7 @@ add_library(SPIRV-Tools-opt
   ccp_pass.cpp
   cfg_cleanup_pass.cpp
   cfg.cpp
+  combine_access_chains.cpp
   common_uniform_elim_pass.cpp
   compact_ids_pass.cpp
   composite.cpp
diff --git a/source/opt/combine_access_chains.cpp b/source/opt/combine_access_chains.cpp
new file mode 100644
index 00000000..ccefb258
--- /dev/null
+++ b/source/opt/combine_access_chains.cpp
@@ -0,0 +1,288 @@
+// Copyright (c) 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "combine_access_chains.h"
+
+#include "constants.h"
+#include "ir_builder.h"
+#include "ir_context.h"
+
+namespace spvtools {
+namespace opt {
+
+Pass::Status CombineAccessChains::Process() {
+  bool modified = false;
+
+  for (auto& function : *get_module()) {
+    modified |= ProcessFunction(function);
+  }
+
+  return (modified ? Status::SuccessWithChange : Status::SuccessWithoutChange);
+}
+
+bool CombineAccessChains::ProcessFunction(Function& function) {
+  bool modified = false;
+
+  cfg()->ForEachBlockInReversePostOrder(
+      function.entry().get(), [&modified, this](BasicBlock* block) {
+        block->ForEachInst([&modified, this](Instruction* inst) {
+          switch (inst->opcode()) {
+            case SpvOpAccessChain:
+            case SpvOpInBoundsAccessChain:
+            case SpvOpPtrAccessChain:
+            case SpvOpInBoundsPtrAccessChain:
+              modified |= CombineAccessChain(inst);
+              break;
+            default:
+              break;
+          }
+        });
+      });
+
+  return modified;
+}
+
+uint32_t CombineAccessChains::GetConstantValue(
+    const analysis::Constant* constant_inst) {
+  if (constant_inst->type()->AsInteger()->width() <= 32) {
+    if (constant_inst->type()->AsInteger()->IsSigned()) {
+      return static_cast<uint32_t>(constant_inst->GetS32());
+    } else {
+      return constant_inst->GetU32();
+    }
+  } else {
+    assert(false);
+    return 0u;
+  }
+}
+
+uint32_t CombineAccessChains::GetArrayStride(const Instruction* inst) {
+  uint32_t array_stride = 0;
+  context()->get_decoration_mgr()->WhileEachDecoration(
+      inst->type_id(), SpvDecorationArrayStride,
+      [&array_stride](const Instruction& decoration) {
+        assert(decoration.opcode() != SpvOpDecorateId);
+        if (decoration.opcode() == SpvOpDecorate) {
+          array_stride = decoration.GetSingleWordInOperand(1);
+        } else {
+          array_stride = decoration.GetSingleWordInOperand(2);
+        }
+        return false;
+      });
+  return array_stride;
+}
+
+const analysis::Type* CombineAccessChains::GetIndexedType(Instruction* inst) {
+  analysis::DefUseManager* def_use_mgr = context()->get_def_use_mgr();
+  analysis::TypeManager* type_mgr = context()->get_type_mgr();
+
+  Instruction* base_ptr = def_use_mgr->GetDef(inst->GetSingleWordInOperand(0));
+  const analysis::Type* type = type_mgr->GetType(base_ptr->type_id());
+  assert(type->AsPointer());
+  type = type->AsPointer()->pointee_type();
+  std::vector<uint32_t> element_indices;
+  uint32_t starting_index = 1;
+  if (IsPtrAccessChain(inst->opcode())) {
+    // Skip the first index of OpPtrAccessChain as it does not affect type
+    // resolution.
+    starting_index = 2;
+  }
+  for (uint32_t i = starting_index; i < inst->NumInOperands(); ++i) {
+    Instruction* index_inst =
+        def_use_mgr->GetDef(inst->GetSingleWordInOperand(i));
+    const analysis::Constant* index_constant =
+        context()->get_constant_mgr()->GetConstantFromInst(index_inst);
+    if (index_constant) {
+      uint32_t index_value = GetConstantValue(index_constant);
+      element_indices.push_back(index_value);
+    } else {
+      // This index must not matter to resolve the type in valid SPIR-V.
+      element_indices.push_back(0);
+    }
+  }
+  type = type_mgr->GetMemberType(type, element_indices);
+  return type;
+}
+
+bool CombineAccessChains::CombineIndices(Instruction* ptr_input,
+                                         Instruction* inst,
+                                         std::vector<Operand>* new_operands) {
+  analysis::DefUseManager* def_use_mgr = context()->get_def_use_mgr();
+  analysis::ConstantManager* constant_mgr = context()->get_constant_mgr();
+
+  Instruction* last_index_inst = def_use_mgr->GetDef(
+      ptr_input->GetSingleWordInOperand(ptr_input->NumInOperands() - 1));
+  const analysis::Constant* last_index_constant =
+      constant_mgr->GetConstantFromInst(last_index_inst);
+
+  Instruction* element_inst =
+      def_use_mgr->GetDef(inst->GetSingleWordInOperand(1));
+  const analysis::Constant* element_constant =
+      constant_mgr->GetConstantFromInst(element_inst);
+
+  // Combine the last index of the AccessChain (|ptr_inst|) with the element
+  // operand of the PtrAccessChain (|inst|).
+  const bool combining_element_operands =
+      IsPtrAccessChain(inst->opcode()) &&
+      IsPtrAccessChain(ptr_input->opcode()) && ptr_input->NumInOperands() == 2;
+  uint32_t new_value_id = 0;
+  const analysis::Type* type = GetIndexedType(ptr_input);
+  if (last_index_constant && element_constant) {
+    // Combine the constants.
+    uint32_t new_value = GetConstantValue(last_index_constant) +
+                         GetConstantValue(element_constant);
+    const analysis::Constant* new_value_constant =
+        constant_mgr->GetConstant(last_index_constant->type(), {new_value});
+    Instruction* new_value_inst =
+        constant_mgr->GetDefiningInstruction(new_value_constant);
+    new_value_id = new_value_inst->result_id();
+  } else if (!type->AsStruct() || combining_element_operands) {
+    // Generate an addition of the two indices.
+    InstructionBuilder builder(
+        context(), inst,
+        IRContext::kAnalysisDefUse | IRContext::kAnalysisInstrToBlockMapping);
+    Instruction* addition = builder.AddIAdd(last_index_inst->type_id(),
+                                            last_index_inst->result_id(),
+                                            element_inst->result_id());
+    new_value_id = addition->result_id();
+  } else {
+    // Indexing into structs must be constant, so bail out here.
+    return false;
+  }
+  new_operands->push_back({SPV_OPERAND_TYPE_ID, {new_value_id}});
+  return true;
+}
+
+bool CombineAccessChains::CreateNewInputOperands(
+    Instruction* ptr_input, Instruction* inst,
+    std::vector<Operand>* new_operands) {
+  // Start by copying all the input operands of the feeder access chain.
