Re: [PATCH 9/7] blktrace: simplify flags handling in __blk_add_trace

[David Woodhouse <dwmw2@infradead.org>]

On Sun, 2008-08-10 at 12:48 +0100, David Woodhouse wrote:
> On PPC64 this reduces the size of the code calculating these bits by
> about 60%. 

(gdb) disass make_what_old
Dump of assembler code for function make_what_old:
0x0000000000000000 <make_what_old+0>:	std     r30,-16(r1)
0x0000000000000004 <make_what_old+4>:	ld      r30,0(r2)
0x0000000000000008 <make_what_old+8>:	rlwinm  r9,r3,29,30,30
0x000000000000000c <make_what_old+12>:	rlwinm  r10,r3,1,29,29
0x0000000000000010 <make_what_old+16>:	extsw   r9,r9
0x0000000000000014 <make_what_old+20>:	rlwinm  r7,r3,0,29,29
0x0000000000000018 <make_what_old+24>:	ld      r8,-32768(r30)
0x000000000000001c <make_what_old+28>:	rldicr  r9,r9,2,61
0x0000000000000020 <make_what_old+32>:	rlwinm  r11,r3,30,28,28
0x0000000000000024 <make_what_old+36>:	ld      r30,-16(r1)
0x0000000000000028 <make_what_old+40>:	extsw   r10,r10
0x000000000000002c <make_what_old+44>:	rlwinm  r0,r3,30,27,27
0x0000000000000030 <make_what_old+48>:	rldicr  r10,r10,2,61
0x0000000000000034 <make_what_old+52>:	extsw   r11,r11
0x0000000000000038 <make_what_old+56>:	lwzx    r9,r8,r9
0x000000000000003c <make_what_old+60>:	lwzx    r3,r8,r7
0x0000000000000040 <make_what_old+64>:	extsw   r0,r0
0x0000000000000044 <make_what_old+68>:	rldicr  r11,r11,2,61
0x0000000000000048 <make_what_old+72>:	or      r3,r3,r9
0x000000000000004c <make_what_old+76>:	rldicr  r0,r0,2,61
0x0000000000000050 <make_what_old+80>:	lwzx    r9,r8,r10
0x0000000000000054 <make_what_old+84>:	or      r3,r3,r4
0x0000000000000058 <make_what_old+88>:	lwzx    r11,r8,r11
0x000000000000005c <make_what_old+92>:	or      r3,r3,r9
0x0000000000000060 <make_what_old+96>:	lwzx    r0,r8,r0
0x0000000000000064 <make_what_old+100>:	or      r3,r3,r11
0x0000000000000068 <make_what_old+104>:	or      r3,r3,r0
0x000000000000006c <make_what_old+108>:	clrldi  r3,r3,32
0x0000000000000070 <make_what_old+112>:	blr
End of assembler dump.
(gdb) disass make_what_new
Dump of assembler code for function make_what_new:
0x0000000000000074 <make_what_new+0>:	mr      r0,r3
0x0000000000000078 <make_what_new+4>:	rlwinm  r3,r3,16,13,13
0x000000000000007c <make_what_new+8>:	rlwinm  r9,r0,15,12,12
0x0000000000000080 <make_what_new+12>:	rlwinm  r11,r0,26,4,4
0x0000000000000084 <make_what_new+16>:	or      r3,r3,r9
0x0000000000000088 <make_what_new+20>:	rlwinm  r9,r0,23,3,3
0x000000000000008c <make_what_new+24>:	or      r3,r3,r4
0x0000000000000090 <make_what_new+28>:	rlwinm  r0,r0,23,2,2
0x0000000000000094 <make_what_new+32>:	or      r3,r3,r11
0x0000000000000098 <make_what_new+36>:	or      r3,r3,r9
0x000000000000009c <make_what_new+40>:	or      r3,r3,r0
0x00000000000000a0 <make_what_new+44>:	clrldi  r3,r3,32
0x00000000000000a4 <make_what_new+48>:	blr
End of assembler dump.

> On x86_64 it's less of a win -- only 40%.

