[wasm] Int64Lowering of Int64Sub on ia32 and arm.

src/arm/simulator-arm.cc

Index: src/arm/simulator-arm.cc
diff --git a/src/arm/simulator-arm.cc b/src/arm/simulator-arm.cc
index 7687bbbe7c91f123db176c08f5a78f26df477142..490d9617ada877641eae503803ad5a8bc8d1d1a9 100644
--- a/src/arm/simulator-arm.cc
+++ b/src/arm/simulator-arm.cc
@@ -1333,11 +1333,12 @@ bool Simulator::CarryFrom(int32_t left, int32_t right, int32_t carry) {
 
 
 // Calculate C flag value for subtractions.
-bool Simulator::BorrowFrom(int32_t left, int32_t right) {
+bool Simulator::BorrowFrom(int32_t left, int32_t right, int32_t carry) {
   uint32_t uleft = static_cast<uint32_t>(left);
   uint32_t uright = static_cast<uint32_t>(right);
 
-  return (uright > uleft);
+  return (uright > uleft) ||
+         (carry && (((uright + 1) > uleft) || (uright > (uleft - 1))));
 }
 
 
@@ -2493,8 +2494,15 @@ void Simulator::DecodeType01(Instruction* instr) {
       }
 
       case SBC: {
-        Format(instr, "sbc'cond's 'rd, 'rn, 'shift_rm");
-        Format(instr, "sbc'cond's 'rd, 'rn, 'imm");
+        //        Format(instr, "sbc'cond's 'rd, 'rn, 'shift_rm");
+        //        Format(instr, "sbc'cond's 'rd, 'rn, 'imm");
+        alu_out = (rn_val - shifter_operand) - (GetCarry() ? 0 : 1);

[titzer, 2016/03/14 09:36:06]

Why is carry inverted here?

[ahaas, 2016/03/15 11:01:43]

Because the arm instruction manual says so.

+        set_register(rd, alu_out);
+        if (instr->HasS()) {
+          SetNZFlags(alu_out);
+          SetCFlag(!BorrowFrom(rn_val, shifter_operand, GetCarry()));
+          SetVFlag(OverflowFrom(alu_out, rn_val, shifter_operand, false));
+        }
         break;
       }