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, 3 insertions, 8 deletions

diff --git a/source/slang/slang-preprocessor.cpp b/source/slang/slang-preprocessor.cpp
index 4cc9bd113..aefbf7619 100644
--- a/source/slang/slang-preprocessor.cpp
+++ b/source/slang/slang-preprocessor.cpp
@@ -3864,11 +3864,8 @@ static Token ReadToken(Preprocessor* preprocessor)
 // clean up after an environment
 Environment::~Environment()
 {
-    for (auto pair : this->macros)
-    {
-        auto macro = pair.value;
+    for (const auto& [_, macro] : this->macros)
         delete macro;
-    }
 }
 
 // Add a simple macro definition from a string (e.g., for a
@@ -4066,10 +4063,8 @@ TokenList preprocessSource(
 
     if(desc.defines)
     {
-        for (auto p : *desc.defines)
-        {
-            DefineMacro(&preprocessor, p.key, p.value);
-        }
+        for (const auto& [key, value] : *desc.defines)
+            DefineMacro(&preprocessor, key, value);
     }
 
     {