utils: Add Lookup()

A find or return-default utility.
Rename `find_or_replace.h` to `map.h` which contains both these utilties that operate on maps.

Change-Id: Iaa76ea3f5c5a1210e413c131dd0556c126ee5d0a
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/70521
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

src/BUILD.gn

@@ -485,8 +485,8 @@ libtint_source_set("libtint_core_all_src") {
     "transform/zero_init_workgroup_memory.cc",
     "transform/zero_init_workgroup_memory.h",
     "utils/enum_set.h",
-    "utils/get_or_create.h",
     "utils/hash.h",
+    "utils/map.h",
     "utils/math.h",
     "utils/scoped_assignment.h",
     "utils/string.h",

src/CMakeLists.txt

@@ -397,8 +397,8 @@ set(TINT_LIB_SRCS
   sem/void_type.cc
   sem/void_type.h
   utils/enum_set.h
-  utils/get_or_create.h
   utils/hash.h
+  utils/map.h
   utils/math.h
   utils/scoped_assignment.h
   utils/string.h
@@ -730,10 +730,10 @@ if(${TINT_BUILD_TESTS})
     transform/transform_test.cc
     utils/defer_test.cc
     utils/enum_set_test.cc
-    utils/get_or_create_test.cc
     utils/hash_test.cc
     utils/io/command_test.cc
     utils/io/tmpfile_test.cc
+    utils/map_test.cc
     utils/math_test.cc
     utils/reverse_test.cc
     utils/scoped_assignment_test.cc

src/clone_context.cc

@@ -17,7 +17,7 @@
 #include <string>
 
 #include "src/program_builder.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 
 TINT_INSTANTIATE_TYPEINFO(tint::Cloneable);
 

src/intrinsic_table.cc

@@ -28,8 +28,8 @@
 #include "src/sem/pipeline_stage_set.h"
 #include "src/sem/sampled_texture_type.h"
 #include "src/sem/storage_texture_type.h"
-#include "src/utils/get_or_create.h"
 #include "src/utils/hash.h"
+#include "src/utils/map.h"
 #include "src/utils/math.h"
 #include "src/utils/scoped_assignment.h"
 

src/reader/spirv/parser_type.cc

@@ -19,7 +19,7 @@
 #include <utility>
 
 #include "src/program_builder.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 #include "src/utils/hash.h"
 
 TINT_INSTANTIATE_TYPEINFO(tint::reader::spirv::Type);

src/resolver/resolver.cc

@@ -74,7 +74,7 @@
 #include "src/sem/type_conversion.h"
 #include "src/sem/variable.h"
 #include "src/utils/defer.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 #include "src/utils/math.h"
 #include "src/utils/reverse.h"
 #include "src/utils/scoped_assignment.h"

src/resolver/resolver_constants.cc

@@ -16,7 +16,7 @@
 
 #include "src/sem/constant.h"
 #include "src/sem/type_constructor.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 
 namespace tint {
 namespace resolver {

src/resolver/resolver_validation.cc

@@ -74,7 +74,7 @@
 #include "src/sem/type_conversion.h"
 #include "src/sem/variable.h"
 #include "src/utils/defer.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 #include "src/utils/math.h"
 #include "src/utils/reverse.h"
 #include "src/utils/scoped_assignment.h"

src/transform/calculate_array_length.cc

@@ -25,7 +25,7 @@
 #include "src/sem/statement.h"
 #include "src/sem/struct.h"
 #include "src/sem/variable.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 #include "src/utils/hash.h"
 
 TINT_INSTANTIATE_TYPEINFO(tint::transform::CalculateArrayLength);

src/transform/decompose_memory_access.cc

@@ -35,7 +35,7 @@
 #include "src/sem/statement.h"
 #include "src/sem/struct.h"
 #include "src/sem/variable.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 #include "src/utils/hash.h"
 
 TINT_INSTANTIATE_TYPEINFO(tint::transform::DecomposeMemoryAccess);

src/transform/decompose_strided_matrix.cc

@@ -23,7 +23,7 @@
 #include "src/sem/member_accessor_expression.h"
 #include "src/transform/inline_pointer_lets.h"
 #include "src/transform/simplify.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 #include "src/utils/hash.h"
 
 TINT_INSTANTIATE_TYPEINFO(tint::transform::DecomposeStridedMatrix);

src/transform/pad_array_elements.cc

@@ -22,7 +22,7 @@
 #include "src/sem/call.h"
 #include "src/sem/expression.h"
 #include "src/sem/type_constructor.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 
 TINT_INSTANTIATE_TYPEINFO(tint::transform::PadArrayElements);
 

src/transform/remove_phonies.cc

@@ -25,7 +25,7 @@
 #include "src/sem/function.h"
 #include "src/sem/statement.h"
 #include "src/sem/variable.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 #include "src/utils/scoped_assignment.h"
 
 TINT_INSTANTIATE_TYPEINFO(tint::transform::RemovePhonies);

src/transform/vertex_pulling.cc

@@ -23,7 +23,7 @@
 #include "src/ast/variable_decl_statement.h"
 #include "src/program_builder.h"
 #include "src/sem/variable.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 #include "src/utils/math.h"
 
