[WebAssembly] Represent trap instructions as poison (#134553)

The WebAssemblyLowerRefTypesIntPtrConv pass currently uses `undef` to
represent trap instructions. These can instead be represented by the
`poison` value.

Author: pedroclobo

llvm/lib/Target/WebAssembly/WebAssemblyLowerRefTypesIntPtrConv.cpp

@@ -68,8 +68,7 @@ bool WebAssemblyLowerRefTypesIntPtrConv::runOnFunction(Function &F) {
         !(ITP && WebAssembly::isWebAssemblyReferenceType(ITP->getDestTy())))
       continue;
 
-    UndefValue *U = UndefValue::get(I->getType());
-    I->replaceAllUsesWith(U);
+    I->replaceAllUsesWith(PoisonValue::get(I->getType()));
 
     Function *TrapIntrin =
         Intrinsic::getOrInsertDeclaration(F.getParent(), Intrinsic::debugtrap);