Subzero: Always be sure x87 FP stack is emptied after a call.

src/IceTargetLoweringX8632.cpp

 //===- subzero/src/IceTargetLoweringX8632.cpp - x86-32 lowering -----------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the TargetLoweringX8632 class, which
@@ skipping 1882 matching lines @@
       Dest->setPreferredRegister(ReturnReg, false);
       if (isVectorType(Dest->getType())) {
         _movp(Dest, ReturnReg);
       } else {
         _mov(Dest, ReturnReg);
       }
     }
   } else if (Dest->getType() == IceType_f32 || Dest->getType() == IceType_f64) {
     // Special treatment for an FP function which returns its result in
     // st(0).
-    _fstp(Dest);
     // If Dest ends up being a physical xmm register, the fstp emit code
     // will route st(0) through a temporary stack slot.
+    _fstp(Dest);
+    // Create a fake use of Dest in case it actually isn't used,
+    // because st(0) still needs to be popped.
+    Context.insert(InstFakeUse::create(Func, Dest));
   }
 }
 
 void TargetX8632::lowerCast(const InstCast *Inst) {
   // a = cast(b) ==> t=cast(b); a=t; (link t->b, link a->t, no overlap)
   InstCast::OpKind CastKind = Inst->getCastKind();
   Variable *Dest = Inst->getDest();
   switch (CastKind) {
   default:
     Func->setError("Cast type not supported");
@@ skipping 2544 matching lines @@
     Str << "\t.align\t" << Align << "\n";
     Str << MangledName << ":\n";
     for (SizeT i = 0; i < Size; ++i) {
       Str << "\t.byte\t" << (((unsigned)Data[i]) & 0xff) << "\n";
     }
     Str << "\t.size\t" << MangledName << ", " << Size << "\n";
   }
 }
 
 } // end of namespace Ice