diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index d0b678c..d603688 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -411,6 +411,7 @@
     writer/spirv/builder_entry_point_test.cc
     writer/spirv/builder_function_test.cc
     writer/spirv/builder_global_variable_test.cc
+    writer/spirv/builder_initializer_expression_test.cc
     writer/spirv/builder_literal_test.cc
     writer/spirv/builder_test.cc
     writer/spirv/builder_type_test.cc
diff --git a/src/ast/variable.h b/src/ast/variable.h
index 3fec0d6..752296d 100644
--- a/src/ast/variable.h
+++ b/src/ast/variable.h
@@ -79,6 +79,8 @@
   }
   /// @returns the initializer expression or nullptr if none set
   Expression* initializer() const { return initializer_.get(); }
+  /// @returns true if the variable has an initializer
+  bool has_initializer() const { return initializer_ != nullptr; }
 
   /// Sets if the variable is constant
   /// @param val the value to be set
diff --git a/src/writer/spirv/builder.cc b/src/writer/spirv/builder.cc
index 7896ae0..9e1b9b8 100644
--- a/src/writer/spirv/builder.cc
+++ b/src/writer/spirv/builder.cc
@@ -13,14 +13,17 @@
 
 #include "src/writer/spirv/builder.h"
 
+#include <sstream>
 #include <utility>
 
 #include "spirv/unified1/spirv.h"
 #include "src/ast/binding_decoration.h"
 #include "src/ast/bool_literal.h"
 #include "src/ast/builtin_decoration.h"
+#include "src/ast/const_initializer_expression.h"
 #include "src/ast/decorated_variable.h"
 #include "src/ast/float_literal.h"
+#include "src/ast/initializer_expression.h"
 #include "src/ast/int_literal.h"
 #include "src/ast/location_decoration.h"
 #include "src/ast/set_decoration.h"
@@ -33,6 +36,7 @@
 #include "src/ast/type/struct_type.h"
 #include "src/ast/type/u32_type.h"
 #include "src/ast/type/vector_type.h"
+#include "src/ast/type_initializer_expression.h"
 #include "src/ast/uint_literal.h"
 
 namespace tint {
@@ -167,6 +171,15 @@
   return true;
 }
 
+uint32_t Builder::GenerateExpression(ast::Expression* expr) {
+  if (expr->IsInitializer()) {
+    return GenerateInitializerExpression(expr->AsInitializer(), false);
+  }
+
+  error_ = "unknown expression type";
+  return 0;
+}
+
 bool Builder::GenerateFunction(ast::Function* func) {
   uint32_t func_type_id = GenerateFunctionTypeIfNeeded(func);
   if (func_type_id == 0) {
@@ -220,14 +233,33 @@
 }
 
 bool Builder::GenerateGlobalVariable(ast::Variable* var) {
-  auto result = result_op();
-  auto var_id = result.to_i();
+  uint32_t init_id = 0;
+  if (var->has_initializer()) {
+    if (!var->initializer()->IsInitializer()) {
+      error_ = "constant initializer expected";
+      return false;
+    }
+
+    init_id = GenerateInitializerExpression(var->initializer()->AsInitializer(),
+                                            true);
+    if (init_id == 0) {
+      return false;
+    }
+  }
 
   if (var->is_const()) {
-    // TODO(dsinclair): Handle const variables
-    return false;
+    if (!var->has_initializer()) {
+      error_ = "missing initializer for constant";
+      return false;
+    }
+
+    // TODO(dsinclair): Store variable name to id
+    return true;
   }
 
+  auto result = result_op();
+  auto var_id = result.to_i();
+
   auto sc = var->storage_class() == ast::StorageClass::kNone
                 ? ast::StorageClass::kPrivate
                 : var->storage_class();
@@ -238,11 +270,16 @@
     return false;
   }
 
-  // TODO(dsinclair): Handle variable initializer
   push_debug(spv::Op::OpName,
              {Operand::Int(var_id), Operand::String(var->name())});
-  push_type(spv::Op::OpVariable, {Operand::Int(type_id), result,
-                                  Operand::Int(ConvertStorageClass(sc))});
+
+  std::vector<Operand> ops = {Operand::Int(type_id), result,
+                              Operand::Int(ConvertStorageClass(sc))};
+  if (var->has_initializer()) {
+    ops.push_back(Operand::Int(init_id));
+  }
+
+  push_type(spv::Op::OpVariable, std::move(ops));
 
   if (var->IsDecorated()) {
     for (const auto& deco : var->AsDecorated()->decorations()) {
@@ -270,6 +307,8 @@
     }
   }
 
