digitalmars.D.bugs - [Issue 1149] New: Optimizer: obsolete array length loads, common subexpr. elimin. not working
- d-bugmail puremagic.com (49/49) Apr 15 2007 http://d.puremagic.com/issues/show_bug.cgi?id=1149
- d-bugmail puremagic.com (15/15) Feb 20 2012 http://d.puremagic.com/issues/show_bug.cgi?id=1149
- d-bugmail puremagic.com (9/9) Feb 22 2012 http://d.puremagic.com/issues/show_bug.cgi?id=1149
- d-bugmail puremagic.com (104/104) Feb 22 2012 http://d.puremagic.com/issues/show_bug.cgi?id=1149
- d-bugmail puremagic.com (9/14) Feb 22 2012 http://d.puremagic.com/issues/show_bug.cgi?id=1149
- d-bugmail puremagic.com (16/18) Feb 22 2012 http://d.puremagic.com/issues/show_bug.cgi?id=1149
- d-bugmail puremagic.com (13/31) Feb 22 2012 http://d.puremagic.com/issues/show_bug.cgi?id=1149
- d-bugmail puremagic.com (9/9) Feb 23 2012 http://d.puremagic.com/issues/show_bug.cgi?id=1149
- d-bugmail puremagic.com (33/33) Feb 23 2012 http://d.puremagic.com/issues/show_bug.cgi?id=1149
- d-bugmail puremagic.com (7/9) Feb 23 2012 http://d.puremagic.com/issues/show_bug.cgi?id=1149
http://d.puremagic.com/issues/show_bug.cgi?id=1149
Summary: Optimizer: obsolete array length loads, common subexpr.
elimin. not working
Product: D
Version: 1.012
Platform: PC
OS/Version: Windows
Status: NEW
Severity: normal
Priority: P2
Component: DMD
AssignedTo: bugzilla digitalmars.com
ReportedBy: jascha mainia.de
consider the following code:
void main()
{
uint[] arr;
arr.length = 4;
arr[0] = 1;
arr[1] = 1;
arr[2] = 1;
arr[3] = 1;
}
for the 4 assignments, "dmd -O -inline" generates
mov ECX,1
mov EDX,010h[ESP]
mov EAX,0Ch[ESP]
mov [EDX],ECX
mov EDX,010h[ESP]
mov EAX,0Ch[ESP]
mov 4[EDX],ECX
mov EDX,010h[ESP]
mov EAX,0Ch[ESP]
mov 8[EDX],ECX
mov EDX,010h[ESP]
mov EAX,0Ch[ESP]
mov 0Ch[EDX],ECX
instead of
mov ECX,1
mov EDX,010h[ESP]
mov [EDX],ECX
mov 4[EDX],ECX
mov 8[EDX],ECX
mov 0Ch[EDX],ECX
- the length of the array is always loaded, even if it's not used
- the array pointer is loaded multiple times into the same register
the common subexpression elimination appears to be working for the value in
ECX, but not for the pointer in EDX.
--
Apr 15 2007
d-bugmail puremagic.com
http://d.puremagic.com/issues/show_bug.cgi?id=1149
yebblies <yebblies gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |pull
CC| |yebblies gmail.com
Version|1.012 |D1 & D2
AssignedTo|nobody puremagic.com |yebblies gmail.com
https://github.com/D-Programming-Language/dmd/pull/749
This makes the code generated for arrays identical to the code for pointers.
The pointer is still reloaded before every assignment.
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Feb 20 2012
http://d.puremagic.com/issues/show_bug.cgi?id=1149 Commit pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/a999486f9bb0b6ca2eeff1964b8f9c90b8841867 Improve codegen for OPmsw -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Feb 22 2012
http://d.puremagic.com/issues/show_bug.cgi?id=1149
bearophile_hugs eml.cc changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |bearophile_hugs eml.cc
With the test code, this is the X86 asm I was seeing before this patch (-O
-release -inline):
__Dmain comdat
L0: sub ESP,0Ch
lea EAX,[ESP]
mov ECX,offset FLAT:_D11TypeInfo_Ak6__initZ
mov [ESP],0
mov dword ptr 4[ESP],0
push EAX
push 4
push ECX
call near ptr __d_arraysetlengthT
mov ECX,010h[ESP]
mov EDX,1
mov EAX,0Ch[ESP]
mov [ECX],EDX
mov ECX,010h[ESP]
mov EAX,0Ch[ESP]
mov 4[ECX],EDX
mov ECX,010h[ESP]
mov EAX,0Ch[ESP]
mov 8[ECX],EDX
mov ECX,010h[ESP]
mov EAX,0Ch[ESP]
mov 0Ch[ECX],EDX
add ESP,0Ch
add ESP,0Ch
xor EAX,EAX
ret
-----------------------------
After the patch:
__Dmain comdat
L0: sub ESP,0Ch
lea EAX,[ESP]
mov ECX,offset FLAT:_D11TypeInfo_Ak6__initZ
mov [ESP],0
mov dword ptr 4[ESP],0
push EAX
push 4
push ECX
call near ptr __d_arraysetlengthT
mov ECX,010h[ESP]
mov EDX,1
mov EAX,0Ch[ESP]
mov [ECX],EDX
