Fix debug info generation for let variables in SPIR-V output (#7743)

* Initial plan

* Fix debug info for let variables

Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>

* Fix parameter count for emitDebugVar function call

Fixed regression where let variable debug info generation was missing the optional argIndex parameter in emitDebugVar call.

Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>

* Add location validity check for debug info generation

Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>

* Don't insert debug value for nondebuggable types.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>
Co-authored-by: Yong He <yonghe@outlook.com>

1 files changed, 42 insertions, 1 deletions

diff --git a/source/slang/slang-lower-to-ir.cpp b/source/slang/slang-lower-to-ir.cpp
index ab9f85b21..526e2f952 100644
--- a/source/slang/slang-lower-to-ir.cpp
+++ b/source/slang/slang-lower-to-ir.cpp
@@ -535,6 +535,8 @@ struct SharedIRGenContext
     //   in the source code.
     //
     List<IRInst*> m_stringLiterals;
+
+    DebugValueStoreContext debugValueContext;
 };
 
 struct IRGenContext;
@@ -9155,6 +9157,45 @@ struct DeclLoweringVisitor : DeclVisitor<DeclLoweringVisitor, LoweredValInfo>
             {
                 auto initVal = lowerRValueExpr(context, initExpr);
                 initVal = LoweredValInfo::simple(getSimpleVal(context, initVal));
+
+                // For debug builds, still create debug information for let variables
+                // even though we're not creating an actual variable
+                if (context->includeDebugInfo && decl->loc.isValid() &&
+                    context->shared->debugValueContext.isDebuggableType(initVal.val->getDataType()))
+                {
+                    // Create a debug variable for this let declaration
+                    auto builder = context->irBuilder;
+                    auto humaneLoc = context->getLinkage()->getSourceManager()->getHumaneLoc(
+                        decl->loc,
+                        SourceLocType::Emit);
+
+                    // Find the debug source for this file
+                    auto sourceView =
+                        context->getLinkage()->getSourceManager()->findSourceView(decl->loc);
+                    if (sourceView)
+                    {
+                        auto source = sourceView->getSourceFile();
+                        IRInst* debugSourceInst = nullptr;
+                        if (context->shared->mapSourceFileToDebugSourceInst.tryGetValue(
+                                source,
+                                debugSourceInst))
+                        {
+                            auto debugVar = builder->emitDebugVar(
+                                varType,
+                                debugSourceInst,
+                                builder->getIntValue(builder->getUIntType(), humaneLoc.line),
+                                builder->getIntValue(builder->getUIntType(), humaneLoc.column),
+                                nullptr);
+
+                            // Copy name hint from the declaration
+                            addNameHint(context, debugVar, decl);
+
+                            // Emit debug value to associate the constant with the debug variable
+                            builder->emitDebugValue(debugVar, initVal.val);
+                        }
+                    }
+                }
+
                 context->setGlobalValue(decl, initVal);
                 return initVal;
             }
@@ -12152,7 +12193,7 @@ RefPtr<IRModule> generateIRForTranslationUnit(
     // if debug symbols are enabled.
     if (context->includeDebugInfo)
     {
-        insertDebugValueStore(module);
+        insertDebugValueStore(context->shared->debugValueContext, module);
     }