Rename 'main' on some backends (#7105)

* Rename 'main' on some backednds

Fixes #5542

Some backends like cuda, metal, cpu do not allow 'main' as the entry
point. This commit adds a new warning that is emitted when a program
uses main as the entry point. In addition to emitting the warning, it
internally renames the entry point to "main_". It also adds a test to
check these for the three backends.

* format code

* move test to diagnostics

* rename test to diagnostic

* generate unique name

---------

Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

4 files changed, 40 insertions, 1 deletions

diff --git a/source/slang/slang-diagnostic-defs.h b/source/slang/slang-diagnostic-defs.h
index dbd4da588..808d867b6 100644
--- a/source/slang/slang-diagnostic-defs.h
+++ b/source/slang/slang-diagnostic-defs.h
@@ -2765,6 +2765,12 @@ DIAGNOSTIC(
     noBlocksOrIntrinsic,
     "no blocks found for function definition, is there a '$0' intrinsic missing?")
 
+DIAGNOSTIC(
+    40100,
+    Warning,
+    mainEntryPointRenamed,
+    "entry point '$0' is not allowed, and has been renamed to '$1'")
+
 //
 // Ray tracing
 //
diff --git a/source/slang/slang-emit-c-like.cpp b/source/slang/slang-emit-c-like.cpp
index 141a843f2..b2dc9b014 100644
--- a/source/slang/slang-emit-c-like.cpp
+++ b/source/slang/slang-emit-c-like.cpp
@@ -1109,9 +1109,25 @@ void CLikeSourceEmitter::appendScrubbedName(const UnownedStringSlice& name, Stri
     }
 }
 
+inline String CLikeSourceEmitter::maybeMakeEntryPointNameValid(String name, DiagnosticSink* sink)
+{
+    if (isCPUTarget(getTargetReq()) || isCUDATarget(getTargetReq()) ||
+        isMetalTarget(getTargetReq()))
+    {
+        if (name == "main")
+        {
+            String newName = _generateUniqueName(name.getUnownedSlice());
+            sink->diagnose(SourceLoc(), Diagnostics::mainEntryPointRenamed, name, newName);
+            return newName;
+        }
+    }
+    return name;
+}
+
 String CLikeSourceEmitter::generateEntryPointNameImpl(IREntryPointDecoration* entryPointDecor)
 {
-    return entryPointDecor->getName()->getStringSlice();
+    String name = entryPointDecor->getName()->getStringSlice();
+    return maybeMakeEntryPointNameValid(name, getSink());
 }
 
 String CLikeSourceEmitter::_generateUniqueName(const UnownedStringSlice& name)
diff --git a/source/slang/slang-emit-c-like.h b/source/slang/slang-emit-c-like.h
index f38158c0a..78793f655 100644
--- a/source/slang/slang-emit-c-like.h
+++ b/source/slang/slang-emit-c-like.h
@@ -739,6 +739,9 @@ protected:
 
     Dictionary<const char*, IRStringLit*> m_builtinPreludes;
 
+    // Rename entry point if target doesn't allow the name (e.g., 'main')
+    virtual String maybeMakeEntryPointNameValid(String name, DiagnosticSink* sink);
+
     // Indicates if we are emiting for DXC cooperative vector POC.
     bool isCoopvecPoc = false;
 };
diff --git a/tests/diagnostics/entry-point-main-warning.slang b/tests/diagnostics/entry-point-main-warning.slang
new file mode 100644
index 000000000..9d880dbb1
--- /dev/null
+++ b/tests/diagnostics/entry-point-main-warning.slang
@@ -0,0 +1,14 @@
+// Test to check if we emit a warning and rename main to main_ on CUDA, CPU, metal backends
+
+//DIAGNOSTIC_TEST:SIMPLE(filecheck=CHECK): -entry main -target cuda
+//DIAGNOSTIC_TEST:SIMPLE(filecheck=CHECK): -entry main -target metal
+//DIAGNOSTIC_TEST:SIMPLE(filecheck=CHECK): -entry main -target cpp
+[shader("compute")]
+[numthreads(1,1,1)]
+void main(RWBuffer<float> output)
+{
+    output[0] = 1.0f;
+}
+
+// CHECK: warning 40100: entry point 'main' is not allowed, and has been renamed to 'main_0'
+// CHECK: void main_
\ No newline at end of file