(gdb) disass make_what_old
Dump of assembler code for function make_what_old:
0x0000000000000000 <make_what_old+0>:	mov    %edi,%edx
0x0000000000000002 <make_what_old+2>:	mov    %rdi,%rax
0x0000000000000005 <make_what_old+5>:	push   %rbp
0x0000000000000006 <make_what_old+6>:	and    $0x10,%edx
0x0000000000000009 <make_what_old+9>:	and    $0x4,%eax
0x000000000000000c <make_what_old+12>:	sar    $0x3,%edx
0x000000000000000f <make_what_old+15>:	mov    0x0(%rax),%eax
0x0000000000000015 <make_what_old+21>:	mov    %rsp,%rbp
0x0000000000000018 <make_what_old+24>:	movslq %edx,%rdx
0x000000000000001b <make_what_old+27>:	or     0x0(,%rdx,4),%eax
0x0000000000000022 <make_what_old+34>:	mov    %edi,%edx
0x0000000000000024 <make_what_old+36>:	and    $0x2,%edx
0x0000000000000027 <make_what_old+39>:	add    %edx,%edx
0x0000000000000029 <make_what_old+41>:	movslq %edx,%rdx
0x000000000000002c <make_what_old+44>:	or     %esi,%eax
0x000000000000002e <make_what_old+46>:	or     0x0(,%rdx,4),%eax
0x0000000000000035 <make_what_old+53>:	mov    %edi,%edx
0x0000000000000037 <make_what_old+55>:	and    $0x20,%edx
0x000000000000003a <make_what_old+58>:	and    $0x40,%edi
0x000000000000003d <make_what_old+61>:	sar    $0x2,%edx
0x0000000000000040 <make_what_old+64>:	sar    $0x2,%edi
0x0000000000000043 <make_what_old+67>:	movslq %edx,%rdx
0x0000000000000046 <make_what_old+70>:	movslq %edi,%rdi
0x0000000000000049 <make_what_old+73>:	or     0x0(,%rdx,4),%eax
0x0000000000000050 <make_what_old+80>:	or     0x0(,%rdi,4),%eax
0x0000000000000057 <make_what_old+87>:	leaveq 
0x0000000000000058 <make_what_old+88>:	retq   
End of assembler dump.
(gdb) disass make_what_new
Dump of assembler code for function make_what_new:
0x0000000000000059 <make_what_new+0>:	mov    %edi,%eax
0x000000000000005b <make_what_new+2>:	mov    %edi,%edx
0x000000000000005d <make_what_new+4>:	push   %rbp
0x000000000000005e <make_what_new+5>:	and    $0x4,%eax
0x0000000000000061 <make_what_new+8>:	and    $0x10,%edx
0x0000000000000064 <make_what_new+11>:	shl    $0xf,%edx
0x0000000000000067 <make_what_new+14>:	shl    $0x10,%eax
0x000000000000006a <make_what_new+17>:	mov    %rsp,%rbp
0x000000000000006d <make_what_new+20>:	or     %edx,%eax
0x000000000000006f <make_what_new+22>:	mov    %edi,%edx
0x0000000000000071 <make_what_new+24>:	and    $0x2,%edx
0x0000000000000074 <make_what_new+27>:	or     %esi,%eax
0x0000000000000076 <make_what_new+29>:	shl    $0x1a,%edx
0x0000000000000079 <make_what_new+32>:	leaveq 
0x000000000000007a <make_what_new+33>:	or     %edx,%eax
0x000000000000007c <make_what_new+35>:	mov    %edi,%edx
0x000000000000007e <make_what_new+37>:	and    $0x40,%edi
0x0000000000000081 <make_what_new+40>:	and    $0x20,%edx
0x0000000000000084 <make_what_new+43>:	shl    $0x17,%edi
0x0000000000000087 <make_what_new+46>:	shl    $0x17,%edx
0x000000000000008a <make_what_new+49>:	or     %edx,%eax
0x000000000000008c <make_what_new+51>:	or     %edi,%eax
0x000000000000008e <make_what_new+53>:	retq   
End of assembler dump.

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@intel.com                              Intel Corporation