Fix DebugCompilationUnit to reference main shader file instead of header files (#7957)

This PR implements the requested fix for issue #7923 where
DebugCompilationUnit incorrectly referenced header files instead of the
main shader file.

## Summary

- Modified IRDebugSource to include isIncludedFile flag as third operand
- Updated emitDebugSource function to accept and pass the included file
flag
- Updated call sites to use source->isIncludedFile() from SourceFile
class
- Modified SPIR-V emission to only create DebugCompilationUnit for
non-included files

## Test Results

The fix has been verified with the provided reproducer code. The SPIR-V
output now correctly shows DebugCompilationUnit referencing the main
shader file instead of header files.

Generated with [Claude Code](https://claude.ai/code)

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Lujin Wang <lujinwangnv@users.noreply.github.com>
Co-authored-by: Claude Code <claude@anthropic.com>
Co-authored-by: slangbot <ellieh+slangbot@nvidia.com>
Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

7 files changed, 76 insertions, 8 deletions

diff --git a/source/slang/slang-emit-spirv.cpp b/source/slang/slang-emit-spirv.cpp
index f82bf24c1..18c54587a 100644
--- a/source/slang/slang-emit-spirv.cpp
+++ b/source/slang/slang-emit-spirv.cpp
@@ -2297,7 +2297,9 @@ struct SPIRVEmitContext : public SourceEmitterBase, public SPIRVEmitSharedContex
                 auto moduleInst = inst->getModule()->getModuleInst();
                 if (!m_defaultDebugSource)
                     m_defaultDebugSource = debugSource;
-                if (!m_mapIRInstToSpvDebugInst.containsKey(moduleInst))
+                // Only create DebugCompilationUnit for non-included files
+                auto isIncludedFile = as<IRBoolLit>(debugSource->getIsIncludedFile())->getValue();
+                if (!m_mapIRInstToSpvDebugInst.containsKey(moduleInst) && !isIncludedFile)
                 {
                     IRBuilder builder(inst);
                     builder.setInsertBefore(inst);
diff --git a/source/slang/slang-ir-insts.h b/source/slang/slang-ir-insts.h
index 9208e546c..e3014119c 100644
--- a/source/slang/slang-ir-insts.h
+++ b/source/slang/slang-ir-insts.h
@@ -3261,6 +3261,7 @@ struct IRDebugSource : IRInst
     FIDDLE(leafInst())
     IRInst* getFileName() { return getOperand(0); }
     IRInst* getSource() { return getOperand(1); }
+    IRInst* getIsIncludedFile() { return getOperand(2); }
 };
 
 FIDDLE()
@@ -3894,7 +3895,10 @@ public:
         return (IRMetalMeshType*)getType(kIROp_MetalMeshType, 5, ops);
     }
 