+  // TODO(dsinclair) Mapping of variable name to id
+
   return true;
 }
 
@@ -283,6 +322,58 @@
   import_name_to_id_[imp->name()] = id;
 }
 
+uint32_t Builder::GenerateInitializerExpression(
+    ast::InitializerExpression* expr,
+    bool is_global_init) {
+  if (expr->IsConstInitializer()) {
+    return GenerateLiteralIfNeeded(expr->AsConstInitializer()->literal());
+  }
+  if (expr->IsTypeInitializer()) {
+    auto init = expr->AsTypeInitializer();
+    auto type_id = GenerateTypeIfNeeded(init->type());
+    if (type_id == 0) {
+      return 0;
+    }
+
+    std::ostringstream out;
+    out << "__const";
+
+    std::vector<Operand> ops;
+    for (const auto& e : init->values()) {
+      if (is_global_init && !e->IsInitializer()) {
+        error_ = "initializer must be a constant expression";
+        return 0;
+      }
+      auto id =
+          GenerateInitializerExpression(e->AsInitializer(), is_global_init);
+      if (id == 0) {
+        return 0;
+      }
+
+      out << "_" << id;
+      ops.push_back(Operand::Int(id));
+    }
+
+    auto str = out.str();
+    auto val = const_to_id_.find(str);
+    if (val != const_to_id_.end()) {
+      return val->second;
+    }
+
+    auto result = result_op();
+    ops.insert(ops.begin(), result);
+    ops.insert(ops.begin(), Operand::Int(type_id));
+
+    const_to_id_[str] = result.to_i();
+
+    push_type(spv::Op::OpCompositeConstruct, ops);
+    return result.to_i();
+  }
+
+  error_ = "unknown initializer expression";
+  return 0;
+}
+
 uint32_t Builder::GenerateLiteralIfNeeded(ast::Literal* lit) {
   auto type_id = GenerateTypeIfNeeded(lit->type());
   if (type_id == 0) {
diff --git a/src/writer/spirv/builder.h b/src/writer/spirv/builder.h
index 6c4437e..5490b16 100644
--- a/src/writer/spirv/builder.h
+++ b/src/writer/spirv/builder.h
@@ -137,6 +137,10 @@
   /// @param ep the entry point
   /// @returns true if the instruction was generated, false otherwise
   bool GenerateEntryPoint(ast::EntryPoint* ep);
+  /// Generates an expression
+  /// @param expr the expression to generate
+  /// @returns the resulting ID of the expression or 0 on error
+  uint32_t GenerateExpression(ast::Expression* expr);
   /// Generates the instructions for a function
   /// @param func the function to generate
   /// @returns true if the instructions were generated
@@ -152,6 +156,12 @@
   /// Generates an import instruction
   /// @param imp the import
   void GenerateImport(ast::Import* imp);
+  /// Generates an initializer expression
+  /// @param expr the expression to generate
+  /// @param is_global_init set true if this is a global variable initializer
+  /// @returns the ID of the expression or 0 on failure.
+  uint32_t GenerateInitializerExpression(ast::InitializerExpression* expr,
+                                         bool is_global_init);
   /// Generates a literal constant if needed
   /// @param lit the literal to generate
   /// @returns the ID on success or 0 on failure
diff --git a/src/writer/spirv/builder_global_variable_test.cc b/src/writer/spirv/builder_global_variable_test.cc
index 693ea93..0a66899 100644
--- a/src/writer/spirv/builder_global_variable_test.cc
+++ b/src/writer/spirv/builder_global_variable_test.cc
@@ -18,11 +18,15 @@
 #include "src/ast/binding_decoration.h"
 #include "src/ast/builtin.h"
 #include "src/ast/builtin_decoration.h"
+#include "src/ast/const_initializer_expression.h"
 #include "src/ast/decorated_variable.h"
+#include "src/ast/float_literal.h"
 #include "src/ast/location_decoration.h"
 #include "src/ast/set_decoration.h"
 #include "src/ast/storage_class.h"
 #include "src/ast/type/f32_type.h"
+#include "src/ast/type/vector_type.h"
+#include "src/ast/type_initializer_expression.h"
 #include "src/ast/variable.h"
 #include "src/ast/variable_decoration.h"
 #include "src/writer/spirv/builder.h"
@@ -63,9 +67,70 @@
 )");
 }
 
-TEST_F(BuilderTest, DISABLED_GlobalVar_WithInitializer) {}
+TEST_F(BuilderTest, GlobalVar_WithInitializer) {
+  ast::type::F32Type f32;
+  ast::type::VectorType vec(&f32, 3);
 