 TINT_INSTANTIATE_TYPEINFO(tint::transform::VertexPulling);

src/transform/wrap_arrays_in_structs.cc

@@ -21,7 +21,7 @@
 #include "src/sem/call.h"
 #include "src/sem/expression.h"
 #include "src/sem/type_constructor.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 #include "src/utils/transform.h"
 
 TINT_INSTANTIATE_TYPEINFO(tint::transform::WrapArraysInStructs);

src/transform/zero_init_workgroup_memory.cc

@@ -25,7 +25,7 @@
 #include "src/sem/atomic_type.h"
 #include "src/sem/function.h"
 #include "src/sem/variable.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 #include "src/utils/unique_vector.h"
 
 TINT_INSTANTIATE_TYPEINFO(tint::transform::ZeroInitWorkgroupMemory);

src/utils/map.h

@@ -12,14 +12,30 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#ifndef SRC_UTILS_GET_OR_CREATE_H_
-#define SRC_UTILS_GET_OR_CREATE_H_
+#ifndef SRC_UTILS_MAP_H_
+#define SRC_UTILS_MAP_H_
 
 #include <unordered_map>
 
 namespace tint {
 namespace utils {
 
+/// Lookup is a utility function for fetching a value from an unordered map if
+/// it exists, otherwise returning the `if_missing` argument.
+/// @param map the unordered_map
+/// @param key the map key of the item to query
+/// @param if_missing the value to return if the map does not contain the given
+/// key. Defaults to the zero-initializer for the value type.
+/// @return the map item value, or `if_missing` if the map does not contain the
+/// given key
+template <typename K, typename V, typename H, typename C, typename KV = K>
+V Lookup(std::unordered_map<K, V, H, C>& map,
+         const KV& key,
+         const KV& if_missing = {}) {
+  auto it = map.find(key);
+  return it != map.end() ? it->second : if_missing;
+}
+
 /// GetOrCreate is a utility function for lazily adding to an unordered map.
 /// If the map already contains the key `key` then this is returned, otherwise
 /// `create()` is called and the result is added to the map and is returned.
@@ -43,4 +59,4 @@ V GetOrCreate(std::unordered_map<K, V, H, C>& map,
 }  // namespace utils
 }  // namespace tint
 
-#endif  //  SRC_UTILS_GET_OR_CREATE_H_
+#endif  //  SRC_UTILS_MAP_H_

src/utils/map_test.cc

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 
 #include <unordered_map>
 
@@ -22,6 +22,15 @@ namespace tint {
 namespace utils {
 namespace {
 
+TEST(Lookup, Test) {
+  std::unordered_map<int, int> map;
+  map.emplace(10, 1);
+  EXPECT_EQ(Lookup(map, 10, 0), 1);    // exists, with if_missing
+  EXPECT_EQ(Lookup(map, 10), 1);       // exists, without if_missing
+  EXPECT_EQ(Lookup(map, 20, 50), 50);  // missing, with if_missing
+  EXPECT_EQ(Lookup(map, 20), 0);       // missing, without if_missing
+}
+
 TEST(GetOrCreateTest, NewKey) {
   std::unordered_map<int, int> map;
   EXPECT_EQ(GetOrCreate(map, 1, [&] { return 2; }), 2);

src/writer/glsl/generator_impl.cc

@@ -47,7 +47,7 @@
 #include "src/transform/calculate_array_length.h"
 #include "src/transform/glsl.h"
 #include "src/utils/defer.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 #include "src/utils/scoped_assignment.h"
 #include "src/writer/append_vector.h"
 #include "src/writer/float_to_string.h"

src/writer/hlsl/generator_impl.cc

@@ -61,7 +61,7 @@
 #include "src/transform/simplify.h"
 #include "src/transform/zero_init_workgroup_memory.h"
 #include "src/utils/defer.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 #include "src/utils/scoped_assignment.h"
 #include "src/writer/append_vector.h"
 #include "src/writer/float_to_string.h"

src/writer/msl/generator_impl.cc

@@ -71,7 +71,7 @@
 #include "src/transform/wrap_arrays_in_structs.h"
 #include "src/transform/zero_init_workgroup_memory.h"
 #include "src/utils/defer.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 #include "src/utils/scoped_assignment.h"
 #include "src/writer/float_to_string.h"
 

src/writer/spirv/builder.cc

@@ -51,7 +51,7 @@
 #include "src/transform/vectorize_scalar_matrix_constructors.h"
 #include "src/transform/zero_init_workgroup_memory.h"
 #include "src/utils/defer.h"
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 #include "src/writer/append_vector.h"
 
 namespace tint {

src/writer/text_generator.cc

@@ -17,7 +17,7 @@
 #include <algorithm>
 #include <limits>
 
-#include "src/utils/get_or_create.h"
+#include "src/utils/map.h"
 
 namespace tint {
 namespace writer {

test/BUILD.gn

@@ -339,10 +339,10 @@ tint_unittests_source_set("tint_unittests_utils_src") {
   sources = [
     "../src/utils/defer_test.cc",
     "../src/utils/enum_set_test.cc",
-    "../src/utils/get_or_create_test.cc",
     "../src/utils/hash_test.cc",
     "../src/utils/io/command_test.cc",
     "../src/utils/io/tmpfile_test.cc",
+    "../src/utils/map_test.cc",
     "../src/utils/math_test.cc",
     "../src/utils/reverse_test.cc",
     "../src/utils/scoped_assignment_test.cc",