http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60941
--- Comment #1 from Martin Husemann <martin at netbsd dot org> ---
Here is a small test program:
---8<---
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv)
{
unsigned long v[2], *p;
int a, b;
for (int i = 0; i < 2 && i < argc; i++) {
v[i] = atol(argv[i+1]) | 0xfff8800000000000;
printf("i = %d, got: %lx\n", i, v[i]);
}
p = &v[1];
a = *p-- & 0x0ffffffff;
b = *p & 0x0ffffffff;
printf("a = %08x b= %08x\n", a, b);
b = a << (b & 31);
*p = ((uint64_t)(uint32_t)b) | 0xfff8800000000000;
printf("res: %08lx\n", *p);
return 0;
}
--->8---
compile with c++ -Wall -O2 test.c and run as:
> ./a.out 26 1359893119
i = 0, got: fff880000000001a
i = 1, got: fff88000510e527f
a = 510e527f b= 0000001a
res: fffcb949fc000000
I would have expected res: 0xfff88000fc000000 (and on amd64 I get exactly that)