mov ECX,010h[ESP]
mov EAX,0Ch[ESP]
mov 4[ECX],EDX
mov ECX,010h[ESP]
mov EAX,0Ch[ESP]
mov 8[ECX],EDX
mov ECX,010h[ESP]
mov EAX,0Ch[ESP]
mov 0Ch[ECX],EDX
add ESP,0Ch
add ESP,0Ch
xor EAX,EAX
ret
--------------------------------
objectdump after the patch, on a 64 bit systems (courtesy of q66 on IRC #D),
compiled with -release:
0000000000000000 <_Dmain>:
0: 55 push %rbp
1: 48 8b ec mov %rsp,%rbp
4: 48 83 ec 18 sub $0x18,%rsp
8: 53 push %rbx
9: 48 c7 45 f0 00 00 00 movq $0x0,-0x10(%rbp)
10: 00
11: 48 c7 45 f8 00 00 00 movq $0x0,-0x8(%rbp)
18: 00
19: 48 8d 55 f0 lea -0x10(%rbp),%rdx
1d: 48 be 04 00 00 00 00 mov $0x4,%rsi
24: 00 00 00
27: 48 bf 00 00 00 00 00 mov $0x0,%rdi
2e: 00 00 00
31: e8 00 00 00 00 callq 36 <_Dmain+0x36>
36: b8 01 00 00 00 mov $0x1,%eax
3b: 48 8b 55 f8 mov -0x8(%rbp),%rdx
3f: 48 8b 5d f0 mov -0x10(%rbp),%rbx
43: 89 02 mov %eax,(%rdx)
45: 48 8b 55 f8 mov -0x8(%rbp),%rdx
49: 48 8b 5d f0 mov -0x10(%rbp),%rbx
4d: 89 42 04 mov %eax,0x4(%rdx)
50: 48 8b 55 f8 mov -0x8(%rbp),%rdx
54: 48 8b 5d f0 mov -0x10(%rbp),%rbx
58: 89 42 08 mov %eax,0x8(%rdx)
5b: 48 8b 55 f8 mov -0x8(%rbp),%rdx
5f: 48 8b 5d f0 mov -0x10(%rbp),%rbx
63: 89 42 0c mov %eax,0xc(%rdx)
66: 31 c0 xor %eax,%eax
68: 5b pop %rbx
69: c9 leaveq
6a: c3 retq
--------------------------------
So is this patch working?
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Feb 22 2012
http://d.puremagic.com/issues/show_bug.cgi?id=1149With the test code, this is the X86 asm I was seeing before this patch (-O -release -inline):[snip]So is this patch working?Oops. I tried to disable it for floating point and ended up disabling it for all non-integers. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Feb 22 2012
http://d.puremagic.com/issues/show_bug.cgi?id=1149Oops. I tried to disable it for floating point and ended up disabling it for all non-integers.I have tried it with this code: void main() { int[] arr; arr.length = 4; arr[0] = 1; arr[1] = 1; arr[2] = 1; arr[3] = 1; } And I am seeing something similar to the uint[] case. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Feb 22 2012
http://d.puremagic.com/issues/show_bug.cgi?id=1149Yeah, the optimization in my patch is effectively disabled. I changed it to integer-only because it was crashing in some floating point code - but the most significant word of an array isn't an integer, it's a pointer. I've tracked to codegen down, it seems like 'fnstsw ax' destroys eax and it never gets restored. Without the optimization loading the pointer into eax never gets picked up as a cse and removed in the first place. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------Oops. I tried to disable it for floating point and ended up disabling it for all non-integers.I have tried it with this code: void main() { int[] arr; arr.length = 4; arr[0] = 1; arr[1] = 1; arr[2] = 1; arr[3] = 1; } And I am seeing something similar to the uint[] case.
Feb 22 2012
http://d.puremagic.com/issues/show_bug.cgi?id=1149 Commit pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/1d1bc367c131144e764d9fb81c36651407e3337d Fix OPmsw codegen -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Feb 23 2012
http://d.puremagic.com/issues/show_bug.cgi?id=1149
Better:
__Dmain comdat
L0: sub ESP,0Ch
mov ECX,offset FLAT:_D11TypeInfo_Ak6__initZ
push EBX
push ESI
lea EAX,8[ESP]
mov dword ptr 8[ESP],0
mov dword ptr 0Ch[ESP],0
push EAX
push 4
push ECX
call near ptr __d_arraysetlengthT
mov EBX,018h[ESP]
mov EDX,1
mov [EBX],EDX
mov ESI,018h[ESP]
mov 4[ESI],EDX
mov EAX,018h[ESP]
mov 8[EAX],EDX
mov ECX,018h[ESP]
xor EAX,EAX
mov 0Ch[ECX],EDX
add ESP,0Ch
pop ESI
pop EBX
add ESP,0Ch
ret
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Feb 23 2012
http://d.puremagic.com/issues/show_bug.cgi?id=1149Better:Yeah. I have no idea why it's using so many registers though. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Feb 23 2012