Re: [PATCH] Fix ICE with x87 asm operands (PR inline-asm/68843)

[Uros Bizjak <ubizjak at gmail dot com>]

On Sun, May 22, 2016 at 9:00 AM, Bernd Edlinger
<bernd.edlinger@hotmail.de> wrote:
> Hi!
>
> as described in the PR there are several non-intuitive rules that
> one has to follow to avoid ICEs with x87 asm operands.
>
> This patch adds an explicit rule, that avoids ICE in the first test case and
> removes an unnecessary error message in the second test case.
>
>
> Boot-strapped and regression-tested on x86_64-pc-linux-gnu.
> OK for trunk?

This patch is actually dealing with two separate problems

This part:

@@ -607,7 +631,7 @@ check_asm_stack_operands (rtx_insn *insn)
      record any earlyclobber.  */

   for (i = n_outputs; i < n_outputs + n_inputs; i++)
-    if (op_alt[i].matches == -1)
+    if (op_alt[i].matches == -1 && STACK_REG_P (recog_data.operand[i]))
       {
  int j;

is OK, although, I'd written it as:


+    if (STACK_REG_P (recog_data.operand[i]) && op_alt[i].matches == -1)

with slightly simplified testcase:

--cut here--
int
__attribute__((noinline, noclone))
test (double y)
{
  int a, b;
  asm ("fistpl (%1)\n\t"
       "movl (%1), %0"
       : "=r" (a)
       : "r" (&b), "t" (y)
       : "st");
  return a;
}

int
main ()
{
  int t = -10;

  if (test (t) != t)
    __builtin_abort ();
  return 0;
}
--cut here--

BTW: It looks to me you also don't need all-memory clobber here.

This part is OK, with a testcase you provided it borders on obvious.
However, you will need rtl-optimization approval for the other
problem.

Uros.