From 844d8d2212d11f3d28a55c81f234c99db2c26250 Mon Sep 17 00:00:00 2001
From: Darren Wihandi <65404740+fairywreath@users.noreply.github.com>
Date: Fri, 21 Mar 2025 11:52:28 -0400
Subject: Emit errors for missing returns on unsupported targets (#6633)

* initial wip

* more WIP

* preserve old lower behavior

* remove unnecessary includes

* add test

* add no target case in test

* fix broken test

---------

Co-authored-by: Ellie Hermaszewska <ellieh@nvidia.com>
---
 source/slang/slang-ir-missing-return.cpp | 54 +++++++++++++++++++++++++++++---
 1 file changed, 49 insertions(+), 5 deletions(-)

(limited to 'source/slang/slang-ir-missing-return.cpp')

diff --git a/source/slang/slang-ir-missing-return.cpp b/source/slang/slang-ir-missing-return.cpp
index 9dcda37ca..82d1171e0 100644
--- a/source/slang/slang-ir-missing-return.cpp
+++ b/source/slang/slang-ir-missing-return.cpp
@@ -1,6 +1,8 @@
 // ir-missing-return.cpp
 #include "slang-ir-missing-return.h"
 
+#include "core/slang-type-text-util.h"
+#include "slang-compiler.h"
 #include "slang-ir-insts.h"
 #include "slang-ir.h"
 
@@ -10,7 +12,45 @@ namespace Slang
 class DiagnosticSink;
 struct IRModule;
 
-void checkForMissingReturnsRec(IRInst* inst, DiagnosticSink* sink)
+// Returns false if compilation target does not allow and errors out(i.e. during downstream
+// compilation) on missing returns.
+static bool doesTargetAllowMissingReturns(CodeGenTarget target)
+{
+    if (isKhronosTarget(target) || isWGPUTarget(target))
+    {
+        return false;
+    }
+
+    return true;
+}
+
+static void diagnoseMissingReturnForTarget(
+    IRMissingReturn* missingReturn,
+    DiagnosticSink* sink,
+    CodeGenTarget target,
+    bool diagnoseWarning)
+{
+    if (doesTargetAllowMissingReturns(target))
+    {
+        if (diagnoseWarning)
+        {
+            sink->diagnose(missingReturn, Diagnostics::missingReturn);
+        }
+    }
+    else
+    {
+        sink->diagnose(
+            missingReturn,
+            Diagnostics::missingReturnError,
+            TypeTextUtil::getCompileTargetName(SlangCompileTarget(target)));
+    }
+}
+
+void checkForMissingReturnsRec(
+    IRInst* inst,
+    DiagnosticSink* sink,
+    CodeGenTarget target,
+    bool diagnoseWarning)
 {
     if (auto code = as<IRGlobalValueWithCode>(inst))
     {
@@ -20,21 +60,25 @@ void checkForMissingReturnsRec(IRInst* inst, DiagnosticSink* sink)
 
             if (auto missingReturn = as<IRMissingReturn>(terminator))
             {
-                sink->diagnose(missingReturn, Diagnostics::missingReturn);
+                diagnoseMissingReturnForTarget(missingReturn, sink, target, diagnoseWarning);
             }
         }
     }
 
     for (auto childInst : inst->getDecorationsAndChildren())
     {
-        checkForMissingReturnsRec(childInst, sink);
+        checkForMissingReturnsRec(childInst, sink, target, diagnoseWarning);
     }
 }
 
-void checkForMissingReturns(IRModule* module, DiagnosticSink* sink)
+void checkForMissingReturns(
+    IRModule* module,
+    DiagnosticSink* sink,
+    CodeGenTarget target,
+    bool diagnoseWarning)
 {
     // Look for any `missingReturn` instructions
-    checkForMissingReturnsRec(module->getModuleInst(), sink);
+    checkForMissingReturnsRec(module->getModuleInst(), sink, target, diagnoseWarning);
 }
 
 } // namespace Slang
-- 
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