-TEST_F(BuilderTest, DISABLED_GlobalVar_Const) {}
+  std::vector<std::unique_ptr<ast::Expression>> vals;
+  vals.push_back(std::make_unique<ast::ConstInitializerExpression>(
+      std::make_unique<ast::FloatLiteral>(&f32, 1.0f)));
+  vals.push_back(std::make_unique<ast::ConstInitializerExpression>(
+      std::make_unique<ast::FloatLiteral>(&f32, 1.0f)));
+  vals.push_back(std::make_unique<ast::ConstInitializerExpression>(
+      std::make_unique<ast::FloatLiteral>(&f32, 3.0f)));
+
+  auto init =
+      std::make_unique<ast::TypeInitializerExpression>(&vec, std::move(vals));
+
+  ast::Variable v("var", ast::StorageClass::kOutput, &f32);
+  v.set_initializer(std::move(init));
+
+  Builder b;
+  EXPECT_TRUE(b.GenerateGlobalVariable(&v)) << b.error();
+  ASSERT_FALSE(b.has_error()) << b.error();
+
+  EXPECT_EQ(DumpInstructions(b.debug()), R"(OpName %6 "var"
+)");
+  EXPECT_EQ(DumpInstructions(b.types()), R"(%2 = OpTypeFloat 32
+%1 = OpTypeVector %2 3
+%3 = OpConstant %2 1
+%4 = OpConstant %2 3
+%5 = OpCompositeConstruct %1 %3 %3 %4
+%7 = OpTypePointer Output %2
+%6 = OpVariable %7 Output %5
+)");
+}
+
+TEST_F(BuilderTest, GlobalVar_Const) {
+  ast::type::F32Type f32;
+  ast::type::VectorType vec(&f32, 3);
+
+  std::vector<std::unique_ptr<ast::Expression>> vals;
+  vals.push_back(std::make_unique<ast::ConstInitializerExpression>(
+      std::make_unique<ast::FloatLiteral>(&f32, 1.0f)));
+  vals.push_back(std::make_unique<ast::ConstInitializerExpression>(
+      std::make_unique<ast::FloatLiteral>(&f32, 1.0f)));
+  vals.push_back(std::make_unique<ast::ConstInitializerExpression>(
+      std::make_unique<ast::FloatLiteral>(&f32, 3.0f)));
+
+  auto init =
+      std::make_unique<ast::TypeInitializerExpression>(&vec, std::move(vals));
+
+  ast::Variable v("var", ast::StorageClass::kOutput, &f32);
+  v.set_initializer(std::move(init));
+  v.set_is_const(true);
+
+  Builder b;
+  EXPECT_TRUE(b.GenerateGlobalVariable(&v)) << b.error();
+  ASSERT_FALSE(b.has_error()) << b.error();
+
+  EXPECT_EQ(DumpInstructions(b.types()), R"(%2 = OpTypeFloat 32
+%1 = OpTypeVector %2 3
+%3 = OpConstant %2 1
+%4 = OpConstant %2 3
+%5 = OpCompositeConstruct %1 %3 %3 %4
+)");
+}
 
