Add reader::spv::Namer::FindUnusedDerivedName

Bug: tint:3
Change-Id: I0a0e5646d7bcdc89fdaaf8b956dd61ed6148c7e9
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/17421
Reviewed-by: dan sinclair <dsinclair@google.com>

src/reader/spirv/namer.cc

@@ -15,6 +15,7 @@
 #include "src/reader/spirv/namer.h"
 
 #include <algorithm>
+#include <sstream>
 
 namespace tint {
 namespace reader {
@@ -48,12 +49,30 @@ std::string Namer::Sanitize(const std::string& suggested_name) {
   return result;
 }
 
+std::string Namer::FindUnusedDerivedName(const std::string& base_name) const {
+  // Ensure uniqueness among names.
+  std::string derived_name;
+  for (int i = 0;; i++) {
+    std::stringstream new_name_stream;
+    new_name_stream << base_name;
+    if (i > 0) {
+      new_name_stream << "_" << i;
+    }
+    derived_name = new_name_stream.str();
+    if (name_to_id_.count(derived_name) == 0) {
+      break;
+    }
+  }
+  return derived_name;
+}
+
 bool Namer::SaveName(uint32_t id, const std::string& name) {
   if (HasName(id)) {
     return Fail() << "internal error: ID " << id
                   << " already has registered name: " << id_to_name_[id];
   }
   id_to_name_[id] = name;
+  name_to_id_[name] = id;
   return true;
 }
 

src/reader/spirv/namer.h

@@ -63,6 +63,11 @@ class Namer {
     return id_to_name_.find(id)->second;
   }
 
+  /// Returns an unregistered name based on a given base name.
+  /// @param base_name the base name
+  /// @returns a new name
+  std::string FindUnusedDerivedName(const std::string& base_name) const;
+
   /// Records a mapping from the given ID to a name. Emits a failure
   /// if the ID already has a registered name.
   /// @param id the SPIR-V ID
@@ -75,6 +80,8 @@ class Namer {
 
   // Maps an ID to its registered name.
   std::unordered_map<uint32_t, std::string> id_to_name_;
+  // Maps a name to a SPIR-V ID, or 0 (the case for derived names).
+  std::unordered_map<std::string, uint32_t> name_to_id_;
 };
 
 }  // namespace spirv

src/reader/spirv/namer_test.cc

@@ -83,6 +83,26 @@ TEST_F(SpvNamerTest, NoNameRecorded) {
   EXPECT_TRUE(error().empty());
 }
 
+TEST_F(SpvNamerTest, FindUnusedDerivedName_NoRecordedName) {
+  Namer namer(fail_stream_);
+  EXPECT_THAT(namer.FindUnusedDerivedName("eleanor"), Eq("eleanor"));
+}
+
+TEST_F(SpvNamerTest, FindUnusedDerivedName_HasRecordedName) {
+  Namer namer(fail_stream_);
+  namer.SaveName(12, "rigby");
+  EXPECT_THAT(namer.FindUnusedDerivedName("rigby"), Eq("rigby_1"));
+}
+
+TEST_F(SpvNamerTest, FindUnusedDerivedName_HasMultipleConflicts) {
+  Namer namer(fail_stream_);
+  namer.SaveName(12, "rigby");
+  namer.SaveName(13, "rigby_1");
+  namer.SaveName(14, "rigby_3");
+  // It picks the first non-conflicting suffix.
+  EXPECT_THAT(namer.FindUnusedDerivedName("rigby"), Eq("rigby_2"));
+}
+
 TEST_F(SpvNamerTest, SaveNameOnce) {
   Namer namer(fail_stream_);