PPC: [wasm] Int64Lowering of Int64Sub.

src/ppc/simulator-ppc.cc

Index: src/ppc/simulator-ppc.cc
diff --git a/src/ppc/simulator-ppc.cc b/src/ppc/simulator-ppc.cc
index 817e75626282ce9595d4814086844264777c98b5..123ceb8838d574a5e0d43352920640e587af59b9 100644
--- a/src/ppc/simulator-ppc.cc
+++ b/src/ppc/simulator-ppc.cc
@@ -2025,19 +2025,37 @@ bool Simulator::ExecuteExt2_9bit_part1(Instruction* instr) {
       uintptr_t ra_val = get_register(ra);
       uintptr_t rb_val = get_register(rb);
       uintptr_t alu_out = ~ra_val + rb_val + 1;
-      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 {
+      // 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 (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();