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arm: avoid use of GNU builtin function in s_arm_unwind_save_mixed

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Whilst reviewing Luis' proposed change to s_arm_unwind_save_mixed
yesterday I noticed that we were making use of __builting_clzl
directly within the main function, which is not guaranteed to be
portable.  Whilst studying the code further, I also realized that it
could be rewritten without using it and also reworked to remove a lot
of unnecessary iterations steps.  So this patch does that (and also
removes the source of the warning that Luis was trying to fix).
Finally, with the rewrite we can also simplify the caller of this
routine as the new version can handle all the cases directly.

	* config/tc-arm.c (s_arm_unwind_save_mixed): Rewrite without
	using __builtin_clzl.
	(s_arm_unwind_save): Simplify logic for simple/mixed register saves.
This commit is contained in:
Richard Earnshaw 2022-05-26 11:05:59 +01:00
parent 284b6bb5c6
commit 20d814202a
1 changed files with 17 additions and 40 deletions
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57
gas/config/tc-arm.c
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@ -4716,39 +4716,29 @@ s_arm_unwind_save_mmxwcg (void)
ignore_rest_of_line ();
}
/* Convert range and mask_range into a sequence of s_arm_unwind_core
and s_arm_unwind_pseudo operations. We assume that mask_range will
not have consecutive bits set, or that one operation per bit is
acceptable. */
static void
s_arm_unwind_save_mixed (long range, long mask_range)
{
const long roof = ((sizeof (long) * CHAR_BIT) - 1)
- __builtin_clzl (mask_range);
long subrange = 0;
unsigned lim_lo = 0;
unsigned lim_hi = 0;
/* Iterate over pseudoregister to establish subrange bounds. */
for (; lim_hi <= roof; lim_hi++)
while (mask_range)
{
if (mask_range & (1 << lim_hi))
{
/* Once we know where to split our range, construct subrange. */
for (unsigned n = lim_lo; n < lim_hi; n++)
{
if (range & (1 << n))
subrange |= (1 << n);
}
long mask_bit = mask_range & -mask_range;
long subrange = range & (mask_bit - 1);
s_arm_unwind_save_core (subrange);
s_arm_unwind_save_pseudo (1 << lim_hi);
if (subrange)
s_arm_unwind_save_core (subrange);
subrange = 0;
lim_lo = lim_hi + 1;
}
s_arm_unwind_save_pseudo (mask_bit);
range &= ~subrange;
mask_range &= ~mask_bit;
}
lim_lo = 0xffff << roof;
subrange = range & lim_lo;
s_arm_unwind_save_core (subrange);
if (range)
s_arm_unwind_save_core (range);
}
/* Parse an unwind_save directive.
@ -4810,21 +4800,8 @@ s_arm_unwind_save (int arch_v6)
demand_empty_rest_of_line ();
if (!mask_range)
{
s_arm_unwind_save_core (range);
return;
}
else if (!range)
{
s_arm_unwind_save_pseudo (mask_range);
return;
}
else
{
s_arm_unwind_save_mixed (range, mask_range);
return;
}
s_arm_unwind_save_mixed (range, mask_range);
return;
case REG_TYPE_VFD:
if (arch_v6)