From a10a94dcb86e51d74d7c545d99d98110f88e3081 Mon Sep 17 00:00:00 2001
From: jsmall-nvidia <jsmall@nvidia.com>
Date: Tue, 16 Aug 2022 16:24:37 -0400
Subject: Add some simple macro defines including __HLSL_VERSION (#2363)

* #include an absolute path didn't work - because paths were taken to always be relative.

* Add standard macros including __HLSL_VERSION

* Added hlsl test.

* Defined standard macro names to values, so not undefined. Allows more convenient #if style.

Co-authored-by: Yong He <yonghe@outlook.com>
---
 source/slang/slang.cpp                             | 42 +++++++++++++++++++---
 tests/preprocessor/simple-pre-defined.hlsl         |  9 +++++
 .../preprocessor/simple-pre-defined.hlsl.expected  |  6 ++++
 tests/preprocessor/simple-pre-defined.slang        |  9 +++++
 .../preprocessor/simple-pre-defined.slang.expected |  6 ++++
 5 files changed, 68 insertions(+), 4 deletions(-)
 create mode 100644 tests/preprocessor/simple-pre-defined.hlsl
 create mode 100644 tests/preprocessor/simple-pre-defined.hlsl.expected
 create mode 100644 tests/preprocessor/simple-pre-defined.slang
 create mode 100644 tests/preprocessor/simple-pre-defined.slang.expected

diff --git a/source/slang/slang.cpp b/source/slang/slang.cpp
index 4f135d144..710cc0b45 100644
--- a/source/slang/slang.cpp
+++ b/source/slang/slang.cpp
@@ -1964,6 +1964,9 @@ void FrontEndCompileRequest::parseTranslationUnit(
         break;
     }
 
+    // TODO(JS):
+    // 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);
@@ -1972,12 +1975,45 @@ void FrontEndCompileRequest::parseTranslationUnit(
     for(auto& def : translationUnit->preprocessorDefinitions)
         combinedPreprocessorDefinitions.Add(def.Key, def.Value);
 
+    // Define standard macros, if not already defined. This style assumes using `#if __SOME_VAR` style, as in
+    // 
+    // ```
+    // #if __SLANG_COMPILER__
+    // ```
+    // 
+    // This choice is made because slang outputs a warning on using a variable in an #if if not defined
+    //
+    // Of course this means using #ifndef/#ifdef/defined() is probably not appropraite with thes variables.
+    {
+        // Used to identify level of HLSL language compatibility
+        combinedPreprocessorDefinitions.AddIfNotExists("__HLSL_VERSION", "2020");
+
+        // Indicates this is being compiled by the slang *compiler*
+        combinedPreprocessorDefinitions.AddIfNotExists("__SLANG_COMPILER__", "1");
+
+        // Set macro depending on source type
+        switch (translationUnit->sourceLanguage)
+        {
+            case SourceLanguage::HLSL:
+                // Used to indicate compiled as HLSL language
+                combinedPreprocessorDefinitions.AddIfNotExists("__HLSL__", "1");
+                break;
+            case SourceLanguage::Slang:
+                // Used to indicate compiled as Slang language
+                combinedPreprocessorDefinitions.AddIfNotExists("__SLANG__", "1");
+                break;
+            default: break;
+        }
+
+        // If not set, define as 0.
+        combinedPreprocessorDefinitions.AddIfNotExists("__HLSL__", "0");
+        combinedPreprocessorDefinitions.AddIfNotExists("__SLANG__", "0");
+    }
+
     auto module = translationUnit->getModule();
 
     ASTBuilder* astBuilder = module->getASTBuilder();
 
-    //ASTBuilder* astBuilder = linkage->getASTBuilder();
-
     ModuleDecl* translationUnitSyntax = astBuilder->create<ModuleDecl>();
 
     translationUnitSyntax->nameAndLoc.name = translationUnit->moduleName;
@@ -2060,8 +2096,6 @@ void FrontEndCompileRequest::parseTranslationUnit(
             }
         }
 
-
-
 #if 0
         // Test serialization
         {
diff --git a/tests/preprocessor/simple-pre-defined.hlsl b/tests/preprocessor/simple-pre-defined.hlsl
new file mode 100644
index 000000000..7789eb8eb
--- /dev/null
+++ b/tests/preprocessor/simple-pre-defined.hlsl
@@ -0,0 +1,9 @@
+//DIAGNOSTIC_TEST:SIMPLE:-E 
+
+__SLANG_COMPILER__
+
+__HLSL_VERSION
+
+__SLANG__
+
+__HLSL__
\ No newline at end of file
diff --git a/tests/preprocessor/simple-pre-defined.hlsl.expected b/tests/preprocessor/simple-pre-defined.hlsl.expected
new file mode 100644
index 000000000..98911f3c7
--- /dev/null
+++ b/tests/preprocessor/simple-pre-defined.hlsl.expected
@@ -0,0 +1,6 @@
+result code = 0
+standard error = {
+}
+standard output = {
+1 2020 0 1 
+}
diff --git a/tests/preprocessor/simple-pre-defined.slang b/tests/preprocessor/simple-pre-defined.slang
new file mode 100644
index 000000000..7789eb8eb
--- /dev/null
+++ b/tests/preprocessor/simple-pre-defined.slang
@@ -0,0 +1,9 @@
+//DIAGNOSTIC_TEST:SIMPLE:-E 
+
+__SLANG_COMPILER__
+
+__HLSL_VERSION
+
+__SLANG__
+
+__HLSL__
\ No newline at end of file
diff --git a/tests/preprocessor/simple-pre-defined.slang.expected b/tests/preprocessor/simple-pre-defined.slang.expected
new file mode 100644
index 000000000..4b5184e74
--- /dev/null
+++ b/tests/preprocessor/simple-pre-defined.slang.expected
@@ -0,0 +1,6 @@
+result code = 0
+standard error = {
+}
+standard output = {
+1 2020 1 0 
+}
-- 
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