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

src/compiler/ppc/code-generator-ppc.cc

Index: src/compiler/ppc/code-generator-ppc.cc
diff --git a/src/compiler/ppc/code-generator-ppc.cc b/src/compiler/ppc/code-generator-ppc.cc
index d7232bf3f9f558badc48aa6a98c047086b029091..9cc51466ae54837918164f33b70c43cf84fff924 100644
--- a/src/compiler/ppc/code-generator-ppc.cc
+++ b/src/compiler/ppc/code-generator-ppc.cc
@@ -34,6 +34,7 @@ class PPCOperandConverter final : public InstructionOperandConverter {
       case kFlags_branch:
       case kFlags_deoptimize:
       case kFlags_set:
+      case kFlags_trap:
         return SetRC;
       case kFlags_none:
         return LeaveRC;
@@ -2002,6 +2003,10 @@ void CodeGenerator::AssembleArchJump(RpoNumber target) {
   if (!IsNextInAssemblyOrder(target)) __ b(GetLabel(target));
 }
 
+void CodeGenerator::AssembleArchTrap(Instruction* instr,
+                                     FlagsCondition condition) {
+  UNREACHABLE();
+}
 
 // Assembles boolean materializations after an instruction.
 void CodeGenerator::AssembleArchBoolean(Instruction* instr,