+  for (uint32_t i = 0; i != ptr_input->NumInOperands() - 1; ++i) {
+    new_operands->push_back(ptr_input->GetInOperand(i));
+  }
+
+  // Deal with the last index of the feeder access chain.
+  if (IsPtrAccessChain(inst->opcode())) {
+    // The last index of the feeder should be combined with the element operand
+    // of |inst|.
+    if (!CombineIndices(ptr_input, inst, new_operands)) return false;
+  } else {
+    // The indices aren't being combined so now add the last index operand of
+    // |ptr_input|.
+    new_operands->push_back(
+        ptr_input->GetInOperand(ptr_input->NumInOperands() - 1));
+  }
+
+  // Copy the remaining index operands.
+  uint32_t starting_index = IsPtrAccessChain(inst->opcode()) ? 2 : 1;
+  for (uint32_t i = starting_index; i < inst->NumInOperands(); ++i) {
+    new_operands->push_back(inst->GetInOperand(i));
+  }
+
+  return true;
+}
+
+bool CombineAccessChains::CombineAccessChain(Instruction* inst) {
+  assert((inst->opcode() == SpvOpPtrAccessChain ||
+          inst->opcode() == SpvOpAccessChain ||
+          inst->opcode() == SpvOpInBoundsAccessChain ||
+          inst->opcode() == SpvOpInBoundsPtrAccessChain) &&
+         "Wrong opcode. Expected an access chain.");
+
+  Instruction* ptr_input =
+      context()->get_def_use_mgr()->GetDef(inst->GetSingleWordInOperand(0));
+  if (ptr_input->opcode() != SpvOpAccessChain &&
+      ptr_input->opcode() != SpvOpInBoundsAccessChain &&
+      ptr_input->opcode() != SpvOpPtrAccessChain &&
+      ptr_input->opcode() != SpvOpInBoundsPtrAccessChain) {
+    return false;
+  }
+
+  if (Has64BitIndices(inst) || Has64BitIndices(ptr_input)) return false;
+
+  // Handles the following cases:
+  // 1. |ptr_input| is an index-less access chain. Replace the pointer
+  //    in |inst| with |ptr_input|'s pointer.
+  // 2. |inst| is a index-less access chain. Change |inst| to an
+  //    OpCopyObject.
+  // 3. |inst| is not a pointer access chain.
+  //    |inst|'s indices are appended to |ptr_input|'s indices.
+  // 4. |ptr_input| is not pointer access chain.
+  //    |inst| is a pointer access chain.
+  //    |inst|'s element operand is combined with the last index in
+  //    |ptr_input| to form a new operand.
+  // 5. |ptr_input| is a pointer access chain.
+  //    Like the above scenario, |inst|'s element operand is combined
+  //    with |ptr_input|'s last index. This results is either a
+  //    combined element operand or combined regular index.
+
+  // TODO(alan-baker): Support this properly. Requires analyzing the
+  // size/alignment of the type and converting the stride into an element
+  // index.
+  uint32_t array_stride = GetArrayStride(ptr_input);
+  if (array_stride != 0) return false;
+
+  if (ptr_input->NumInOperands() == 1) {
+    // The input is effectively a no-op.
+    inst->SetInOperand(0, {ptr_input->GetSingleWordInOperand(0)});
+    context()->AnalyzeUses(inst);
+  } else if (inst->NumInOperands() == 1) {
+    // |inst| is a no-op, change it to a copy. Instruction simplification will
+    // clean it up.
+    inst->SetOpcode(SpvOpCopyObject);
+  } else {
+    std::vector<Operand> new_operands;
+    if (!CreateNewInputOperands(ptr_input, inst, &new_operands)) return false;
+
+    // Update the instruction.
+    inst->SetOpcode(UpdateOpcode(inst->opcode(), ptr_input->opcode()));
+    inst->SetInOperands(std::move(new_operands));
+    context()->AnalyzeUses(inst);
+  }
+  return true;
+}
+
+SpvOp CombineAccessChains::UpdateOpcode(SpvOp base_opcode, SpvOp input_opcode) {
+  auto IsInBounds = [](SpvOp opcode) {
+    return opcode == SpvOpInBoundsPtrAccessChain ||
+           opcode == SpvOpInBoundsAccessChain;
+  };
+
+  if (input_opcode == SpvOpInBoundsPtrAccessChain) {
+    if (!IsInBounds(base_opcode)) return SpvOpPtrAccessChain;
+  } else if (input_opcode == SpvOpInBoundsAccessChain) {
+    if (!IsInBounds(base_opcode)) return SpvOpAccessChain;
+  }
+
+  return input_opcode;
+}
+
+bool CombineAccessChains::IsPtrAccessChain(SpvOp opcode) {
+  return opcode == SpvOpPtrAccessChain || opcode == SpvOpInBoundsPtrAccessChain;
+}
+
+bool CombineAccessChains::Has64BitIndices(Instruction* inst) {
+  for (uint32_t i = 1; i < inst->NumInOperands(); ++i) {
+    Instruction* index_inst =
+        context()->get_def_use_mgr()->GetDef(inst->GetSingleWordInOperand(i));
+    const analysis::Type* index_type =
+        context()->get_type_mgr()->GetType(index_inst->type_id());
+    if (!index_type->AsInteger() || index_type->AsInteger()->width() != 32)
+      return true;
+  }
+  return false;
+}
+
+}  // namespace opt
+}  // namespace spvtools
diff --git a/source/opt/combine_access_chains.h b/source/opt/combine_access_chains.h
new file mode 100644
index 00000000..63027f12
--- /dev/null
+++ b/source/opt/combine_access_chains.h
@@ -0,0 +1,80 @@
+// Copyright (c) 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef LIBSPIRV_OPT_COMBINE_ACCESS_CHAINS_H_
+#define LIBSPIRV_OPT_COMBINE_ACCESS_CHAINS_H_
+
+#include "pass.h"
+
+namespace spvtools {
+namespace opt {
+
+// See optimizer.hpp for documentation.
+class CombineAccessChains : public Pass {
+ public:
+  const char* name() const override { return "combine-access-chains"; }
+  Status Process() override;
+
+  IRContext::Analysis GetPreservedAnalyses() override {
+    return IRContext::kAnalysisDefUse |
+           IRContext::kAnalysisInstrToBlockMapping |
+           IRContext::kAnalysisDecorations | IRContext::kAnalysisCombinators |
+           IRContext::kAnalysisCFG | IRContext::kAnalysisDominatorAnalysis |
+           IRContext::kAnalysisNameMap;
+  }
+
+ private:
+  // Combine access chains in |function|. Blocks are processed in reverse
+  // post-order. Returns true if the function is modified.
