X64: Fix issue 678. Bug in some Win64 C calls from generated code.

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index b851fec68429b7cf63c50f12a2f794ba42769bc0..d82b8ecf381f9f52fe0941467a036b64c2d20013 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -2641,20 +2641,27 @@ void MacroAssembler::LoadContext(Register dst, int context_chain_length) {
   }
 }
 
+
 int MacroAssembler::ArgumentStackSlotsForCFunctionCall(int num_arguments) {
   // On Windows stack slots are reserved by the caller for all arguments
-  // including the ones passed in registers. On Linux 6 arguments are passed in
-  // registers and the caller does not reserve stack slots for them.
+  // including the ones passed in registers, and space is alwaysallocated for

[Rico, 2010/05/28 08:20:02]

always->allocated -> always allocated

+  // the four register arguments even if the function takes fewer than four
+  // arguments.
+  // On Linux the first six arguments are passed in registers and the caller
+  // does not reserve stack slots for them.
   ASSERT(num_arguments >= 0);
 #ifdef _WIN64
-  static const int kArgumentsWithoutStackSlot = 0;
+  static const int kMinimumStackSlots = 4;
+  if (num_arguments < kMinimumStackSlots) return kMinimumStackSlots;
+  return num_arguments;
 #else
-  static const int kArgumentsWithoutStackSlot = 6;
+  static const int kRegisterPassedArguments = 6;
+  if (num_arguments < kRegisterPassedArguments) return 0;
+  return num_arguments - kRegisterPassedArguments;
 #endif
-  return num_arguments > kArgumentsWithoutStackSlot ?
-      num_arguments - kArgumentsWithoutStackSlot : 0;
 }
 
+
 void MacroAssembler::PrepareCallCFunction(int num_arguments) {
   int frame_alignment = OS::ActivationFrameAlignment();
   ASSERT(frame_alignment != 0);