s390x: [liftoff][arm] Make context register allocatable

Port 4b3371c6

Original Message:
  This will make it easier to generate builtin calls that require the
  context to be passed in that register, because this can be represented
  as a {LiftoffRegister} then.

Change-Id: I35f14d9f5460706ef1d51f39a7eb3afdf0979f9d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2764682Reviewed-by: Milad Fa <mfarazma@redhat.com>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Junliang Yan <junyan@redhat.com>
Cr-Commit-Position: refs/heads/master@{#73543}

src/execution/s390/frame-constants-s390.h

@@ -47,7 +47,7 @@ class WasmCompileLazyFrameConstants : public TypedFrameConstants {
 class WasmDebugBreakFrameConstants : public TypedFrameConstants {
  public:
   static constexpr RegList kPushedGpRegs =
-      Register::ListOf(r2, r3, r4, r5, r6, r7, r8);
+      Register::ListOf(r2, r3, r4, r5, r6, r7, r8, cp);
 
   static constexpr RegList kPushedFpRegs = DoubleRegister::ListOf(
       d0, d1, d2, d3, d4, d5, d6, d7, d8, d9, d10, d11, d12);

src/wasm/baseline/liftoff-assembler-defs.h

@@ -72,7 +72,7 @@ constexpr RegList kLiftoffAssemblerFpCacheRegs = CPURegister::ListOf(
 #elif V8_TARGET_ARCH_S390X
 
 constexpr RegList kLiftoffAssemblerGpCacheRegs =
-    Register::ListOf(r2, r3, r4, r5, r6, r7, r8);
+    Register::ListOf(r2, r3, r4, r5, r6, r7, r8, cp);
 
 constexpr RegList kLiftoffAssemblerFpCacheRegs = DoubleRegister::ListOf(
     d0, d1, d2, d3, d4, d5, d6, d7, d8, d9, d10, d11, d12);