+  bool ProcessFunction(Function& function);
+
+  // Combines an access chain (normal, in bounds or pointer) |inst| if its base
+  // pointer is another access chain. Returns true if the access chain was
+  // modified.
+  bool CombineAccessChain(Instruction* inst);
+
+  // Returns the value of |constant_inst| as a uint32_t.
+  uint32_t GetConstantValue(const analysis::Constant* constant_inst);
+
+  // Returns the array stride of |inst|'s type.
+  uint32_t GetArrayStride(const Instruction* inst);
+
+  // Returns the type by resolving the index operands |inst|. |inst| must be an
+  // access chain instruction.
+  const analysis::Type* GetIndexedType(Instruction* inst);
+
+  // Populates |new_operands| with the operands for the combined access chain.
+  // Returns false if the access chains cannot be combined.
+  bool CreateNewInputOperands(Instruction* ptr_input, Instruction* inst,
+                              std::vector<Operand>* new_operands);
+
+  // Combines the last index of |ptr_input| with the element operand of |inst|.
+  // Adds the combined operand to |new_operands|.
+  bool CombineIndices(Instruction* ptr_input, Instruction* inst,
+                      std::vector<Operand>* new_operands);
+
+  // Returns the opcode to use for the combined access chain.
+  SpvOp UpdateOpcode(SpvOp base_opcode, SpvOp input_opcode);
+
+  // Returns true if |opcode| is a pointer access chain.
+  bool IsPtrAccessChain(SpvOp opcode);
+
+  // Returns true if |inst| (an access chain) has 64-bit indices.
+  bool Has64BitIndices(Instruction* inst);
+};
+
+}  // namespace opt
+}  // namespace spvtools
+
+#endif  // LIBSPIRV_OPT_COMBINE_ACCESS_CHAINS_H_
diff --git a/source/opt/folding_rules.cpp b/source/opt/folding_rules.cpp
index c3daa6fc..7faa3610 100644
--- a/source/opt/folding_rules.cpp
+++ b/source/opt/folding_rules.cpp
@@ -1907,6 +1907,37 @@ FoldingRule RedundantFMix() {
   };
 }
 
+// This rule handles addition of zero for integers.
+FoldingRule RedundantIAdd() {
+  return [](IRContext* context, Instruction* inst,
+            const std::vector<const analysis::Constant*>& constants) {
+    assert(inst->opcode() == SpvOpIAdd && "Wrong opcode. Should be OpIAdd.");
+
+    uint32_t operand = std::numeric_limits<uint32_t>::max();
+    const analysis::Type* operand_type = nullptr;
+    if (constants[0] && constants[0]->IsZero()) {
+      operand = inst->GetSingleWordInOperand(1);
+      operand_type = constants[0]->type();
+    } else if (constants[1] && constants[1]->IsZero()) {
+      operand = inst->GetSingleWordInOperand(0);
+      operand_type = constants[1]->type();
+    }
+
+    if (operand != std::numeric_limits<uint32_t>::max()) {
+      const analysis::Type* inst_type =
+          context->get_type_mgr()->GetType(inst->type_id());
+      if (inst_type->IsSame(operand_type)) {
+        inst->SetOpcode(SpvOpCopyObject);
+      } else {
+        inst->SetOpcode(SpvOpBitcast);
+      }
+      inst->SetInOperands({{SPV_OPERAND_TYPE_ID, {operand}}});
+      return true;
+    }
+    return false;
+  };
+}
+
 // This rule look for a dot with a constant vector containing a single 1 and
 // the rest 0s.  This is the same as doing an extract.
 FoldingRule DotProductDoingExtract() {
@@ -2177,6 +2208,7 @@ FoldingRules::FoldingRules() {
   rules_[SpvOpFSub].push_back(MergeSubAddArithmetic());
   rules_[SpvOpFSub].push_back(MergeSubSubArithmetic());
 
+  rules_[SpvOpIAdd].push_back(RedundantIAdd());
   rules_[SpvOpIAdd].push_back(MergeAddNegateArithmetic());
   rules_[SpvOpIAdd].push_back(MergeAddAddArithmetic());
   rules_[SpvOpIAdd].push_back(MergeAddSubArithmetic());
diff --git a/source/opt/optimizer.cpp b/source/opt/optimizer.cpp
index f91e80bd..60791ca0 100644
--- a/source/opt/optimizer.cpp
+++ b/source/opt/optimizer.cpp
@@ -159,6 +159,7 @@ Optimizer& Optimizer::RegisterPerformancePasses() {
       .RegisterPass(CreateCCPPass())
       .RegisterPass(CreateAggressiveDCEPass())
       .RegisterPass(CreateRedundancyEliminationPass())
+      .RegisterPass(CreateCombineAccessChainsPass())
       .RegisterPass(CreateSimplificationPass())
       .RegisterPass(CreateVectorDCEPass())
       .RegisterPass(CreateDeadInsertElimPass())
@@ -303,6 +304,8 @@ bool Optimizer::RegisterPassFromFlag(const std::string& flag) {
     RegisterPass(CreateInlineExhaustivePass());
   } else if (pass_name == "inline-entry-points-opaque") {
     RegisterPass(CreateInlineOpaquePass());
+  } else if (pass_name == "combine-access-chains") {
+    RegisterPass(CreateCombineAccessChainsPass());
   } else if (pass_name == "convert-local-access-chains") {
     RegisterPass(CreateLocalAccessChainConvertPass());
   } else if (pass_name == "eliminate-dead-code-aggressive") {
@@ -710,4 +713,9 @@ Optimizer::PassToken CreateReduceLoadSizePass() {
   return MakeUnique<Optimizer::PassToken::Impl>(
       MakeUnique<opt::ReduceLoadSize>());
 }
+
+Optimizer::PassToken CreateCombineAccessChainsPass() {
+  return MakeUnique<Optimizer::PassToken::Impl>(
+      MakeUnique<opt::CombineAccessChains>());
+}
 }  // namespace spvtools
diff --git a/source/opt/passes.h b/source/opt/passes.h
index 07419de4..8931b47a 100644
--- a/source/opt/passes.h
+++ b/source/opt/passes.h
@@ -21,6 +21,7 @@
 #include "block_merge_pass.h"
 #include "ccp_pass.h"
 #include "cfg_cleanup_pass.h"
+#include "combine_access_chains.h"
 #include "common_uniform_elim_pass.h"
 #include "compact_ids_pass.h"
 #include "copy_prop_arrays.h"
diff --git a/test/opt/CMakeLists.txt b/test/opt/CMakeLists.txt
index a0b37901..f2741f67 100644
--- a/test/opt/CMakeLists.txt
+++ b/test/opt/CMakeLists.txt
