[wasm] Introduce the TrapIf and TrapUnless operators to generate trap code.

src/compiler/ppc/instruction-selector-ppc.cc

Index: src/compiler/ppc/instruction-selector-ppc.cc
diff --git a/src/compiler/ppc/instruction-selector-ppc.cc b/src/compiler/ppc/instruction-selector-ppc.cc
index bf50ea4e6ebd4727732a56a0513ca4ffac3c41e5..d09038ce7ebe2c34009ecf0e18fc578d08868e51 100644
--- a/src/compiler/ppc/instruction-selector-ppc.cc
+++ b/src/compiler/ppc/instruction-selector-ppc.cc
@@ -1787,6 +1787,10 @@ void InstructionSelector::VisitDeoptimizeUnless(Node* node) {
   VisitWord32CompareZero(this, node, node->InputAt(0), &cont);
 }
 
+void InstructionSelector::VisitTrapIf(Node* node) { UNREACHABLE(); }
+
+void InstructionSelector::VisitTrapUnless(Node* node) { UNREACHABLE(); }
+
 void InstructionSelector::VisitSwitch(Node* node, const SwitchInfo& sw) {
   PPCOperandGenerator g(this);
   InstructionOperand value_operand = g.UseRegister(node->InputAt(0));