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Date:	Sun, 14 Jul 2013 19:30:00 +0000
From:	Tim Northover <>
To:	Linus Torvalds <>
Cc:	Ramkumar Ramachandra <>,
	Jeremy Fitzhardinge <>,
	Andi Kleen <>,
	LKML <>,
	LLVMdev <>,
	Thomas Gleixner <>,
	Ingo Molnar <>
Subject: Re: [LLVMdev] [PATCH] x86/asm: avoid mnemonics without type suffix

> And that is why I think you should just consider "bt $x,y" to be
> trivially the same thing and not at all ambiguous. Because there is
> ABSOLUTELY ZERO ambiguity when people write
>    bt $63, mem
> Zero. Nada. None. The semantics are *exactly* the same for btl and btq
> in this case, so why would you want the user to specify one or the
> other?

I don't think you've actually tested that, have you? (x86-64)

int main() {
  long val = 0xffffffff;
  char res;

  asm("btl $63, %1\n\tsetc %0" : "=r"(res) : "m"(val));
  printf("%d\n", res);

  asm("btq $63, %1\n\tsetc %0" : "=r"(res) : "m"(val));
  printf("%d\n", res);

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