https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80808
--- Comment #2 from Jakub Jelinek ---
Smaller testcase that still works at -O1 and fails at -O2 (+ -march=armv7-a
-mfpu=vfpv3-d16 -mfloat-abi=hard in both cases):
static __attribute__ ((noinline, noclone)) unsigned
mpihelp_divrem (unsigned *qp, int qextra_limbs,
unsigned *np, int nsize,
unsigned *dp, int dsize)
{
unsigned most_significant_q_limb = 0;
switch (dsize)
{
case 0:
return 1 / dsize;
case 2:
{
int i;
unsigned n1, n0, n2, d1, d0;
np += nsize - 2;
d1 = dp[1];
d0 = dp[0];
n1 = np[1];
n0 = np[0];
if (n1 >= d1 && (n1 > d1 || n0 >= d0))
{
__asm__ ("subs %1, %4, %5\n" "sbc %0, %2, %3"
: "=r" (n1), "=" (n0)
: "r" (n1), "rI" (d1), "r" (n0), "rI" (d0));
most_significant_q_limb = 1;
}
for (i = qextra_limbs + nsize - 2 - 1; i >= 0; i--)
{
unsigned q;
unsigned r;
if (i >= qextra_limbs)
np--;
else
np[0] = 0;
if (n1 == d1)
{
q = ~(unsigned) 0;
r = n0 + d1;
if (r < d1)
{
__asm__ ("adds %1, %4, %5\n" "adc %0, %2, %3"
: "=r" (n1), "=" (n0)
: "%r" (r - d0), "rI" (0),
"%r" (np[0]), "rI" (d0));
qp[i] = q;
continue;
}
n1 = d0 - (d0 != 0 ? 1 : 0);
n0 = -d0;
}
else
{
do
{
unsigned __d1, __d0, __q1, __q0, __r1, __r0, __m;
__d1 = (d1 >> ((8 * (4)) / 2));
__d0 = (d1 & ((1U << ((8 * (4)) / 2)) - 1));
__r1 = (n1) % __d1;
__q1 = (n1) / __d1;
__m = (unsigned) __q1 *__d0;
__r1 = __r1 * (1U << ((8 * (4)) / 2))
| ((unsigned) (n0) >> ((8 * (4)) / 2));
if (__r1 < __m)
{
__q1--, __r1 += (d1);
if (__r1 >= (d1))
if (__r1 < __m)
__q1--, __r1 += (d1);
}
__r1 -= __m;
__r0 = __r1 % __d1;
__q0 = __r1 / __d1;
__m = (unsigned) __q0 *__d0;
__r0 = __r0 * (1U << ((8 * (4)) / 2))
| (n0 & (((unsigned) 1 << ((8 * (4)) / 2)) - 1));
if (__r0 < __m)
{
__q0--, __r0 += (d1);
if (__r0 >= (d1))
if (__r0 < __m)
__q0--, __r0 += (d1);
}
__r0 -= __m;
q = (unsigned) __q1 * (1U << ((8 * (4)) / 2)) | __q0;
r = __r0;
}
while (0);
__asm__ ("umull %r1, %r0, %r2, %r3"
: "=" (n1), "=r" (n0)
: "r" (d0), "r" (q):"r0", "r1");
}
n2 = np[0];
q_test:
if (n1 > r || (n1 == r && n0 > n2))
{
q--;
__asm__ ("subs %1, %4, %5\n" "sbc %0, %2, %3"
: "=r" (n1), "=" (n0)
: "r" (n1), "rI" (0), "r" (n0), "rI" (d0));
r += d1;
if (r >= d1)
goto q_test;
}
qp[i] = q;
__asm__ ("subs %1, %4, %5\n" "sbc %0, %2, %3"
: "=r" (n1), "=" (n0)
: "r" (r), "rI" (n1), "r" (n2), "rI" (n0));
}
np[1] = n1;
np[0] = n0;
}
break;
default:
__builtin_abort ();
}
return most_significant_q_limb;
}
int
main ()
{
unsigned qp[1];
unsigned np[3] = { 0xdaafeaa6, 0x0e77816a, 1 };
unsigned dp[2] = { 0x6816ec64, 0xb9d5666d };
volatile int l = 0;
unsigned ret = mpihelp_divrem (qp + l, 0 + l, np + l, 3 + l, dp + l, 2 + l);
if (ret != 0 || qp[0] != 1 || np[0] != 0x7298fe42 || np[1] != 0x54a21afd)
__builtin_abort ();
return 0;
}
