PPC: [wasm] Int64Lowering of Int64Sub.

src/ppc/simulator-ppc.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stdarg.h>
 #include <stdlib.h>
 #include <cmath>
 
 #if V8_TARGET_ARCH_PPC
 
@@ skipping 2007 matching lines @@
       break;
     }
     case SUBFCX: {
       int rt = instr->RTValue();
       int ra = instr->RAValue();
       int rb = instr->RBValue();
       // int oe = instr->Bit(10);
       uintptr_t ra_val = get_register(ra);
       uintptr_t rb_val = get_register(rb);
       uintptr_t alu_out = ~ra_val + rb_val + 1;
+      // Set carry
+      if (ra_val <= rb_val) {
+        special_reg_xer_ = (special_reg_xer_ & ~0xF0000000) | 0x20000000;
+      } else {
+        special_reg_xer_ &= ~0xF0000000;
+      }
       set_register(rt, alu_out);
-      // If the sign of rb and alu_out don't match, carry = 0
-      if ((alu_out ^ rb_val) & 0x80000000) {
-        special_reg_xer_ &= ~0xF0000000;
-      } else {
-        special_reg_xer_ = (special_reg_xer_ & ~0xF0000000) | 0x20000000;
-      }
       if (instr->Bit(0)) {  // RC bit set
         SetCR0(alu_out);
       }
       // todo - handle OE bit
       break;
     }
+    case SUBFEX: {
+      int rt = instr->RTValue();
+      int ra = instr->RAValue();
+      int rb = instr->RBValue();
+      // int oe = instr->Bit(10);
+      uintptr_t ra_val = get_register(ra);
+      uintptr_t rb_val = get_register(rb);
+      uintptr_t alu_out = ~ra_val + rb_val;
+      if (special_reg_xer_ & 0x20000000) {
+        alu_out += 1;
+      }
+      set_register(rt, alu_out);
+      if (instr->Bit(0)) {  // RC bit set
+        SetCR0(static_cast<intptr_t>(alu_out));
+      }
+      // todo - handle OE bit
+      break;
+    }
     case ADDCX: {
       int rt = instr->RTValue();
       int ra = instr->RAValue();
       int rb = instr->RBValue();
       // int oe = instr->Bit(10);
       uintptr_t ra_val = get_register(ra);
       uintptr_t rb_val = get_register(rb);
       uintptr_t alu_out = ra_val + rb_val;
       // Set carry
       if (~ra_val < rb_val) {
@@ skipping 2060 matching lines @@
   uintptr_t* stack_slot = reinterpret_cast<uintptr_t*>(current_sp);
   uintptr_t address = *stack_slot;
   set_register(sp, current_sp + sizeof(uintptr_t));
   return address;
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // USE_SIMULATOR
 #endif  // V8_TARGET_ARCH_PPC