gcc vs clang constant math compilation

clang -Os output

clang 3.4-1

0000000000000000 <hashit>:
   0:	b8 7e f5 35 6d       	mov    $0x6d35f57e,%eax
   5:	c3                   	retq   

gcc -Os output

gcc 4.8.2-14

0000000000000000 <hashit>:
   0:	8b 15 00 00 00 00    	mov    0x0(%rip),%edx        # 6 <hashit+0x6>
   6:	89 d0                	mov    %edx,%eax
   8:	c1 f8 10             	sar    $0x10,%eax
   b:	31 d0                	xor    %edx,%eax
   d:	69 d0 3b 9f 5d 04    	imul   $0x45d9f3b,%eax,%edx
  13:	89 d0                	mov    %edx,%eax
  15:	c1 f8 10             	sar    $0x10,%eax
  18:	31 d0                	xor    %edx,%eax
  1a:	69 d0 3b 9f 5d 04    	imul   $0x45d9f3b,%eax,%edx
  20:	89 d0                	mov    %edx,%eax
  22:	c1 f8 10             	sar    $0x10,%eax
  25:	31 d0                	xor    %edx,%eax
  27:	c3                   	retq   

source.c

int hashit (void) {
        const char *str = "abcd";
        int x = *(const int *)str;
        x = ((x >> 16) ^ x) * 0x45d9f3b;
        x = ((x >> 16) ^ x) * 0x45d9f3b;
        x = ((x >> 16) ^ x);
        return x;
}