@@ -332,3 +332,8 @@ add_spvtools_unittest(TARGET constant_manager
   LIBS SPIRV-Tools-opt
 )
 
+add_spvtools_unittest(TARGET combine_access_chains
+  SRCS combine_access_chains_test.cpp
+  LIBS SPIRV-Tools-opt
+)
+
diff --git a/test/opt/combine_access_chains_test.cpp b/test/opt/combine_access_chains_test.cpp
new file mode 100644
index 00000000..a9ed9104
--- /dev/null
+++ b/test/opt/combine_access_chains_test.cpp
@@ -0,0 +1,752 @@
+// Copyright (c) 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "assembly_builder.h"
+#include "gmock/gmock.h"
+#include "pass_fixture.h"
+#include "pass_utils.h"
+
+namespace spvtools {
+namespace opt {
+namespace {
+
+using CombineAccessChainsTest = PassTest<::testing::Test>;
+
+#ifdef SPIRV_EFFCEE
+TEST_F(CombineAccessChainsTest, PtrAccessChainFromAccessChainConstant) {
+  const std::string text = R"(
+; CHECK: [[int:%\w+]] = OpTypeInt 32 0
+; CHECK: [[int3:%\w+]] = OpConstant [[int]] 3
+; CHECK: [[ptr_int:%\w+]] = OpTypePointer Workgroup [[int]]
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: OpAccessChain [[ptr_int]] [[var]] [[int3]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_3 = OpConstant %uint 3
+%uint_4 = OpConstant %uint 4
+%uint_array_4 = OpTypeArray %uint %uint_4
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Workgroup_uint_array_4 = OpTypePointer Workgroup %uint_array_4
+%var = OpVariable %ptr_Workgroup_uint_array_4 Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%main_lab = OpLabel
+%gep = OpAccessChain %ptr_Workgroup_uint %var %uint_0
+%ptr_gep = OpPtrAccessChain %ptr_Workgroup_uint %gep %uint_3
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest, PtrAccessChainFromInBoundsAccessChainConstant) {
+  const std::string text = R"(
+; CHECK: [[int:%\w+]] = OpTypeInt 32 0
+; CHECK: [[int3:%\w+]] = OpConstant [[int]] 3
+; CHECK: [[ptr_int:%\w+]] = OpTypePointer Workgroup [[int]]
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: OpAccessChain [[ptr_int]] [[var]] [[int3]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_3 = OpConstant %uint 3
+%uint_4 = OpConstant %uint 4
+%uint_array_4 = OpTypeArray %uint %uint_4
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Workgroup_uint_array_4 = OpTypePointer Workgroup %uint_array_4
+%var = OpVariable %ptr_Workgroup_uint_array_4 Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%main_lab = OpLabel
+%gep = OpInBoundsAccessChain %ptr_Workgroup_uint %var %uint_0
+%ptr_gep = OpPtrAccessChain %ptr_Workgroup_uint %gep %uint_3
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest, PtrAccessChainFromAccessChainCombineConstant) {
+  const std::string text = R"(
+; CHECK: [[int:%\w+]] = OpTypeInt 32 0
+; CHECK: [[ptr_int:%\w+]] = OpTypePointer Workgroup [[int]]
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: [[int2:%\w+]] = OpConstant [[int]] 2
+; CHECK: OpAccessChain [[ptr_int]] [[var]] [[int2]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_1 = OpConstant %uint 1
+%uint_4 = OpConstant %uint 4
+%uint_array_4 = OpTypeArray %uint %uint_4
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Workgroup_uint_array_4 = OpTypePointer Workgroup %uint_array_4
+%var = OpVariable %ptr_Workgroup_uint_array_4 Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%main_lab = OpLabel
+%gep = OpAccessChain %ptr_Workgroup_uint %var %uint_1
+%ptr_gep = OpPtrAccessChain %ptr_Workgroup_uint %gep %uint_1
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest, PtrAccessChainFromAccessChainNonConstant) {
+  const std::string text = R"(
+; CHECK: [[int:%\w+]] = OpTypeInt 32 0
+; CHECK: [[ptr_int:%\w+]] = OpTypePointer Workgroup [[int]]
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: [[ld1:%\w+]] = OpLoad
+; CHECK: [[ld2:%\w+]] = OpLoad
+; CHECK: [[add:%\w+]] = OpIAdd [[int]] [[ld1]] [[ld2]]
+; CHECK: OpAccessChain [[ptr_int]] [[var]] [[add]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_4 = OpConstant %uint 4
+%uint_array_4 = OpTypeArray %uint %uint_4
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Function_uint = OpTypePointer Function %uint
+%ptr_Workgroup_uint_array_4 = OpTypePointer Workgroup %uint_array_4
+%var = OpVariable %ptr_Workgroup_uint_array_4 Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%main_lab = OpLabel
+%local_var = OpVariable %ptr_Function_uint Function
+%ld1 = OpLoad %uint %local_var
+%gep = OpAccessChain %ptr_Workgroup_uint %var %ld1
+%ld2 = OpLoad %uint %local_var
+%ptr_gep = OpPtrAccessChain %ptr_Workgroup_uint %gep %ld2
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest, PtrAccessChainFromAccessChainExtraIndices) {
+  const std::string text = R"(
+; CHECK: [[int:%\w+]] = OpTypeInt 32 0
+; CHECK: [[int1:%\w+]] = OpConstant [[int]] 1
+; CHECK: [[int2:%\w+]] = OpConstant [[int]] 2
+; CHECK: [[int3:%\w+]] = OpConstant [[int]] 3
+; CHECK: [[ptr_int:%\w+]] = OpTypePointer Workgroup [[int]]
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: OpAccessChain [[ptr_int]] [[var]] [[int1]] [[int2]] [[int3]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_1 = OpConstant %uint 1
+%uint_2 = OpConstant %uint 2
+%uint_3 = OpConstant %uint 3
+%uint_4 = OpConstant %uint 4
+%uint_array_4 = OpTypeArray %uint %uint_4
+%uint_array_4_array_4 = OpTypeArray %uint_array_4 %uint_4
+%uint_array_4_array_4_array_4 = OpTypeArray %uint_array_4_array_4 %uint_4
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Function_uint = OpTypePointer Function %uint
+%ptr_Workgroup_uint_array_4 = OpTypePointer Workgroup %uint_array_4
+%ptr_Workgroup_uint_array_4_array_4 = OpTypePointer Workgroup %uint_array_4_array_4
