Use ankerl/unordered_dense as a hashmap implementation (#3036)

* Correct namespace for getClockFrequency

* missing const

* Add missing assignment operator

* Remove unused variables

* Return correct modified variable

* Use stable hash code for file system identity

* terse static_assert

* Structured binding for map iteration

* Make (==) and getHashCode const on many structs

* Add ConstIterator for LinkedList

* Replace uses of ItemProxy::getValue with Dictionary::at

* Extract list of loads from gradientsMap before updating it

* Const correctness in type layout

* Add unordered_dense hashmap submodule

* Use wyhash or getHashCode in slang-hash.h

* refactor slang-hash.h

* Use ankerl/unordered_dense as a hashmap implementation

Notable changes:
- The subscript operator returns a reference directly to the value,
  rather than a lazy ItemProxy (pair of dict pointer and key)

slang-profile time (95% over 10 runs):

- Before: 6.3913906 (±0.0746)
- After:  5.9276123 (±0.0964)

* 64 bit hash for strings

So they have the same hash as char buffers with the same contents

* Narrowing warnings for gcc to match msvc

* revert back to c++17

* Correct c++ version for msvc

* Use path to unordered_dense which keeps tests happy

* Do not assign to and read from map in same expression

* Remove redundant map operations in primal-hoist

* Split out stable hash functions into slang-stable-hash.h

* 64 bit hash by default

* regenerate vs projects

* Correct return type from HashSetBase::getCount()

* correct width for call to Dictionary::reserve

* Use stable hash for obfuscated module ids

* Signed int for reserve

* clearer variable naming

* Parameterize Dictionary on hash and equality functors

* Allow heterogenous lookup for Dictionary

* missing const

* Use set over operator[] in some places

* Remove unused function

* s/at/getValue

1 files changed, 14 insertions, 19 deletions

diff --git a/source/slang/slang.cpp b/source/slang/slang.cpp
index 1edf62a38..71c705246 100644
--- a/source/slang/slang.cpp
+++ b/source/slang/slang.cpp
@@ -407,11 +407,8 @@ SlangResult Session::saveStdLib(SlangArchiveType archiveType, ISlangBlob** outBl
 
     SLANG_AST_BUILDER_RAII(m_builtinLinkage->getASTBuilder());
 
-    for (auto& pair : m_builtinLinkage->mapNameToLoadedModules)
+    for (const auto& [moduleName, module] : m_builtinLinkage->mapNameToLoadedModules)
     {
-        const Name* moduleName = pair.key;
-        Module* module = pair.value;
-
         // Set up options
         SerialContainerUtil::WriteOptions options;
 
@@ -943,10 +940,8 @@ Linkage::Linkage(Session* session, ASTBuilder* astBuilder, Linkage* builtinLinka
     // Copy of the built in linkages modules
     if (builtinLinkage)
     {
-        for (const auto& pair : builtinLinkage->mapNameToLoadedModules)
-        {
-            mapNameToLoadedModules.add(pair.key, pair.value);
-        }
+        for (const auto& nameToMod : builtinLinkage->mapNameToLoadedModules)
+            mapNameToLoadedModules.add(nameToMod);
     }
 
     {
@@ -1387,10 +1382,10 @@ void Linkage::buildHash(DigestBuilder<SHA1>& builder, SlangInt targetIndex)
     }
 
     // Add the preprocessor definitions to the hash
-    for (auto& key : preprocessorDefinitions)
+    for (const auto& [defName, defVal] : preprocessorDefinitions)
     {
-        builder.append(key.key);
-        builder.append(key.value);
+        builder.append(defName);
+        builder.append(defVal);
     }
 
     // Add the target specified by targetIndex
@@ -2074,9 +2069,9 @@ static void _calcViewInitiatingHierarchy(SourceManager* sourceManager, ViewIniti
     // Order all the children, by their raw SourceLocs. This is desirable, so that a trivial traversal
     // will traverse children in the order they are initiated in the parent source.
     // This assumes they increase in SourceLoc implies an later within a source file - this is true currently.
-    for (auto& pair : outHierarchy)
+    for (auto& [_, value] : outHierarchy)
     {
-        pair.value.sort([](SourceView* a, SourceView* b) -> bool { return a->getInitiatingSourceLoc().getRaw() < b->getInitiatingSourceLoc().getRaw(); });
+        value.sort([](SourceView* a, SourceView* b) -> bool { return a->getInitiatingSourceLoc().getRaw() < b->getInitiatingSourceLoc().getRaw(); });
     }
 }
 
@@ -2233,12 +2228,12 @@ void FrontEndCompileRequest::parseTranslationUnit(
     // Note! that a adding a define twice will cause an exception in debug builds
     // that may be desirable or not...
     Dictionary<String, String> combinedPreprocessorDefinitions;
-    for(auto& def : getLinkage()->preprocessorDefinitions)
-        combinedPreprocessorDefinitions.add(def.key, def.value);
-    for(auto& def : preprocessorDefinitions)
-        combinedPreprocessorDefinitions.add(def.key, def.value);
-    for(auto& def : translationUnit->preprocessorDefinitions)
-        combinedPreprocessorDefinitions.add(def.key, def.value);
+    for(const auto& def : getLinkage()->preprocessorDefinitions)
+        combinedPreprocessorDefinitions.add(def);
+    for(const auto& def : preprocessorDefinitions)
+        combinedPreprocessorDefinitions.add(def);
+    for(const auto& def : translationUnit->preprocessorDefinitions)
+        combinedPreprocessorDefinitions.add(def);
 
     // Define standard macros, if not already defined. This style assumes using `#if __SOME_VAR` style, as in
     //