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

2 files changed, 5 insertions, 3 deletions

diff --git a/source/compiler-core/slang-source-loc.cpp b/source/compiler-core/slang-source-loc.cpp
index f9014e0d8..33f93074e 100644
--- a/source/compiler-core/slang-source-loc.cpp
+++ b/source/compiler-core/slang-source-loc.cpp
@@ -318,7 +318,6 @@ SlangResult SourceView::_findSourceMapLoc(SourceLoc loc, SourceLocType type, Han
     // view, which may be a parent to the current one. 
     auto lookupSourceManager = m_sourceFile->getSourceManager();
 
-    HandleSourceLoc handleLoc;
     SLANG_RETURN_ON_FAIL(_findLocWithSourceMap(lookupSourceManager, this, loc, type, outLoc));
 
     return SLANG_OK;
diff --git a/source/compiler-core/slang-visual-studio-compiler-util.cpp b/source/compiler-core/slang-visual-studio-compiler-util.cpp
index 81e00d73e..14fad0aec 100644
--- a/source/compiler-core/slang-visual-studio-compiler-util.cpp
+++ b/source/compiler-core/slang-visual-studio-compiler-util.cpp
@@ -83,14 +83,17 @@ static void _addFile(const String& path, const ArtifactDesc& desc, IOSFileArtifa
     // Display full path of source files in diagnostics
     cmdLine.addArg("/FC");
 
-    if (options.flags & CompileOptions::Flag::EnableExceptionHandling)
+    if (options.sourceLanguage == SLANG_SOURCE_LANGUAGE_CPP)
     {
-        if (options.sourceLanguage == SLANG_SOURCE_LANGUAGE_CPP)
+        if (options.flags & CompileOptions::Flag::EnableExceptionHandling)
         {
             // https://docs.microsoft.com/en-us/cpp/build/reference/eh-exception-handling-model?view=vs-2019
             // Assumes c functions cannot throw
             cmdLine.addArg("/EHsc");
         }
+
+        // To maintain parity with the slang compiler headers which are shared
+        cmdLine.addArg("/std:c++17");
     }
 
     if (options.flags & CompileOptions::Flag::Verbose)