[SPIRV] Fix pcf with rich debug info enabled (microsoft#7663)

Compilation crashes when generating the patch constant function when
rich debug info is enabled. This PR corrects the issue, which was
reported in
microsoft#7311

Author: SteveUrquhart

tools/clang/lib/SPIRV/SpirvEmitter.cpp

@@ -1591,8 +1591,15 @@ void SpirvEmitter::doFunctionDecl(const FunctionDecl *decl) {
   if (spirvOptions.debugInfoRich) {
     if (srcDebugFunction) {
       spvContext.pushDebugLexicalScope(info, srcDebugFunction);
-    } else {
+    } else if (debugFunction) {
       spvContext.pushDebugLexicalScope(info, debugFunction);
+    } else {
+      // A function which is not called directly in HLSL, and therefore does not
+      // reside in the workQueue
+      if (decl->hasBody()) {
+        debugFunction = emitDebugFunction(decl, func, &info, funcName);
+        spvContext.pushDebugLexicalScope(info, debugFunction);
+      }
     }
   }
 

tools/clang/test/CodeGenSPIRV/shader.debug.pcf.hlsl

@@ -0,0 +1,35 @@
+// RUN: %dxc -T hs_6_0 -E HS -fspv-debug=vulkan-with-source -fcgl %s -spirv | FileCheck %s
+
+// CHECK:            [[set:%[0-9]+]] = OpExtInstImport "NonSemantic.Shader.DebugInfo.100"
+// CHECK: [[hsConstantName:%[0-9]+]] = OpString "hsConstant"
+// CHECK:    [[dbgFunction:%[0-9]+]] = OpExtInst %void [[set]] DebugFunction [[hsConstantName]]
+// CHECK:   [[lexicalBlock:%[0-9]+]] = OpExtInst %void [[set]] DebugLexicalBlock {{%[0-9]+}} %uint_23 %uint_1 [[dbgFunction]]
+// CHECK:                %hsConstant = OpFunction %HS_OUTPUT None {{%[0-9]+}}
+// CHECK:                {{%[0-9]+}} = OpExtInst %void [[set]] DebugFunctionDefinition [[dbgFunction]] %hsConstant
+// CHECK:                {{%[0-9]+}} = OpExtInst %void [[set]] DebugScope [[lexicalBlock]]
+
+struct HS_OUTPUT
+{
+	float edges[4] : SV_TessFactor;
+	float inside[2]: SV_InsideTessFactor;
+};
+
+struct VS_OUTPUT
+{
+    float4 pos	: POSITION;
+};
+
+HS_OUTPUT hsConstant( InputPatch<VS_OUTPUT, 4> ip, uint pid : SV_PrimitiveID )
+{	
+	return (HS_OUTPUT)0;
+}
+
+[domain("quad")]
+[partitioning("integer")]
+[outputcontrolpoints(4)]
+[outputtopology("triangle_cw")]
+[patchconstantfunc("hsConstant")]
+VS_OUTPUT HS( InputPatch<VS_OUTPUT, 4> ip, uint cpid : SV_OutputControlPointID)
+{
+	return (VS_OUTPUT)0;
+}