Subzero: Fix a lowering bug involving xchg and xadd instructions.

src/IceTargetLoweringX8632.h

 //===- subzero/src/IceTargetLoweringX8632.h - x86-32 lowering ---*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file declares the TargetLoweringX8632 class, which
@@ skipping 242 matching lines @@
     Context.insert(InstX8632Cmpps::create(Func, Dest, Src0, Condition));
   }
   void _cmpxchg(Operand *DestOrAddr, Variable *Eax, Variable *Desired,
                 bool Locked) {
     Context.insert(
         InstX8632Cmpxchg::create(Func, DestOrAddr, Eax, Desired, Locked));
     // Mark eax as possibly modified by cmpxchg.
     Context.insert(
         InstFakeDef::create(Func, Eax, llvm::dyn_cast<Variable>(DestOrAddr)));
     _set_dest_nonkillable();
+    Context.insert(InstFakeUse::create(Func, Eax));
   }
   void _cmpxchg8b(OperandX8632Mem *Addr, Variable *Edx, Variable *Eax,
                   Variable *Ecx, Variable *Ebx, bool Locked) {
     Context.insert(
         InstX8632Cmpxchg8b::create(Func, Addr, Edx, Eax, Ecx, Ebx, Locked));
     // Mark edx, and eax as possibly modified by cmpxchg8b.
     Context.insert(InstFakeDef::create(Func, Edx));
     _set_dest_nonkillable();
+    Context.insert(InstFakeUse::create(Func, Edx));
     Context.insert(InstFakeDef::create(Func, Eax));
     _set_dest_nonkillable();
+    Context.insert(InstFakeUse::create(Func, Eax));
   }
   void _cvt(Variable *Dest, Operand *Src0, InstX8632Cvt::CvtVariant Variant) {
     Context.insert(InstX8632Cvt::create(Func, Dest, Src0, Variant));
   }
   void _div(Variable *Dest, Operand *Src0, Operand *Src1) {
     Context.insert(InstX8632Div::create(Func, Dest, Src0, Src1));
   }
   void _divps(Variable *Dest, Operand *Src0) {
     Context.insert(InstX8632Divps::create(Func, Dest, Src0));
   }
@@ skipping 178 matching lines @@
   void _test(Operand *Src0, Operand *Src1) {
     Context.insert(InstX8632Test::create(Func, Src0, Src1));
   }
   void _ucomiss(Operand *Src0, Operand *Src1) {
     Context.insert(InstX8632Ucomiss::create(Func, Src0, Src1));
   }
   void _ud2() { Context.insert(InstX8632UD2::create(Func)); }
   void _xadd(Operand *Dest, Variable *Src, bool Locked) {
     Context.insert(InstX8632Xadd::create(Func, Dest, Src, Locked));
     // The xadd exchanges Dest and Src (modifying Src).
-    // Model that update with a FakeDef.
+    // Model that update with a FakeDef followed by a FakeUse.
     Context.insert(
         InstFakeDef::create(Func, Src, llvm::dyn_cast<Variable>(Dest)));
     _set_dest_nonkillable();
+    Context.insert(InstFakeUse::create(Func, Src));
   }
   void _xchg(Operand *Dest, Variable *Src) {
     Context.insert(InstX8632Xchg::create(Func, Dest, Src));
-    // The xchg modifies Dest and Src -- model that update with a FakeDef.
+    // The xchg modifies Dest and Src -- model that update with a
+    // FakeDef/FakeUse.
     Context.insert(
         InstFakeDef::create(Func, Src, llvm::dyn_cast<Variable>(Dest)));
     _set_dest_nonkillable();
+    Context.insert(InstFakeUse::create(Func, Src));
   }
   void _xor(Variable *Dest, Operand *Src0) {
     Context.insert(InstX8632Xor::create(Func, Dest, Src0));
   }
   void _set_dest_nonkillable() {
     Context.getLastInserted()->setDestNonKillable();
   }
 
   const X86InstructionSet InstructionSet;
   bool IsEbpBasedFrame;
@@ skipping 34 matching lines @@
 };
 
 template <> void ConstantInteger32::emit(GlobalContext *Ctx) const;
 template <> void ConstantInteger64::emit(GlobalContext *Ctx) const;
 template <> void ConstantFloat::emit(GlobalContext *Ctx) const;
 template <> void ConstantDouble::emit(GlobalContext *Ctx) const;
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICETARGETLOWERINGX8632_H