Extended Description

This code:

int value(uint64 b1, uint64 b2)
{
int i, j, k;
int value = 0;

for (k = 0; k < 2; k++)
for (i = 0; i < 6; i++)
for (j = 0; j < 2; j++)
if ((b2 & 0xf << (j + i * 6)) == 0xf << (j + i * 6))
value += 1000;

return value;
}

generates too many unnecessary spills/reloads when rerun through the optimizer (at -O2). See "***"
below:

LBB1_1: #bb17.preheader
movl $15, %eax
*** movb 39(%esp), %cl
movl %eax, %edx
shll %cl, %edx
*** movb 39(%esp), %cl
incb %cl
shll %cl, %eax
movl %edx, %ecx

The result is that the loop will run slower than if optimizations were turned on only once.