[turbofan] Add basic support for calling to (a subset of) C functions.

src/compiler/linkage-impl.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_COMPILER_LINKAGE_IMPL_H_
 #define V8_COMPILER_LINKAGE_IMPL_H_
 
 #include "src/code-stubs.h"
 #include "src/compiler/osr.h"
 
@@ skipping 186 matching lines @@
 
   static CallDescriptor* GetSimplifiedCDescriptor(
       Zone* zone, const MachineSignature* msig) {
     LocationSignature::Builder locations(zone, msig->return_count(),
                                          msig->parameter_count());
     // Add return location(s).
     AddReturnLocations(&locations);
 
     // Add register and/or stack parameter(s).
     const int parameter_count = static_cast<int>(msig->parameter_count());
+    int stack_offset = LinkageTraits::CStackBackingStoreLength();
     for (int i = 0; i < parameter_count; i++) {
       if (i < LinkageTraits::CRegisterParametersLength()) {
         locations.AddParam(regloc(LinkageTraits::CRegisterParameter(i)));
       } else {
-        locations.AddParam(stackloc(-1 - i));
+        locations.AddParam(stackloc(-1 - stack_offset));
+        stack_offset++;
       }
     }
 
     // The target for C calls is always an address (i.e. machine pointer).
     MachineType target_type = kMachPtr;
     LinkageLocation target_loc = LinkageLocation::AnyRegister();
     return new (zone) CallDescriptor(           // --
         CallDescriptor::kCallAddress,           // kind
         target_type,                            // target MachineType
         target_loc,                             // target location
@@ skipping 62 matching lines @@
     int parameter_index = 1 + index;  // skip index 0, which is the target.
     return incoming_->GetInputLocation(parameter_index);
   }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_LINKAGE_IMPL_H_