PPC/s390: [wasm] Acquire the context for TrapIf from a wasm frame

Port 87d309da

Original Commit Message:

    This is the first step to reduce the size of the out-of-line code of
    TrapIf. Instead of passing the context to the runtime call as a
    parameter, we pass Smi::kZero to the runtime call and then get the
    actual context from the WasmFrame on the stack.

R=ahaas@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=v8:5908
LOG=N

Review-Url: https://codereview.chromium.org/2661363003
Cr-Commit-Position: refs/heads/master@{#42858}

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

@@ -2057,7 +2057,7 @@ void CodeGenerator::AssembleArchTrap(Instruction* instr,
             ExternalReference::wasm_call_trap_callback_for_testing(isolate()),
             0);
       } else {
-        __ Move(cp, isolate()->native_context());
+        __ Move(cp, Smi::kZero);
         gen_->AssembleSourcePosition(instr_);
         __ CallRuntime(trap_id);
       }

src/compiler/s390/code-generator-s390.cc

@@ -2300,7 +2300,7 @@ void CodeGenerator::AssembleArchTrap(Instruction* instr,
             ExternalReference::wasm_call_trap_callback_for_testing(isolate()),
             0);
       } else {
-        __ Move(cp, isolate()->native_context());
+        __ Move(cp, Smi::kZero);
         gen_->AssembleSourcePosition(instr_);
         __ CallRuntime(trap_id);
       }