Ignore unneeded kernel MD entries during partial recompilation

Whenever we enter a partial recompilation scenario, the successfully built
kernels are erased from the original SPV-friendly IR module. As it stands,
however, no metadata clean-up is performed for the unneeded kernels, and we
head straight into the unification phase with these dangling MD entries still
held by the original `!opencl.kernels` MD node. As it's turned out, the very
first occurence of such a dangling node can pollute the
`ModuleMetaData::FuncMD` map with a null key, which ends up breaking the
subsequent SPV-IR -> IGC metadata serialization routines.

This commit guards `ModuleMetaData::FuncMD` against dangling entries from the
initial compilation attempt: the LLVM function's validity is now checked
_before_ `operator[]` gets invoked on the map. This is more of an initial w/a -
instead, we should consider running a full cleanup within the compute interface
(or its retry manager utility), getting rid of obsolete metadata entries before
re-attempting the compilation.

Author: Artem Gindinson

IGC/AdaptorOCL/dllInterfaceCompute.cpp

@@ -1556,6 +1556,10 @@ bool TranslateBuildSPMD(
                         oclContext.m_retryManager.kernelSet.find(pFunc->getName().str()) == oclContext.m_retryManager.kernelSet.end())
                     {
                         pFunc->eraseFromParent();
+                        // TODO: Consider running a proper cleanup of
+                        // !opencl.kernels metadata entries here instead of
+                        // deferring 'null' entries to the "retried"
+                        // unification phase.
                     }
                 }
             }

IGC/Compiler/SPIRMetaDataTranslation.cpp

@@ -147,12 +147,15 @@ bool SPIRMetaDataTranslation::runOnModule(Module& M)
     {
         IGCMD::FunctionInfoMetaDataHandle fHandle = IGCMD::FunctionInfoMetaDataHandle(IGCMD::FunctionInfoMetaData::get());
         SPIRMD::KernelMetaDataHandle spirKernel = *ki;
+        // TODO: Null metadata entries are only expected in the event of a
+        // partial recompilation. Once the retry manager learns to clean
+        // up such metadata entries for unneeded kernels, we should simply
+        // assert on the function's validity instead.
+        if (spirKernel->getFunction() == nullptr)
+            continue;
         IGC::FunctionMetaData& funcMD = modMD->FuncMD[spirKernel->getFunction()];
         fHandle->setType(FunctionTypeMD::KernelFunction);
 
-        if(spirKernel->getFunction() == nullptr)
-            continue;
-
         // Handling Thread Group Size
         SPIRMD::WorkGroupDimensionsMetaDataHandle reqdWorkGroupSize = spirKernel->getRequiredWorkGroupSize();
         if (reqdWorkGroupSize->hasValue())

IGC/Compiler/tests/SPIRMetaDataTranslation/null-handling.ll

@@ -0,0 +1,53 @@
+;=========================== begin_copyright_notice ============================
+;
+; Copyright (C) 2023 Intel Corporation
+;
+; SPDX-License-Identifier: MIT
+;
+;============================ end_copyright_notice =============================
+;
+; RUN: igc_opt --serialize-igc-metadata -igc-spir-metadata-translation -S < %s | FileCheck %s
+; ------------------------------------------------
+; SPIRMetaDataTranslation
+; ------------------------------------------------
+
+; Check that during SPIRMetaData's propagation into IGCMetaData, 'null'
+; kernels are ignored by the translation/serialization routines.
+
+; TODO: Such null entries are typically encountered in partial recompilation
+; scenarios as leftovers from the initial compilation. Were the metadata
+; cleanup handled by retry manager routines, this test would no longer be
+; needed.
+
+declare spir_kernel void @test_spir(i64 addrspace(1)*)
+
+; CHECK: {!"FuncMDMap[0]", void (i64 addrspace(1)*)* @test_spir}
+; CHECK-NOT: {!"FuncMDMap[{{0-9}}]",
+
+!opencl.kernels = !{!0, !1, !12}
+!opencl.compiler.options = !{!19}
+
+; COM: The following kernel metadata sequence should be omitted by the pass
+!0 = distinct !{null, !13, !14, !15, !16, !17, !18}
+; COM: End null kernel sequence
+!1 = !{void (i64 addrspace(1)*)* @test_spir, !2, !3, !4, !5, !6, !7, !8, !9, !10, !11}
+!2 = !{!"kernel_arg_addr_space", i32 1}
+!3 = !{!"kernel_arg_access_qual", !"none"}
+!4 = !{!"kernel_arg_type", !"long*"}
+!5 = !{!"kernel_arg_type_qual", !"volatile"}
+!6 = !{!"kernel_arg_base_type", !"long*"}
+!7 = !{!"kernel_arg_name", !"dst"}
+!8 = !{!"reqd_work_group_size", i32 1, i32 1, i32 16}
+!9 = !{!"work_group_size_hint", i32 1, i32 1, i32 4}
+!10 = !{!"vec_type_hint", <4 x float> undef, i32 0}
+!11 = !{!"intel_reqd_sub_group_size", i32 16}
+; COM: The following kernel metadata sequence should be omitted by the pass
+!12 = distinct !{null, !13, !14, !15, !16, !17, !18}
+!13 = !{!"kernel_arg_addr_space", i32 0}
+!14 = !{!"kernel_arg_access_qual", !"none"}
+!15 = !{!"kernel_arg_type", !"void*"}
+!16 = !{!"kernel_arg_type_qual", !""}
+!17 = !{!"kernel_arg_base_type", !"void*"}
+!18 = !{!"kernel_arg_name", !"null_arg"}
+; COM: End null kernel sequence
+!19 = !{!"-cl-std=CL2.0", !"-cl-opt-disable", !"-g", !"-denorms-are-zero", !"-fp32-correctly-rounded-divide-sqrt", !"-mad-enable", !"-no-signed-zeros", !"-unsafe-math-optimizations", !"-finite-math-only", !"-fast-relaxed-math", !"-relaxed-builtins", !"-match-sincospi"}