Subzero: Use a setcc sequence for better icmp lowering.

src/IceInstX8632.h

Index: src/IceInstX8632.h
diff --git a/src/IceInstX8632.h b/src/IceInstX8632.h
index fca32c6ac49da9f172440843a8af72a58d4b0895..4ea2b36877311091afee77b51210e614eb0bdd01 100644
--- a/src/IceInstX8632.h
+++ b/src/IceInstX8632.h
@@ -242,6 +242,7 @@ public:
     Rol,
     Sar,
     Sbb,
+    Setcc,
     Shl,
     Shld,
     Shr,
@@ -1585,6 +1586,30 @@ private:
   ~InstX8632Ret() override {}
 };
 
+// Conditional set-byte instruction.
+class InstX8632Setcc : public InstX8632 {
+  InstX8632Setcc() = delete;
+  InstX8632Setcc(const InstX8632Cmov &) = delete;
+  InstX8632Setcc &operator=(const InstX8632Setcc &) = delete;
+
+public:
+  static InstX8632Setcc *create(Cfg *Func, Variable *Dest,
+                                CondX86::BrCond Cond) {
+    return new (Func->allocate<InstX8632Setcc>())
+        InstX8632Setcc(Func, Dest, Cond);
+  }
+  void emit(const Cfg *Func) const override;
+  void emitIAS(const Cfg *Func) const override;
+  void dump(const Cfg *Func) const override;
+  static bool classof(const Inst *Inst) { return isClassof(Inst, Setcc); }
+
+private:
+  InstX8632Setcc(Cfg *Func, Variable *Dest, CondX86::BrCond Cond);
+  ~InstX8632Setcc() override {}
+
+  const CondX86::BrCond Condition;
+};
+
 // Exchanging Add instruction.  Exchanges the first operand (destination
 // operand) with the second operand (source operand), then loads the sum
 // of the two values into the destination operand. The destination may be