s390x: [baseline] implement Switch

Change-Id: I9a4ba92f9da9cc964056d5c563b0534d9d172fcb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3412809Reviewed-by: Milad Farazmand <mfarazma@redhat.com>
Commit-Queue: Junliang Yan <junyan@redhat.com>
Cr-Commit-Position: refs/heads/main@{#78749}

src/baseline/s390/baseline-assembler-s390-inl.h

@@ -475,7 +475,29 @@ void BaselineAssembler::AddSmi(Register lhs, Smi rhs) { UNIMPLEMENTED(); }
 
 void BaselineAssembler::Switch(Register reg, int case_value_base,
                                Label** labels, int num_labels) {
-  UNIMPLEMENTED();
+  ASM_CODE_COMMENT(masm_);
+  Label fallthrough, jump_table;
+  if (case_value_base != 0) {
+    __ AddS64(reg, Operand(-case_value_base));
+  }
+
+  // Mostly copied from code-generator-arm.cc
+  ScratchRegisterScope scope(this);
+  JumpIf(Condition::kUnsignedGreaterThanEqual, reg, Operand(num_labels),
+         &fallthrough);
+  // Ensure to emit the constant pool first if necessary.
+  int entry_size_log2 = 3;
+  __ ShiftLeftU32(reg, reg, Operand(entry_size_log2));
+  __ larl(r1, &jump_table);
+  __ lay(reg, MemOperand(reg, r1));
+  __ b(reg);
+  __ b(&fallthrough);
+  __ bind(&jump_table);
+  for (int i = 0; i < num_labels; ++i) {
+    __ b(labels[i], Label::kFar);
+    __ nop();
+  }
+  __ bind(&fallthrough);
 }
 
 #undef __