[mips] Support unaligned loading and storing kWord8 value

Change-Id: Ib5728e22815339096dec72cc3a6d8732da436062
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2437514Reviewed-by: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Zhao Jiazhong <zhaojiazhong-hf@loongson.cn>
Cr-Commit-Position: refs/heads/master@{#70211}

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

@@ -1388,9 +1388,9 @@ void InstructionSelector::VisitUnalignedLoad(Node* node) {
 
   ArchOpcode opcode = kArchNop;
   switch (load_rep.representation()) {
-    case MachineRepresentation::kBit:  // Fall through.
     case MachineRepresentation::kWord8:
-      UNREACHABLE();
+      opcode = load_rep.IsUnsigned() ? kMipsLbu : kMipsLb;
+      break;
     case MachineRepresentation::kWord16:
       opcode = load_rep.IsUnsigned() ? kMipsUlhu : kMipsUlh;
       break;
@@ -1409,6 +1409,7 @@ void InstructionSelector::VisitUnalignedLoad(Node* node) {
     case MachineRepresentation::kSimd128:
       opcode = kMipsMsaLd;
       break;
+    case MachineRepresentation::kBit:                // Fall through.
     case MachineRepresentation::kCompressedPointer:  // Fall through.
     case MachineRepresentation::kCompressed:         // Fall through.
     case MachineRepresentation::kWord64:             // Fall through.
@@ -1446,9 +1447,9 @@ void InstructionSelector::VisitUnalignedStore(Node* node) {
     case MachineRepresentation::kFloat64:
       opcode = kMipsUsdc1;
       break;
-    case MachineRepresentation::kBit:  // Fall through.
     case MachineRepresentation::kWord8:
-      UNREACHABLE();
+      opcode = kMipsSb;
+      break;
     case MachineRepresentation::kWord16:
       opcode = kMipsUsh;
       break;
@@ -1461,6 +1462,7 @@ void InstructionSelector::VisitUnalignedStore(Node* node) {
     case MachineRepresentation::kSimd128:
       opcode = kMipsMsaSt;
       break;
+    case MachineRepresentation::kBit:                // Fall through.
     case MachineRepresentation::kCompressedPointer:  // Fall through.
     case MachineRepresentation::kCompressed:         // Fall through.
     case MachineRepresentation::kWord64:             // Fall through.

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

@@ -1754,9 +1754,9 @@ void InstructionSelector::VisitUnalignedLoad(Node* node) {
     case MachineRepresentation::kFloat64:
       opcode = kMips64Uldc1;
       break;
-    case MachineRepresentation::kBit:  // Fall through.
     case MachineRepresentation::kWord8:
-      UNREACHABLE();
+      opcode = load_rep.IsUnsigned() ? kMips64Lbu : kMips64Lb;
+      break;
     case MachineRepresentation::kWord16:
       opcode = load_rep.IsUnsigned() ? kMips64Ulhu : kMips64Ulh;
       break;
@@ -1772,6 +1772,7 @@ void InstructionSelector::VisitUnalignedLoad(Node* node) {
     case MachineRepresentation::kSimd128:
       opcode = kMips64MsaLd;
       break;
+    case MachineRepresentation::kBit:                // Fall through.
     case MachineRepresentation::kCompressedPointer:  // Fall through.
     case MachineRepresentation::kCompressed:         // Fall through.
     case MachineRepresentation::kNone:
@@ -1806,9 +1807,9 @@ void InstructionSelector::VisitUnalignedStore(Node* node) {
     case MachineRepresentation::kFloat64:
       opcode = kMips64Usdc1;
       break;
-    case MachineRepresentation::kBit:  // Fall through.
     case MachineRepresentation::kWord8:
-      UNREACHABLE();
+      opcode = kMips64Sb;
+      break;
     case MachineRepresentation::kWord16:
       opcode = kMips64Ush;
       break;
@@ -1824,6 +1825,7 @@ void InstructionSelector::VisitUnalignedStore(Node* node) {
     case MachineRepresentation::kSimd128:
       opcode = kMips64MsaSt;
       break;
+    case MachineRepresentation::kBit:                // Fall through.
     case MachineRepresentation::kCompressedPointer:  // Fall through.
     case MachineRepresentation::kCompressed:         // Fall through.
     case MachineRepresentation::kNone: