[turbofan] Enforce that C calls do not use floating point params.

src/compiler/c-linkage.cc

Index: src/compiler/c-linkage.cc
diff --git a/src/compiler/c-linkage.cc b/src/compiler/c-linkage.cc
index cb47a7228d4e3ad5ba45fb9e5f94ad386a4b8b60..af9e0140b532975d1247da2f67be0648c2dac813 100644
--- a/src/compiler/c-linkage.cc
+++ b/src/compiler/c-linkage.cc
@@ -136,20 +136,19 @@ CallDescriptor* Linkage::GetSimplifiedCDescriptor(
     Zone* zone, const MachineSignature* msig, bool set_initialize_root_flag) {
   LocationSignature::Builder locations(zone, msig->return_count(),
                                        msig->parameter_count());
-#if 0  // TODO(titzer): instruction selector tests break here.
   // Check the types of the signature.
   // Currently no floating point parameters or returns are allowed because
   // on x87 and ia32, the FP top of stack is involved.
-
   for (size_t i = 0; i < msig->return_count(); i++) {
-    MachineType type = RepresentationOf(msig->GetReturn(i));
-    CHECK(type != kRepFloat32 && type != kRepFloat64);
+    MachineRepresentation rep = msig->GetReturn(i).representation();
+    CHECK(rep != MachineRepresentation::kFloat32 &&

[Benedikt Meurer, 2016/02/15 12:45:32]

Nit: two separate CHECKs instead of combining with &&

+          rep != MachineRepresentation::kFloat64);
   }
   for (size_t i = 0; i < msig->parameter_count(); i++) {
-    MachineType type = RepresentationOf(msig->GetParam(i));
-    CHECK(type != kRepFloat32 && type != kRepFloat64);
+    MachineRepresentation rep = msig->GetParam(i).representation();
+    CHECK(rep != MachineRepresentation::kFloat32 &&

[Benedikt Meurer, 2016/02/15 12:45:32]

Nit: two separate CHECKs instead of combining with &&

+          rep != MachineRepresentation::kFloat64);
   }
-#endif
 
 #ifdef UNSUPPORTED_C_LINKAGE
   // This method should not be called on unknown architectures.