ppc: Add STHBRX to assembler/disasm/simulator

Change-Id: Ie092921e4a9c1e4a0acee827f73570f3f9617712
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2971557Reviewed-by: Milad Fa <mfarazma@redhat.com>
Commit-Queue: Junliang Yan <junyan@redhat.com>
Cr-Commit-Position: refs/heads/master@{#75261}

src/codegen/ppc/constants-ppc.h

@@ -1244,6 +1244,8 @@ using Instr = uint32_t;
   V(stdbrx, STDBRX, 0x7C000528)                         \
   /* Store Word Byte-Reverse Indexed */                 \
   V(stwbrx, STWBRX, 0x7C00052C)                         \
+  /* Store Halfword Byte-Reverse Indexed */             \
+  V(sthbrx, STHBRX, 0x7C00072C)                         \
   /* Load Vector Indexed */                             \
   V(lvx, LVX, 0x7C0000CE)                               \
   /* Store Vector Indexed */                            \
@@ -1314,8 +1316,6 @@ using Instr = uint32_t;
   V(nand, NAND, 0x7C0003B8)                                                   \
   /* Parity Word */                                                           \
   V(prtyw, PRTYW, 0x7C000134)                                                 \
-  /* Store Halfword Byte-Reverse Indexed */                                   \
-  V(sthbrx, STHBRX, 0x7C00072C)                                               \
   /* Synchronize */                                                           \
   V(sync, SYNC, 0x7C0004AC)                                                   \
   /* Trap Word */                                                             \

src/diagnostics/ppc/disasm-ppc.cc

@@ -1117,6 +1117,10 @@ void Decoder::DecodeExt2(Instruction* instr) {
       Format(instr, "stwbrx  'rs, 'ra, 'rb");
       return;
     }
+    case STHBRX: {
+      Format(instr, "sthbrx  'rs, 'ra, 'rb");
+      return;
+    }
     case MTCRF: {
       Format(instr, "mtcrf   'FXM, 'rs");
       return;

src/execution/ppc/simulator-ppc.cc

@@ -2981,6 +2981,16 @@ void Simulator::ExecuteGeneric(Instruction* instr) {
       WriteW(ra_val + rb_val, __builtin_bswap32(rs_val));
       break;
     }
+    case STHBRX: {
+      int rs = instr->RSValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      intptr_t ra_val = ra == 0 ? 0 : get_register(ra);
+      intptr_t rs_val = get_register(rs);
+      intptr_t rb_val = get_register(rb);
+      WriteH(ra_val + rb_val, __builtin_bswap16(rs_val));
+      break;
+    }
     case STDX:
     case STDUX: {
       int rs = instr->RSValue();