+%ptr_Workgroup_uint_array_4_array_4_array_4 = OpTypePointer Workgroup %uint_array_4_array_4_array_4
+%var = OpVariable %ptr_Workgroup_uint_array_4_array_4_array_4 Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%main_lab = OpLabel
+%gep = OpAccessChain %ptr_Workgroup_uint_array_4 %var %uint_1 %uint_0
+%ptr_gep = OpPtrAccessChain %ptr_Workgroup_uint %gep %uint_2 %uint_3
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest,
+       PtrAccessChainFromPtrAccessChainCombineElementOperand) {
+  const std::string text = R"(
+; CHECK: [[int:%\w+]] = OpTypeInt 32 0
+; CHECK: [[int3:%\w+]] = OpConstant [[int]] 3
+; CHECK: [[ptr_int:%\w+]] = OpTypePointer Workgroup [[int]]
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: [[int6:%\w+]] = OpConstant [[int]] 6
+; CHECK: OpPtrAccessChain [[ptr_int]] [[var]] [[int6]] [[int3]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_3 = OpConstant %uint 3
+%uint_4 = OpConstant %uint 4
+%uint_array_4 = OpTypeArray %uint %uint_4
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Workgroup_uint_array_4 = OpTypePointer Workgroup %uint_array_4
+%var = OpVariable %ptr_Workgroup_uint_array_4 Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%main_lab = OpLabel
+%gep = OpPtrAccessChain %ptr_Workgroup_uint_array_4 %var %uint_3
+%ptr_gep = OpPtrAccessChain %ptr_Workgroup_uint %gep %uint_3 %uint_3
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest,
+       PtrAccessChainFromPtrAccessChainOnlyElementOperand) {
+  const std::string text = R"(
+; CHECK: [[int:%\w+]] = OpTypeInt 32 0
+; CHECK: [[int4:%\w+]] = OpConstant [[int]] 4
+; CHECK: [[array:%\w+]] = OpTypeArray [[int]] [[int4]]
+; CHECK: [[ptr_array:%\w+]] = OpTypePointer Workgroup [[array]]
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: [[int6:%\w+]] = OpConstant [[int]] 6
+; CHECK: OpPtrAccessChain [[ptr_array]] [[var]] [[int6]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_3 = OpConstant %uint 3
+%uint_4 = OpConstant %uint 4
+%uint_array_4 = OpTypeArray %uint %uint_4
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Workgroup_uint_array_4 = OpTypePointer Workgroup %uint_array_4
+%var = OpVariable %ptr_Workgroup_uint_array_4 Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%main_lab = OpLabel
+%gep = OpPtrAccessChain %ptr_Workgroup_uint_array_4 %var %uint_3
+%ptr_gep = OpPtrAccessChain %ptr_Workgroup_uint_array_4 %gep %uint_3
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest,
+       PtrAccessChainFromPtrAccessCombineNonElementIndex) {
+  const std::string text = R"(
+; CHECK: [[int:%\w+]] = OpTypeInt 32 0
+; CHECK: [[int3:%\w+]] = OpConstant [[int]] 3
+; CHECK: [[ptr_int:%\w+]] = OpTypePointer Workgroup [[int]]
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: OpPtrAccessChain [[ptr_int]] [[var]] [[int3]] [[int3]] [[int3]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_3 = OpConstant %uint 3
+%uint_4 = OpConstant %uint 4
+%uint_array_4 = OpTypeArray %uint %uint_4
+%uint_array_4_array_4 = OpTypeArray %uint_array_4 %uint_4
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Function_uint = OpTypePointer Function %uint
+%ptr_Workgroup_uint_array_4 = OpTypePointer Workgroup %uint_array_4
+%ptr_Workgroup_uint_array_4_array_4 = OpTypePointer Workgroup %uint_array_4_array_4
+%var = OpVariable %ptr_Workgroup_uint_array_4_array_4 Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%main_lab = OpLabel
+%gep = OpPtrAccessChain %ptr_Workgroup_uint_array_4 %var %uint_3 %uint_0
+%ptr_gep = OpPtrAccessChain %ptr_Workgroup_uint %gep %uint_3 %uint_3
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest,
+       AccessChainFromPtrAccessChainOnlyElementOperand) {
+  const std::string text = R"(
+; CHECK: [[int:%\w+]] = OpTypeInt 32 0
+; CHECK: [[int3:%\w+]] = OpConstant [[int]] 3
+; CHECK: [[ptr_int:%\w+]] = OpTypePointer Workgroup [[int]]
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: OpPtrAccessChain [[ptr_int]] [[var]] [[int3]] [[int3]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_3 = OpConstant %uint 3
+%uint_4 = OpConstant %uint 4
+%uint_array_4 = OpTypeArray %uint %uint_4
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Workgroup_uint_array_4 = OpTypePointer Workgroup %uint_array_4
+%var = OpVariable %ptr_Workgroup_uint_array_4 Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%main_lab = OpLabel
+%ptr_gep = OpPtrAccessChain %ptr_Workgroup_uint_array_4 %var %uint_3
+%gep = OpAccessChain %ptr_Workgroup_uint %ptr_gep %uint_3
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest, AccessChainFromPtrAccessChainAppend) {
+  const std::string text = R"(
+; CHECK: [[int:%\w+]] = OpTypeInt 32 0
+; CHECK: [[int1:%\w+]] = OpConstant [[int]] 1
+; CHECK: [[int2:%\w+]] = OpConstant [[int]] 2
+; CHECK: [[int3:%\w+]] = OpConstant [[int]] 3
+; CHECK: [[ptr_int:%\w+]] = OpTypePointer Workgroup [[int]]
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: OpPtrAccessChain [[ptr_int]] [[var]] [[int1]] [[int2]] [[int3]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_1 = OpConstant %uint 1
+%uint_2 = OpConstant %uint 2
+%uint_3 = OpConstant %uint 3
+%uint_4 = OpConstant %uint 4
+%uint_array_4 = OpTypeArray %uint %uint_4
+%uint_array_4_array_4 = OpTypeArray %uint_array_4 %uint_4
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Workgroup_uint_array_4 = OpTypePointer Workgroup %uint_array_4
+%ptr_Workgroup_uint_array_4_array_4 = OpTypePointer Workgroup %uint_array_4_array_4
+%var = OpVariable %ptr_Workgroup_uint_array_4_array_4 Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%main_lab = OpLabel
+%ptr_gep = OpPtrAccessChain %ptr_Workgroup_uint_array_4 %var %uint_1 %uint_2
