Diagnostic on use of unsupported entry point modifiers (#8487)

Generate a diagnostic warning whenever unsupported modifiers (keywords,
attributes) are found on entry point parameters. These have been
silently ignored up until now, with the parser accepting them but Slang
not actually doing anything with them.

Fixes #7151

---------

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

3 files changed, 72 insertions, 0 deletions

diff --git a/source/slang/slang-check-shader.cpp b/source/slang/slang-check-shader.cpp
index 29134131c..ed62e948d 100644
--- a/source/slang/slang-check-shader.cpp
+++ b/source/slang/slang-check-shader.cpp
@@ -531,6 +531,50 @@ void validateEntryPoint(EntryPoint* entryPoint, DiagnosticSink* sink)
         }
     }
 
+    // Attribute and keyword diagnostics. Check for the [[vk::binding]] and [[vk::push_constants]]
+    // attributes, and the register() and packoffset() keywords on entry point parameters. Slang
+    // currently ignores these, which can lead to user confusion whenever the output does not
+    // correspond to what was requested. Conversely, Slang silently generating output that just
+    // happens to align with what's requested can also lead to user confusion, with the user
+    // mistakenly believing that the modifiers are working as intended.
+    //
+    // Note that this only checks when they're used on entry point parameters.
+    for (const auto& param : entryPointFuncDecl->getParameters())
+    {
+        if (param->findModifier<GLSLBindingAttribute>())
+        {
+            sink->diagnose(
+                param,
+                Diagnostics::unhandledModOnEntryPointParameter,
+                "attribute '[[vk::binding(...)]]'",
+                param->getName());
+        }
+        if (param->findModifier<PushConstantAttribute>())
+        {
+            sink->diagnose(
+                param,
+                Diagnostics::unhandledModOnEntryPointParameter,
+                "attribute '[[vk::push_constant]]'",
+                param->getName());
+        }
+        if (param->findModifier<HLSLRegisterSemantic>())
+        {
+            sink->diagnose(
+                param,
+                Diagnostics::unhandledModOnEntryPointParameter,
+                "keyword 'register'",
+                param->getName());
+        }
+        if (param->findModifier<HLSLPackOffsetSemantic>())
+        {
+            sink->diagnose(
+                param,
+                Diagnostics::unhandledModOnEntryPointParameter,
+                "keyword 'packoffset'",
+                param->getName());
+        }
+    }
+
     for (auto target : linkage->targets)
     {
         auto targetCaps = target->getTargetCaps();
diff --git a/source/slang/slang-diagnostic-defs.h b/source/slang/slang-diagnostic-defs.h
index 08e852547..6d9f7faab 100644
--- a/source/slang/slang-diagnostic-defs.h
+++ b/source/slang/slang-diagnostic-defs.h
@@ -2077,6 +2077,12 @@ DIAGNOSTIC(
     "expected a constant value of type '$0' as argument for specialization parameter '$1'")
 
 DIAGNOSTIC(
+    38010,
+    Warning,
+    unhandledModOnEntryPointParameter,
+    "$0 on parameter '$1' is unsupported on entry point parameters and will be ignored")
+
+DIAGNOSTIC(
     38100,
     Error,
     typeDoesntImplementInterfaceRequirement,
diff --git a/tests/diagnostics/entry-point-mod-errors.slang b/tests/diagnostics/entry-point-mod-errors.slang
new file mode 100644
index 000000000..090ce5e33
--- /dev/null
+++ b/tests/diagnostics/entry-point-mod-errors.slang
@@ -0,0 +1,22 @@
+// Test to check if we emit a warning when unhandled modifiers are applied to
+// entry point parameters.
+
+//DIAGNOSTIC_TEST:SIMPLE(filecheck=CHECK): -entry computeMain -target cuda
+//DIAGNOSTIC_TEST:SIMPLE(filecheck=CHECK): -entry computeMain -target metal
+//DIAGNOSTIC_TEST:SIMPLE(filecheck=CHECK): -entry computeMain -target cpp
+[shader("compute")]
+[numthreads(1,1,1)]
+void computeMain(
+// CHECK: ([[#@LINE+1]]): warning 38010: {{.*}}vk::binding
+    [[vk::binding(5, 4)]] RWStructuredBuffer<uint> test1,
+// CHECK: ([[#@LINE+1]]): warning 38010: {{.*}}vk::push_constant
+    [[vk::push_constant]] RWStructuredBuffer<float> test2,
+// CHECK: ([[#@LINE+1]]): warning 38010: {{.*}}register
+    RWStructuredBuffer<float> test3 : register(r0),
+// CHECK: ([[#@LINE+1]]): warning 38010: {{.*}}packoffset
+    float test4 : packoffset(c4),
+    RWBuffer<float> output
+)
+{
+    output[0] = test2[0];
+}