[loong64][mips64] Cleanup some macros

Besides, fix a error in GetMemOp.

Port commit 247b33e9

Change-Id: I34cf0d22870f438fb6bfcd67ef50ec254fb92608
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3869758
Auto-Submit: Liu Yu <liuyu@loongson.cn>
Reviewed-by: Zhao Jiazhong <zhaojiazhong-hf@loongson.cn>
Commit-Queue: Zhao Jiazhong <zhaojiazhong-hf@loongson.cn>
Cr-Commit-Position: refs/heads/main@{#82928}

src/compiler/backend/mips64/instruction-selector-mips64.cc

@@ -3161,6 +3161,26 @@ SIMD_SHIFT_OP_LIST(SIMD_VISIT_SHIFT_OP)
 SIMD_BINOP_LIST(SIMD_VISIT_BINOP)
 #undef SIMD_VISIT_BINOP
 
+#define SIMD_RELAXED_OP_LIST(V)  \
+  V(F64x2RelaxedMin)             \
+  V(F64x2RelaxedMax)             \
+  V(F32x4RelaxedMin)             \
+  V(F32x4RelaxedMax)             \
+  V(I32x4RelaxedTruncF32x4S)     \
+  V(I32x4RelaxedTruncF32x4U)     \
+  V(I32x4RelaxedTruncF64x2SZero) \
+  V(I32x4RelaxedTruncF64x2UZero) \
+  V(I16x8RelaxedQ15MulRS)        \
+  V(I8x16RelaxedLaneSelect)      \
+  V(I16x8RelaxedLaneSelect)      \
+  V(I32x4RelaxedLaneSelect)      \
+  V(I64x2RelaxedLaneSelect)
+
+#define SIMD_VISIT_RELAXED_OP(Name) \
+  void InstructionSelector::Visit##Name(Node* node) { UNREACHABLE(); }
+SIMD_RELAXED_OP_LIST(SIMD_VISIT_RELAXED_OP)
+#undef SIMD_VISIT_SHIFT_OP
+
 void InstructionSelector::VisitS128Select(Node* node) {
   VisitRRRR(this, kMips64S128Select, node);
 }
@@ -3409,6 +3429,7 @@ InstructionSelector::AlignmentRequirements() {
 
 #undef SIMD_BINOP_LIST
 #undef SIMD_SHIFT_OP_LIST
+#undef SIMD_RELAXED_OP_LIST
 #undef SIMD_UNOP_LIST
 #undef SIMD_TYPE_LIST
 #undef TRACE_UNIMPL

src/wasm/baseline/mips64/liftoff-assembler-mips64.h

@@ -83,7 +83,7 @@ inline MemOperand GetMemOp(LiftoffAssembler* assm, Register addr,
                            bool i64_offset = false, unsigned shift_amount = 0) {
   if (offset != no_reg) {
     if (!i64_offset) {
-      assm->Dext(kScratchReg2, offset, 0, 32);
+      assm->Dext(kScratchReg, offset, 0, 32);
       offset = kScratchReg;
     }
     if (shift_amount != 0) {