+%gep = OpAccessChain %ptr_Workgroup_uint %ptr_gep %uint_3
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest, AccessChainFromAccessChainAppend) {
+  const std::string text = R"(
+; CHECK: [[int:%\w+]] = OpTypeInt 32 0
+; CHECK: [[int1:%\w+]] = OpConstant [[int]] 1
+; CHECK: [[int2:%\w+]] = OpConstant [[int]] 2
+; CHECK: [[ptr_int:%\w+]] = OpTypePointer Workgroup [[int]]
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: OpAccessChain [[ptr_int]] [[var]] [[int1]] [[int2]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_1 = OpConstant %uint 1
+%uint_2 = OpConstant %uint 2
+%uint_3 = OpConstant %uint 3
+%uint_4 = OpConstant %uint 4
+%uint_array_4 = OpTypeArray %uint %uint_4
+%uint_array_4_array_4 = OpTypeArray %uint_array_4 %uint_4
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Workgroup_uint_array_4 = OpTypePointer Workgroup %uint_array_4
+%ptr_Workgroup_uint_array_4_array_4 = OpTypePointer Workgroup %uint_array_4_array_4
+%var = OpVariable %ptr_Workgroup_uint_array_4_array_4 Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%main_lab = OpLabel
+%ptr_gep = OpAccessChain %ptr_Workgroup_uint_array_4 %var %uint_1
+%gep = OpAccessChain %ptr_Workgroup_uint %ptr_gep %uint_2
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest, NonConstantStructSlide) {
+  const std::string text = R"(
+; CHECK: [[int0:%\w+]] = OpConstant {{%\w+}} 0
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: [[ld:%\w+]] = OpLoad
+; CHECK: OpPtrAccessChain {{%\w+}} [[var]] [[ld]] [[int0]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%struct = OpTypeStruct %uint %uint
+%ptr_Workgroup_struct = OpTypePointer Workgroup %struct
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Function_uint = OpTypePointer Function %uint
+%wg_var = OpVariable %ptr_Workgroup_struct Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%1 = OpLabel
+%func_var = OpVariable %ptr_Function_uint Function
+%ld = OpLoad %uint %func_var
+%ptr_gep = OpPtrAccessChain %ptr_Workgroup_struct %wg_var %ld
+%gep = OpAccessChain %ptr_Workgroup_uint %ptr_gep %uint_0
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest, DontCombineNonConstantStructSlide) {
+  const std::string text = R"(
+; CHECK: [[int0:%\w+]] = OpConstant {{%\w+}} 0
+; CHECK: [[ld:%\w+]] = OpLoad
+; CHECK: [[gep:%\w+]] = OpAccessChain
+; CHECK: OpPtrAccessChain {{%\w+}} [[gep]] [[ld]] [[int0]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_4 = OpConstant %uint 4
+%struct = OpTypeStruct %uint %uint
+%struct_array_4 = OpTypeArray %struct %uint_4
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Function_uint = OpTypePointer Function %uint
+%ptr_Workgroup_struct = OpTypePointer Workgroup %struct
+%ptr_Workgroup_struct_array_4 = OpTypePointer Workgroup %struct_array_4
+%wg_var = OpVariable %ptr_Workgroup_struct_array_4 Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%1 = OpLabel
+%func_var = OpVariable %ptr_Function_uint Function
+%ld = OpLoad %uint %func_var
+%gep = OpAccessChain %ptr_Workgroup_struct %wg_var %uint_0
+%ptr_gep = OpPtrAccessChain %ptr_Workgroup_uint %gep %ld %uint_0
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest, CombineNonConstantStructSlideElement) {
+  const std::string text = R"(
+; CHECK: [[int0:%\w+]] = OpConstant {{%\w+}} 0
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: [[ld:%\w+]] = OpLoad
+; CHECK: [[add:%\w+]] = OpIAdd {{%\w+}} [[ld]] [[ld]]
+; CHECK: OpPtrAccessChain {{%\w+}} [[var]] [[add]] [[int0]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_4 = OpConstant %uint 4
+%struct = OpTypeStruct %uint %uint
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Function_uint = OpTypePointer Function %uint
+%ptr_Workgroup_struct = OpTypePointer Workgroup %struct
+%wg_var = OpVariable %ptr_Workgroup_struct Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%1 = OpLabel
+%func_var = OpVariable %ptr_Function_uint Function
+%ld = OpLoad %uint %func_var
+%gep = OpPtrAccessChain %ptr_Workgroup_struct %wg_var %ld
+%ptr_gep = OpPtrAccessChain %ptr_Workgroup_uint %gep %ld %uint_0
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest, PtrAccessChainFromInBoundsPtrAccessChain) {
+  const std::string text = R"(
+; CHECK: [[int:%\w+]] = OpTypeInt 32 0
+; CHECK: [[int4:%\w+]] = OpConstant [[int]] 4
+; CHECK: [[array:%\w+]] = OpTypeArray [[int]] [[int4]]
+; CHECK: [[ptr_array:%\w+]] = OpTypePointer Workgroup [[array]]
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: [[int6:%\w+]] = OpConstant [[int]] 6
+; CHECK: OpPtrAccessChain [[ptr_array]] [[var]] [[int6]]
+OpCapability Shader
+OpCapability VariablePointers
+OpCapability Addresses
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_3 = OpConstant %uint 3
+%uint_4 = OpConstant %uint 4
+%uint_array_4 = OpTypeArray %uint %uint_4
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Workgroup_uint_array_4 = OpTypePointer Workgroup %uint_array_4
+%var = OpVariable %ptr_Workgroup_uint_array_4 Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%main_lab = OpLabel
+%gep = OpInBoundsPtrAccessChain %ptr_Workgroup_uint_array_4 %var %uint_3
+%ptr_gep = OpPtrAccessChain %ptr_Workgroup_uint_array_4 %gep %uint_3
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest, InBoundsPtrAccessChainFromPtrAccessChain) {
+  const std::string text = R"(
+; CHECK: [[int:%\w+]] = OpTypeInt 32 0
+; CHECK: [[int4:%\w+]] = OpConstant [[int]] 4
+; CHECK: [[array:%\w+]] = OpTypeArray [[int]] [[int4]]
+; CHECK: [[ptr_array:%\w+]] = OpTypePointer Workgroup [[array]]
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: [[int6:%\w+]] = OpConstant [[int]] 6
