[x265] ASM crash in r6706

[Jason Garrett-Glaser]

> In this case, they pass a align stack to our code, but cglobal push 3
> registers, so broken stack align.

I don't understand what you mean.  x264asm knows what the stack
alignment is, so when it allocates scratch space, it references
aligned locations on the stack.  It doesn't matter how many registers
it pushes; if it pushes 12 bytes of registers, it references locations
that are 12 bytes off from where it would if there were no registers
pushed.

"esp" itself may not be aligned, but that's fine, because no data is
ever accessed directly from esp -- it's accessed from aligned
locations on the stack.  That's how stack alignment works. esp only
needs to be aligned if the function calls another function, but
x264asm is for leaf functions, so that doesn't apply.

Jason