Calling convention for ASM on Linux AMD64

[Sean O'Connor]

What calling convention is used for assembly language in Linux 
AMD64?
Normally the parameters go in fixed order into designated 
registers.

import std.stdio;
// Linux AMD64
float* test(float *x,ulong y){
	asm{
		naked;
		align 16;
		mov RAX,RDI;
		ret;
	}
}

void main(){
	float[] f=new float[16];
	writeln(&f[0]);
	float* a=test(&f[0],7);
	writeln(a);
}

If the ulong y parameter is removed from the function definition 
the pointer x goes into RDI as expected.  When y is added it all 
goes wrong. According to AMD64 the pointer should stay in RDI and 
the ulong go into RSI.