+; CHECK: OpPtrAccessChain [[ptr_array]] [[var]] [[int6]]
+OpCapability Shader
+OpCapability VariablePointers
+OpCapability Addresses
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_3 = OpConstant %uint 3
+%uint_4 = OpConstant %uint 4
+%uint_array_4 = OpTypeArray %uint %uint_4
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Workgroup_uint_array_4 = OpTypePointer Workgroup %uint_array_4
+%var = OpVariable %ptr_Workgroup_uint_array_4 Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%main_lab = OpLabel
+%gep = OpPtrAccessChain %ptr_Workgroup_uint_array_4 %var %uint_3
+%ptr_gep = OpInBoundsPtrAccessChain %ptr_Workgroup_uint_array_4 %gep %uint_3
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest,
+       InBoundsPtrAccessChainFromInBoundsPtrAccessChain) {
+  const std::string text = R"(
+; CHECK: [[int:%\w+]] = OpTypeInt 32 0
+; CHECK: [[int4:%\w+]] = OpConstant [[int]] 4
+; CHECK: [[array:%\w+]] = OpTypeArray [[int]] [[int4]]
+; CHECK: [[ptr_array:%\w+]] = OpTypePointer Workgroup [[array]]
+; CHECK: [[var:%\w+]] = OpVariable {{%\w+}} Workgroup
+; CHECK: [[int6:%\w+]] = OpConstant [[int]] 6
+; CHECK: OpInBoundsPtrAccessChain [[ptr_array]] [[var]] [[int6]]
+OpCapability Shader
+OpCapability VariablePointers
+OpCapability Addresses
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%uint_3 = OpConstant %uint 3
+%uint_4 = OpConstant %uint 4
+%uint_array_4 = OpTypeArray %uint %uint_4
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%ptr_Workgroup_uint_array_4 = OpTypePointer Workgroup %uint_array_4
+%var = OpVariable %ptr_Workgroup_uint_array_4 Workgroup
+%void_func = OpTypeFunction %void
+%main = OpFunction %void None %void_func
+%main_lab = OpLabel
+%gep = OpInBoundsPtrAccessChain %ptr_Workgroup_uint_array_4 %var %uint_3
+%ptr_gep = OpInBoundsPtrAccessChain %ptr_Workgroup_uint_array_4 %gep %uint_3
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest, NoIndexAccessChains) {
+  const std::string text = R"(
+; CHECK: [[var:%\w+]] = OpVariable
+; CHECK-NOT: OpConstant
+; CHECK: [[gep:%\w+]] = OpAccessChain {{%\w+}} [[var]]
+; CHECK: OpAccessChain {{%\w+}} [[var]]
+OpCapability Shader
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %func "func"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%var = OpVariable %ptr_Workgroup_uint Workgroup
+%void_func = OpTypeFunction %void
+%func = OpFunction %void None %void_func
+%1 = OpLabel
+%gep1 = OpAccessChain %ptr_Workgroup_uint %var
+%gep2 = OpAccessChain %ptr_Workgroup_uint %gep1
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest, NoIndexPtrAccessChains) {
+  const std::string text = R"(
+; CHECK: [[int0:%\w+]] = OpConstant {{%\w+}} 0
+; CHECK: [[var:%\w+]] = OpVariable
+; CHECK: [[gep:%\w+]] = OpPtrAccessChain {{%\w+}} [[var]] [[int0]]
+; CHECK: OpCopyObject {{%\w+}} [[gep]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %func "func"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%var = OpVariable %ptr_Workgroup_uint Workgroup
+%void_func = OpTypeFunction %void
+%func = OpFunction %void None %void_func
+%1 = OpLabel
+%gep1 = OpPtrAccessChain %ptr_Workgroup_uint %var %uint_0
+%gep2 = OpAccessChain %ptr_Workgroup_uint %gep1
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest, NoIndexPtrAccessChains2) {
+  const std::string text = R"(
+; CHECK: [[int0:%\w+]] = OpConstant {{%\w+}} 0
+; CHECK: [[var:%\w+]] = OpVariable
+; CHECK: OpPtrAccessChain {{%\w+}} [[var]] [[int0]]
+OpCapability Shader
+OpCapability VariablePointers
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %func "func"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%uint_0 = OpConstant %uint 0
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%var = OpVariable %ptr_Workgroup_uint Workgroup
+%void_func = OpTypeFunction %void
+%func = OpFunction %void None %void_func
+%1 = OpLabel
+%gep1 = OpAccessChain %ptr_Workgroup_uint %var
+%gep2 = OpPtrAccessChain %ptr_Workgroup_uint %gep1 %uint_0
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+
+TEST_F(CombineAccessChainsTest, CombineMixedSign) {
+  const std::string text = R"(
+; CHECK: [[uint:%\w+]] = OpTypeInt 32 0
+; CHECK: [[var:%\w+]] = OpVariable
+; CHECK: [[uint2:%\w+]] = OpConstant [[uint]] 2
+; CHECK: OpInBoundsPtrAccessChain {{%\w+}} [[var]] [[uint2]]
+OpCapability Shader
+OpCapability VariablePointers
+OpCapability Addresses
+OpExtension "SPV_KHR_variable_pointers"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %func "func"
+%void = OpTypeVoid
+%uint = OpTypeInt 32 0
+%int = OpTypeInt 32 1
+%uint_1 = OpConstant %uint 1
+%int_1 = OpConstant %int 1
+%ptr_Workgroup_uint = OpTypePointer Workgroup %uint
+%var = OpVariable %ptr_Workgroup_uint Workgroup
+%void_func = OpTypeFunction %void
+%func = OpFunction %void None %void_func
+%1 = OpLabel
+%gep1 = OpInBoundsPtrAccessChain %ptr_Workgroup_uint %var %uint_1
+%gep2 = OpInBoundsPtrAccessChain %ptr_Workgroup_uint %gep1 %int_1
+OpReturn
+OpFunctionEnd
+)";
+
+  SinglePassRunAndMatch<CombineAccessChains>(text, true);
+}
+#endif  // SPIRV_EFFCEE
+
+}  // namespace
+}  // namespace opt
+}  // namespace spvtools
diff --git a/test/opt/fold_test.cpp b/test/opt/fold_test.cpp
index 9a870a6e..e4a52c71 100644
--- a/test/opt/fold_test.cpp
+++ b/test/opt/fold_test.cpp
@@ -162,6 +162,7 @@ OpName %main "main"
 %_ptr_v2float = OpTypePointer Function %v2float
 %_ptr_v2double = OpTypePointer Function %v2double
 %short_0 = OpConstant %short 0
+%short_2 = OpConstant %short 2
 %short_3 = OpConstant %short 3
 %100 = OpConstant %int 0 ; Need a def with an numerical id to define id maps.
 %103 = OpConstant %int 7 ; Need a def with an numerical id to define id maps.