 TEST_F(BuilderTest, GlobalVar_WithLocation) {
   ast::type::F32Type f32;
diff --git a/src/writer/spirv/builder_initializer_expression_test.cc b/src/writer/spirv/builder_initializer_expression_test.cc
new file mode 100644
index 0000000..443493f
--- /dev/null
+++ b/src/writer/spirv/builder_initializer_expression_test.cc
@@ -0,0 +1,122 @@
+// Copyright 2020 The Tint Authors.
+//
+// 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 <string>
+
+#include "gtest/gtest.h"
+#include "spirv/unified1/spirv.h"
+#include "spirv/unified1/spirv.hpp11"
+#include "src/ast/const_initializer_expression.h"
+#include "src/ast/float_literal.h"
+#include "src/ast/relational_expression.h"
+#include "src/ast/type/f32_type.h"
+#include "src/ast/type/vector_type.h"
+#include "src/ast/type_initializer_expression.h"
+#include "src/writer/spirv/builder.h"
+#include "src/writer/spirv/spv_dump.h"
+
+namespace tint {
+namespace writer {
+namespace spirv {
+namespace {
+
+using BuilderTest = testing::Test;
+
+TEST_F(BuilderTest, Initializer_Const) {
+  ast::type::F32Type f32;
+  auto fl = std::make_unique<ast::FloatLiteral>(&f32, 42.2f);
+  ast::ConstInitializerExpression c(std::move(fl));
+
+  Builder b;
+  EXPECT_EQ(b.GenerateInitializerExpression(&c, true), 2);
+  ASSERT_FALSE(b.has_error()) << b.error();
+
+  EXPECT_EQ(DumpInstructions(b.types()), R"(%1 = OpTypeFloat 32
+%2 = OpConstant %1 42.2000008
+)");
+}
+
+TEST_F(BuilderTest, Initializer_Type) {
+  ast::type::F32Type f32;
+  ast::type::VectorType vec(&f32, 3);
+
+  std::vector<std::unique_ptr<ast::Expression>> vals;
+  vals.push_back(std::make_unique<ast::ConstInitializerExpression>(
+      std::make_unique<ast::FloatLiteral>(&f32, 1.0f)));
+  vals.push_back(std::make_unique<ast::ConstInitializerExpression>(
+      std::make_unique<ast::FloatLiteral>(&f32, 1.0f)));
+  vals.push_back(std::make_unique<ast::ConstInitializerExpression>(
+      std::make_unique<ast::FloatLiteral>(&f32, 3.0f)));
+
+  ast::TypeInitializerExpression t(&vec, std::move(vals));
+
+  Builder b;
+  EXPECT_EQ(b.GenerateInitializerExpression(&t, true), 5);
+  ASSERT_FALSE(b.has_error()) << b.error();
+
+  EXPECT_EQ(DumpInstructions(b.types()), R"(%2 = OpTypeFloat 32
+%1 = OpTypeVector %2 3
+%3 = OpConstant %2 1
+%4 = OpConstant %2 3
+%5 = OpCompositeConstruct %1 %3 %3 %4
+)");
+}
+
+TEST_F(BuilderTest, Initializer_Type_Dedups) {
+  ast::type::F32Type f32;
+  ast::type::VectorType vec(&f32, 3);
+
+  std::vector<std::unique_ptr<ast::Expression>> vals;
+  vals.push_back(std::make_unique<ast::ConstInitializerExpression>(
+      std::make_unique<ast::FloatLiteral>(&f32, 1.0f)));
+  vals.push_back(std::make_unique<ast::ConstInitializerExpression>(
+      std::make_unique<ast::FloatLiteral>(&f32, 1.0f)));
+  vals.push_back(std::make_unique<ast::ConstInitializerExpression>(
+      std::make_unique<ast::FloatLiteral>(&f32, 3.0f)));
+
+  ast::TypeInitializerExpression t(&vec, std::move(vals));
+
+  Builder b;
+  EXPECT_EQ(b.GenerateInitializerExpression(&t, true), 5);
+  EXPECT_EQ(b.GenerateInitializerExpression(&t, true), 5);
+  ASSERT_FALSE(b.has_error()) << b.error();
+}
+
+TEST_F(BuilderTest, Initializer_NonConst_Type_Fails) {
+  ast::type::F32Type f32;
+  ast::type::VectorType vec(&f32, 2);
+  auto rel = std::make_unique<ast::RelationalExpression>(
+      ast::Relation::kAdd,
+      std::make_unique<ast::ConstInitializerExpression>(
+          std::make_unique<ast::FloatLiteral>(&f32, 3.0f)),
+      std::make_unique<ast::ConstInitializerExpression>(
+          std::make_unique<ast::FloatLiteral>(&f32, 3.0f)));
+
+  std::vector<std::unique_ptr<ast::Expression>> vals;
+  vals.push_back(std::make_unique<ast::ConstInitializerExpression>(
+      std::make_unique<ast::FloatLiteral>(&f32, 1.0f)));
+  vals.push_back(std::move(rel));
+
+  ast::TypeInitializerExpression t(&vec, std::move(vals));
+
+  Builder b;
+  EXPECT_EQ(b.GenerateInitializerExpression(&t, true), 0);
+  EXPECT_TRUE(b.has_error());
+  EXPECT_EQ(b.error(), R"(initializer must be a constant expression)");
+}
+
+}  // namespace
+}  // namespace spirv
+}  // namespace writer
+}  // namespace tint
diff --git a/src/writer/spirv/operand.h b/src/writer/spirv/operand.h
index 161f263..de66a22 100644
--- a/src/writer/spirv/operand.h
+++ b/src/writer/spirv/operand.h
@@ -49,6 +49,9 @@
   Operand(const Operand&) = default;
   ~Operand();
 
+  /// Copy assignment
+  Operand& operator=(const Operand&) = default;
+
   /// Sets the float value
   /// @param val the value to set
   void set_float(float val) { float_val_ = val; }