Delete unused PoisonChecking utility pass

This was introduced ~5yrs ago (by me), and has never really gotten
any adoption.  By now, it's significantly out of sync with new/changed
poison propoagation rules.  The idea is still reasonable, but the
imagined use case is largely covered by alive2 these days anyways.

Author: preames

llvm/include/llvm/Transforms/Instrumentation/PoisonChecking.h

@@ -220,7 +220,6 @@
 #include "llvm/Transforms/Instrumentation/PGOCtxProfLowering.h"
 #include "llvm/Transforms/Instrumentation/PGOForceFunctionAttrs.h"
 #include "llvm/Transforms/Instrumentation/PGOInstrumentation.h"
-#include "llvm/Transforms/Instrumentation/PoisonChecking.h"
 #include "llvm/Transforms/Instrumentation/RealtimeSanitizer.h"
 #include "llvm/Transforms/Instrumentation/SanitizerBinaryMetadata.h"
 #include "llvm/Transforms/Instrumentation/SanitizerCoverage.h"

llvm/lib/Passes/PassBuilder.cpp

@@ -115,7 +115,6 @@ MODULE_PASS("partial-inliner", PartialInlinerPass())
 MODULE_PASS("pgo-icall-prom", PGOIndirectCallPromotion())
 MODULE_PASS("pgo-instr-gen", PGOInstrumentationGen())
 MODULE_PASS("pgo-instr-use", PGOInstrumentationUse())
-MODULE_PASS("poison-checking", PoisonCheckingPass())
 MODULE_PASS("pre-isel-intrinsic-lowering", PreISelIntrinsicLoweringPass(TM))
 MODULE_PASS("print", PrintModulePass(errs()))
 MODULE_PASS("print-callgraph", CallGraphPrinterPass(errs()))

llvm/lib/Passes/PassRegistry.def

@@ -19,7 +19,6 @@ add_llvm_component_library(LLVMInstrumentation
   PGOForceFunctionAttrs.cpp
   PGOInstrumentation.cpp
   PGOMemOPSizeOpt.cpp
-  PoisonChecking.cpp
   SanitizerCoverage.cpp
   SanitizerBinaryMetadata.cpp
   ValueProfileCollector.cpp