@@ -176,12 +177,15 @@ OpName %main "main"
 %long_2 = OpConstant %long 2
 %long_3 = OpConstant %long 3
 %uint_0 = OpConstant %uint 0
+%uint_1 = OpConstant %uint 1
 %uint_2 = OpConstant %uint 2
 %uint_3 = OpConstant %uint 3
 %uint_4 = OpConstant %uint 4
 %uint_32 = OpConstant %uint 32
 %uint_max = OpConstant %uint 4294967295
 %v2int_undef = OpUndef %v2int
+%v2int_0_0 = OpConstantComposite %v2int %int_0 %int_0
+%v2int_1_0 = OpConstantComposite %v2int %int_1 %int_0
 %v2int_2_2 = OpConstantComposite %v2int %int_2 %int_2
 %v2int_2_3 = OpConstantComposite %v2int %int_2 %int_3
 %v2int_3_2 = OpConstantComposite %v2int %int_3 %int_2
@@ -2589,19 +2593,19 @@ INSTANTIATE_TEST_CASE_P(IntegerArithmeticTestCases, GeneralInstructionFoldingTes
             "OpReturn\n" +
             "OpFunctionEnd",
         2, 0),
-    // Test case 38: Don't fold 0 + 3 (long), bad length
+    // Test case 38: Don't fold 2 + 3 (long), bad length
     InstructionFoldingCase<uint32_t>(
         Header() + "%main = OpFunction %void None %void_func\n" +
             "%main_lab = OpLabel\n" +
-            "%2 = OpIAdd %long %long_0 %long_3\n" +
+            "%2 = OpIAdd %long %long_2 %long_3\n" +
             "OpReturn\n" +
             "OpFunctionEnd",
         2, 0),
-    // Test case 39: Don't fold 0 + 3 (short), bad length
+    // Test case 39: Don't fold 2 + 3 (short), bad length
     InstructionFoldingCase<uint32_t>(
         Header() + "%main = OpFunction %void None %void_func\n" +
             "%main_lab = OpLabel\n" +
-            "%2 = OpIAdd %short %short_0 %short_3\n" +
+            "%2 = OpIAdd %short %short_2 %short_3\n" +
             "OpReturn\n" +
             "OpFunctionEnd",
         2, 0),
@@ -3326,6 +3330,90 @@ INSTANTIATE_TEST_CASE_P(DoubleVectorRedundantFoldingTest, GeneralInstructionFold
         2, 3)
 ));
 
+INSTANTIATE_TEST_CASE_P(IntegerRedundantFoldingTest, GeneralInstructionFoldingTest,
+                        ::testing::Values(
+    // Test case 0: Don't fold n + 1
+    InstructionFoldingCase<uint32_t>(
+        Header() + "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%n = OpVariable %_ptr_uint Function\n" +
+            "%3 = OpLoad %uint %n\n" +
+            "%2 = OpIAdd %uint %3 %uint_1\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd",
+        2, 0),
+    // Test case 1: Don't fold 1 + n
+    InstructionFoldingCase<uint32_t>(
+        Header() + "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%n = OpVariable %_ptr_uint Function\n" +
+            "%3 = OpLoad %uint %n\n" +
+            "%2 = OpIAdd %uint %uint_1 %3\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd",
+        2, 0),
+    // Test case 2: Fold n + 0
+    InstructionFoldingCase<uint32_t>(
+        Header() + "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%n = OpVariable %_ptr_uint Function\n" +
+            "%3 = OpLoad %uint %n\n" +
+            "%2 = OpIAdd %uint %3 %uint_0\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd",
+        2, 3),
+    // Test case 3: Fold 0 + n
+    InstructionFoldingCase<uint32_t>(
+        Header() + "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%n = OpVariable %_ptr_uint Function\n" +
+            "%3 = OpLoad %uint %n\n" +
+            "%2 = OpIAdd %uint %uint_0 %3\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd",
+        2, 3),
+    // Test case 4: Don't fold n + (1,0)
+    InstructionFoldingCase<uint32_t>(
+        Header() + "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%n = OpVariable %_ptr_v2int Function\n" +
+            "%3 = OpLoad %v2int %n\n" +
+            "%2 = OpIAdd %v2int %3 %v2int_1_0\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd",
+        2, 0),
+    // Test case 5: Don't fold (1,0) + n
+    InstructionFoldingCase<uint32_t>(
+        Header() + "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%n = OpVariable %_ptr_v2int Function\n" +
+            "%3 = OpLoad %v2int %n\n" +
+            "%2 = OpIAdd %v2int %v2int_1_0 %3\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd",
+        2, 0),
+    // Test case 6: Fold n + (0,0)
+    InstructionFoldingCase<uint32_t>(
+        Header() + "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%n = OpVariable %_ptr_v2int Function\n" +
+            "%3 = OpLoad %v2int %n\n" +
+            "%2 = OpIAdd %v2int %3 %v2int_0_0\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd",
+        2, 3),
+    // Test case 7: Fold (0,0) + n
+    InstructionFoldingCase<uint32_t>(
+        Header() + "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%n = OpVariable %_ptr_v2int Function\n" +
+            "%3 = OpLoad %v2int %n\n" +
+            "%2 = OpIAdd %v2int %v2int_0_0 %3\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd",
+        2, 3)
+));
+
 INSTANTIATE_TEST_CASE_P(ClampAndCmpLHS, GeneralInstructionFoldingTest,
 ::testing::Values(
     // Test case 0: Don't Fold 0.0 < clamp(-1, 1)
@@ -3785,6 +3873,36 @@ TEST_P(MatchingInstructionFoldingTest, Case) {
   }
 }
 
+INSTANTIATE_TEST_CASE_P(RedundantIntegerMatching, MatchingInstructionFoldingTest,
+::testing::Values(
+    // Test case 0: Fold 0 + n (change sign)
+    InstructionFoldingCase<bool>(
+        Header() +
+            "; CHECK: [[uint:%\\w+]] = OpTypeInt 32 0\n" +
+            "; CHECK: %2 = OpBitcast [[uint]] %3\n" +
+            "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%n = OpVariable %_ptr_int Function\n" +
+            "%3 = OpLoad %uint %n\n" +
+            "%2 = OpIAdd %uint %int_0 %3\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd\n",
+        2, true),
+    // Test case 0: Fold 0 + n (change sign)
+    InstructionFoldingCase<bool>(
+        Header() +
+            "; CHECK: [[int:%\\w+]] = OpTypeInt 32 1\n" +
+            "; CHECK: %2 = OpBitcast [[int]] %3\n" +
+            "%main = OpFunction %void None %void_func\n" +
+            "%main_lab = OpLabel\n" +
+            "%n = OpVariable %_ptr_int Function\n" +
+            "%3 = OpLoad %int %n\n" +
+            "%2 = OpIAdd %int %uint_0 %3\n" +
+            "OpReturn\n" +
+            "OpFunctionEnd\n",
+        2, true)
+));
+
 INSTANTIATE_TEST_CASE_P(MergeNegateTest, MatchingInstructionFoldingTest,
 ::testing::Values(
   // Test case 0: fold consecutive fnegate
diff --git a/tools/opt/opt.cpp b/tools/opt/opt.cpp
index 44047449..2fde5e8c 100644
--- a/tools/opt/opt.cpp
+++ b/tools/opt/opt.cpp
@@ -106,6 +106,9 @@ Options (in lexicographical order):
                Cleanup the control flow graph. This will remove any unnecessary
                code from the CFG like unreachable code. Performed on entry
                point call tree functions and exported functions.
+  --combine-access-chains
+               Combines chained access chains to produce a single instruction
+               where possible.
   --compact-ids
                Remap result ids to a compact range starting from %%1 and without
                any gaps.