Just for kicks, I compiled this code for ia64 and sparc64:
struct foo { int a; };
struct bar { int b; } __attribute__((packed));
int c(struct foo *x) { return x->a; }
int d(struct bar *x) { return x->b; }
The ia64 assembly for d() does not look pretty:
0000000000000000 <c>:
0: 0a 10 00 18 00 21 [MMI] mov r2=r12;;
6: 00 00 09 30 23 00 st8 [r2]=r32
c: 00 00 04 00 nop.i 0x0
10: 0b 70 00 04 18 10 [MMI] ld8 r14=[r2];;
16: e0 00 38 20 20 00 ld4 r14=[r14]
1c: 00 00 04 00 nop.i 0x0;;
20: 11 40 00 1c 00 21 [MIB] mov r8=r14
26: c0 00 08 00 42 80 mov r12=r2
2c: 08 00 84 00 br.ret.sptk.many b0;;
0000000000000030 <d>:
30: 0a 10 00 18 00 21 [MMI] mov r2=r12;;
36: 00 00 09 30 23 00 st8 [r2]=r32
3c: 00 00 04 00 nop.i 0x0
40: 0b 78 00 04 18 10 [MMI] ld8 r15=[r2];;
46: 00 01 3c 00 20 c0 ld1 r16=[r15]
4c: 11 78 00 84 adds r14=1,r15;;
50: 0b 70 00 1c 00 10 [MMI] ld1 r14=[r14];;
56: 00 00 00 02 00 c0 nop.m 0x0
5c: e1 b8 dd 53 shl r14=r14,8;;
60: 0d 80 40 1c 0e 20 [MFI] or r16=r16,r14
66: 00 00 00 02 00 c0 nop.f 0x0
6c: 21 78 00 84 adds r14=2,r15;;
70: 0b 70 00 1c 00 10 [MMI] ld1 r14=[r14];;
76: 00 00 00 02 00 c0 nop.m 0x0
7c: e1 78 bd 53 shl r14=r14,16;;
80: 0d 80 40 1c 0e 20 [MFI] or r16=r16,r14
86: 00 00 00 02 00 c0 nop.f 0x0
8c: 31 78 00 84 adds r14=3,r15;;
90: 0b 70 00 1c 00 10 [MMI] ld1 r14=[r14];;
96: 00 00 00 02 00 c0 nop.m 0x0
9c: e1 38 9d 53 shl r14=r14,24;;
a0: 0b 70 40 1c 0e 20 [MMI] or r14=r16,r14;;
a6: 00 00 00 02 00 c0 nop.m 0x0
ac: e1 f8 7c 53 shl r14=r14,32;;
b0: 02 00 00 00 01 00 [MII] nop.m 0x0
b6: e0 08 3a 3e 29 00 shr r14=r14,32;;
bc: 01 70 00 84 mov r8=r14
c0: 1d 60 00 04 00 21 [MFB] mov r12=r2
c6: 00 00 00 02 00 80 nop.f 0x0
cc: 08 00 84 00 br.ret.sptk.many b0;;
On sparc64, d() looks similarly terrible:
0000000000000000 <c>:
0: 9d e3 bf 40 save %sp, -192, %sp
4: f0 77 a8 7f stx %i0, [ %fp + 0x87f ]
8: c2 5f a8 7f ldx [ %fp + 0x87f ], %g1
c: c2 00 40 00 ld [ %g1 ], %g1
10: 83 38 60 00 sra %g1, 0, %g1
14: b0 10 00 01 mov %g1, %i0
18: 81 cf e0 08 rett %i7 + 8
1c: 01 00 00 00 nop
0000000000000020 <d>:
20: 9d e3 bf 40 save %sp, -192, %sp
24: f0 77 a8 7f stx %i0, [ %fp + 0x87f ]
28: c4 5f a8 7f ldx [ %fp + 0x87f ], %g2
2c: c2 08 80 00 ldub [ %g2 ], %g1
30: 82 08 60 ff and %g1, 0xff, %g1
34: 87 28 70 18 sllx %g1, 0x18, %g3
38: c2 08 a0 01 ldub [ %g2 + 1 ], %g1
3c: 82 08 60 ff and %g1, 0xff, %g1
40: 83 28 70 10 sllx %g1, 0x10, %g1
44: 86 10 40 03 or %g1, %g3, %g3
48: c2 08 a0 02 ldub [ %g2 + 2 ], %g1
4c: 82 08 60 ff and %g1, 0xff, %g1
50: 83 28 70 08 sllx %g1, 8, %g1
54: 86 10 40 03 or %g1, %g3, %g3
58: c2 08 a0 03 ldub [ %g2 + 3 ], %g1
5c: 82 08 60 ff and %g1, 0xff, %g1
60: 82 10 40 03 or %g1, %g3, %g1
64: 83 28 70 20 sllx %g1, 0x20, %g1
68: 83 38 70 20 srax %g1, 0x20, %g1
6c: 83 38 60 00 sra %g1, 0, %g1
70: b0 10 00 01 mov %g1, %i0
74: 81 cf e0 08 rett %i7 + 8
78: 01 00 00 00 nop
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