[mips][liftoff][mv] Remove multi-value overhead

Port 2332ebd8
https://crrev.com/c/2264099

Original Commit Message:

  - Add a separate function to load return slots, instead of encoding this
  in the offset,
  - Add fast path for single return.

Change-Id: I065c35b95dbc6546387ea54d298bb5765bc342cd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2269456Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Zhao Jiazhong <zhaojiazhong-hf@loongson.cn>
Cr-Commit-Position: refs/heads/master@{#68569}

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

@@ -46,9 +46,7 @@ constexpr int32_t kHighWordOffset = 4;
 // fp-4 holds the stack marker, fp-8 is the instance parameter.
 constexpr int kInstanceOffset = 8;
 
-inline MemOperand GetStackSlot(int offset) {
-  return MemOperand(offset > 0 ? fp : sp, -offset);
-}
+inline MemOperand GetStackSlot(int offset) { return MemOperand(fp, -offset); }
 
 inline MemOperand GetHalfStackSlot(int offset, RegPairHalf half) {
   int32_t half_offset =
@@ -600,6 +598,11 @@ void LiftoffAssembler::StoreCallerFrameSlot(LiftoffRegister src,
   liftoff::Store(this, fp, offset, src, type);
 }
 
+void LiftoffAssembler::LoadReturnStackSlot(LiftoffRegister dst, int offset,
+                                           ValueType type) {
+  liftoff::Load(this, dst, sp, offset, type);
+}
+
 void LiftoffAssembler::MoveStackValue(uint32_t dst_offset, uint32_t src_offset,
                                       ValueType type) {
   DCHECK_NE(dst_offset, src_offset);

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

@@ -42,9 +42,7 @@ namespace liftoff {
 // fp-8 holds the stack marker, fp-16 is the instance parameter.
 constexpr int kInstanceOffset = 16;
 
-inline MemOperand GetStackSlot(int offset) {
-  return MemOperand(offset > 0 ? fp : sp, -offset);
-}
+inline MemOperand GetStackSlot(int offset) { return MemOperand(fp, -offset); }
 
 inline MemOperand GetInstanceOperand() { return GetStackSlot(kInstanceOffset); }
 
@@ -529,6 +527,11 @@ void LiftoffAssembler::StoreCallerFrameSlot(LiftoffRegister src,
   liftoff::Store(this, fp, offset, src, type);
 }
 
+void LiftoffAssembler::LoadReturnStackSlot(LiftoffRegister dst, int offset,
+                                           ValueType type) {
+  liftoff::Load(this, dst, MemOperand(sp, offset), type);
+}
+
 void LiftoffAssembler::MoveStackValue(uint32_t dst_offset, uint32_t src_offset,
                                       ValueType type) {
   DCHECK_NE(dst_offset, src_offset);