private int GetCallArgsRegionSize(AllocationResult allocResult, int maxCallArgs, out int xmmSaveRegionSize)
{
// We need to add 8 bytes to the total size, as the call to this
// function already pushed 8 bytes (the return address).
int intMask = CallingConvention.GetIntCalleeSavedRegisters() & allocResult.IntUsedRegisters;
int vecMask = CallingConvention.GetVecCalleeSavedRegisters() & allocResult.VecUsedRegisters;
xmmSaveRegionSize = BitUtils.CountBits(vecMask) * 16;
int calleeSaveRegionSize = BitUtils.CountBits(intMask) * 8 + xmmSaveRegionSize + 8;
int argsCount = maxCallArgs;
if (argsCount < 0)
{
// When the function has no calls, argsCount is -1.
// In this case, we don't need to allocate the shadow space.
argsCount = 0;
}
else if (argsCount < 4)
{
// The ABI mandates that the space for at least 4 arguments
// is reserved on the stack (this is called shadow space).
argsCount = 4;
}
int frameSize = calleeSaveRegionSize + allocResult.SpillRegionSize;
// TODO: Instead of always multiplying by 16 (the largest possible size of a variable,
// since a V128 has 16 bytes), we should calculate the exact size consumed by the
// arguments passed to the called functions on the stack.
int callArgsAndFrameSize = frameSize + argsCount * 16;
// Ensure that the Stack Pointer will be aligned to 16 bytes.
callArgsAndFrameSize = (callArgsAndFrameSize + 0xf) & ~0xf;
return(callArgsAndFrameSize - frameSize);
}