-    IRInst* emitDebugSource(UnownedStringSlice fileName, UnownedStringSlice source);
+    IRInst* emitDebugSource(
+        UnownedStringSlice fileName,
+        UnownedStringSlice source,
+        bool isIncludedFile);
     IRInst* emitDebugBuildIdentifier(UnownedStringSlice buildIdentifier, IRIntegerValue flags);
     IRInst* emitDebugBuildIdentifier(IRInst* debugBuildIdentifier);
     IRInst* emitDebugLine(
diff --git a/source/slang/slang-ir-insts.lua b/source/slang/slang-ir-insts.lua
index c1777c2cf..6487f36d0 100644
--- a/source/slang/slang-ir-insts.lua
+++ b/source/slang/slang-ir-insts.lua
@@ -2027,7 +2027,7 @@ local insts = {
 		EndFragmentShaderInterlock = { struct_name = "EndFragmentShaderInterlock" },
 	},
 	-- DebugInfo
-	{ DebugSource = { min_operands = 2, hoistable = true } },
+	{ DebugSource = { min_operands = 3, hoistable = true } },
 	{
 		DebugLine = {
 			min_operands = 5,
diff --git a/source/slang/slang-ir.cpp b/source/slang/slang-ir.cpp
index c63ca2bec..a61859a5e 100644
--- a/source/slang/slang-ir.cpp
+++ b/source/slang/slang-ir.cpp
@@ -3379,10 +3379,16 @@ IRInst* IRBuilder::emitOutImplicitCast(IRInst* type, IRInst* value)
 {
     return emitIntrinsicInst((IRType*)type, kIROp_OutImplicitCast, 1, &value);
 }
-IRInst* IRBuilder::emitDebugSource(UnownedStringSlice fileName, UnownedStringSlice source)
+IRInst* IRBuilder::emitDebugSource(
+    UnownedStringSlice fileName,
+    UnownedStringSlice source,
+    bool isIncludedFile)
 {
-    IRInst* args[] = {getStringValue(fileName), getStringValue(source)};
-    return emitIntrinsicInst(getVoidType(), kIROp_DebugSource, 2, args);
+    IRInst* args[] = {
+        getStringValue(fileName),
+        getStringValue(source),
+        getBoolValue(isIncludedFile)};
+    return emitIntrinsicInst(getVoidType(), kIROp_DebugSource, 3, args);
 }
 IRInst* IRBuilder::emitDebugBuildIdentifier(
     UnownedStringSlice buildIdentifier,
diff --git a/source/slang/slang-lower-to-ir.cpp b/source/slang/slang-lower-to-ir.cpp
index 3fbf0bda9..792848ce6 100644
--- a/source/slang/slang-lower-to-ir.cpp
+++ b/source/slang/slang-lower-to-ir.cpp
@@ -7486,7 +7486,7 @@ IRInst* getOrEmitDebugSource(IRGenContext* context, PathInfo path)
         content = UnownedStringSlice((char*)outBlob->getBufferPointer(), outBlob->getBufferSize());
     IRBuilder builder(*context->irBuilder);
     builder.setInsertInto(context->irBuilder->getModule());
-    auto debugSrcInst = builder.emitDebugSource(path.foundPath.getUnownedSlice(), content);
+    auto debugSrcInst = builder.emitDebugSource(path.foundPath.getUnownedSlice(), content, false);
     context->shared->mapSourcePathToDebugSourceInst[path.foundPath] = debugSrcInst;
     return debugSrcInst;
 }
@@ -12130,7 +12130,8 @@ RefPtr<IRModule> generateIRForTranslationUnit(
         {
             auto debugSource = builder->emitDebugSource(
                 source->getPathInfo().getMostUniqueIdentity().getUnownedSlice(),
-                source->getContent());
+                source->getContent(),
+                source->isIncludedFile());
             context->shared->mapSourceFileToDebugSourceInst.add(source, debugSource);
         }
     }
diff --git a/tests/spirv/debug-compilation-unit-main-file.slang b/tests/spirv/debug-compilation-unit-main-file.slang
new file mode 100644
index 000000000..c8e89ae93
--- /dev/null
+++ b/tests/spirv/debug-compilation-unit-main-file.slang
@@ -0,0 +1,37 @@
+//TEST:SIMPLE(filecheck=CHECK):-target spirv -entry main -stage fragment -g2 -emit-spirv-directly
+
+#include "shader-utils.slang"
+
+struct VertexOutput
+{
+    float4 position : SV_Position;
+    float2 texCoord : TEXCOORD0;
+}
+
+[shader("fragment")]
+float4 main(VertexOutput input) : SV_Target
+{
+    // Create a simple gradient pattern based on texture coordinates
+    float2 uv = input.texCoord;
+
+    // Call function from the included header file
+    float distanceFromCenter = calculateDistanceFromCenter(uv);
+
+    // Use another function from the header for a radial fade effect
+    float radialFade = createRadialFade(uv, 0.7);
+
+    // Create color pattern with both distance effects
+    float4 color = float4(
+        uv.x * (1.0 - distanceFromCenter * 0.5),  // Red with subtle distance fade
+        uv.y * radialFade,                        // Green with smooth radial fade
+        uv.x * uv.y,                              // Blue as product of coordinates
+        1.0                                       // Full opacity
+    );
+
+    return color;
+}
+
+// Verify that DebugCompilationUnit references this main shader file
+// CHECK: [[MAIN_FILE:%[0-9]+]] = OpString "{{.*}}debug-compilation-unit-main-file.slang"
+// CHECK: [[SOURCE_ID:%[0-9]+]] = OpExtInst %void %{{[0-9]+}} DebugSource [[MAIN_FILE]] %{{[0-9]+}}
+// CHECK: OpExtInst %void %{{[0-9]+}} DebugCompilationUnit %uint_{{[0-9]+}} %uint_{{[0-9]+}} [[SOURCE_ID]] %uint_{{[0-9]+}}
diff --git a/tests/spirv/shader-utils.slang b/tests/spirv/shader-utils.slang
new file mode 100644
index 000000000..967991ad3
--- /dev/null
+++ b/tests/spirv/shader-utils.slang
@@ -0,0 +1,18 @@
+#ifndef SHADER_UTILS_SLANG
+#define SHADER_UTILS_SLANG
+
+// Helper function to calculate distance from center
+float calculateDistanceFromCenter(float2 uv)
+{
+    float2 center = float2(0.5, 0.5);
+    return length(uv - center);
+}
+
+// Additional utility function - simple smoothstep fade
+float createRadialFade(float2 uv, float radius)
+{
+    float dist = calculateDistanceFromCenter(uv);
+    return smoothstep(radius, 0.0, dist);
+}
+
+#endif // SHADER_UTILS_SLANG
\ No newline at end of file