digitalmars.D.bugs - [Issue 9991] New: Optimizer Doesn't Enregister Static Array Elements With Compile-Time Constant Index
- d-bugmail puremagic.com (114/114) Apr 25 2013 http://d.puremagic.com/issues/show_bug.cgi?id=9991
- d-bugmail puremagic.com (12/12) Apr 25 2013 http://d.puremagic.com/issues/show_bug.cgi?id=9991
- d-bugmail puremagic.com (11/13) Apr 25 2013 http://d.puremagic.com/issues/show_bug.cgi?id=9991
- d-bugmail puremagic.com (7/8) Apr 25 2013 http://d.puremagic.com/issues/show_bug.cgi?id=9991
- d-bugmail puremagic.com (70/72) Jun 14 2013 http://d.puremagic.com/issues/show_bug.cgi?id=9991
http://d.puremagic.com/issues/show_bug.cgi?id=9991
Summary: Optimizer Doesn't Enregister Static Array Elements
With Compile-Time Constant Index
Product: D
Version: D1 & D2
Platform: All
OS/Version: All
Status: NEW
Keywords: performance
Severity: normal
Priority: P2
Component: DMD
AssignedTo: nobody puremagic.com
ReportedBy: dsimcha yahoo.com
Can't static array elements where the index is known at compile time be treated
just like regular stack variables? GDC seems to treat them as such.
D Source code below. I'd expect these two implementations to compile to the
exact same ASM. In GDC, the main loops do, though the pre-loop setup stuff
does compile differently for reasons I don't understand.
int sum1(const int[] arr) {
auto end = arr.ptr + arr.length - 3;
int[4] sums;
for(auto cur = arr.ptr; cur < end; cur += 4) {
sums[0] += cur[0];
sums[1] += cur[1];
sums[2] += cur[2];
sums[3] += cur[3];
}
return sums[0] + sums[1] + sums[2] + sums[3];
}
int sum2(const int[] arr) {
auto end = arr.ptr + arr.length - 3;
int sum0 = 0, sum1 = 0, sum2 = 0, sum3 = 0;
for(auto cur = arr.ptr; cur < end; cur += 4) {
sum0 += cur[0];
sum1 += cur[1];
sum2 += cur[2];
sum3 += cur[3];
}
return sum0 + sum1 + sum2 + sum3;
}
ASM:
_D5test34sum1FxAiZi:
push RBP
mov RBP,RSP
sub RSP,020h
push RBX
lea RAX,-020h[RBP]
xor RCX,RCX
mov [RAX],RCX
mov 8[RAX],RCX
mov R8,RSI
mov RDX,RSI
mov R9,RDI
lea R9,0FFFFFFF4h[R9*4][RDX]
cmp RDX,R9
jae L51
L2D: mov EBX,[R8]
add -020h[RBP],EBX
mov ESI,4[R8]
add -01Ch[RBP],ESI
mov EAX,8[R8]
add -018h[RBP],EAX
mov ECX,0Ch[R8]
add -014h[RBP],ECX
add R8,010h
cmp R8,R9
jb L2D
L51: mov EAX,-020h[RBP]
add EAX,-01Ch[RBP]
add EAX,-018h[RBP]
add EAX,-014h[RBP]
pop RBX
mov RSP,RBP
pop RBP
ret
nop
_D5test34sum2FxAiZi:
push RBP
mov RBP,RSP
sub RSP,010h
push RBX
push R12
push R13
xor R9D,R9D
xor R11D,R11D
xor EBX,EBX
xor R12D,R12D
mov R8,RSI
mov RAX,RSI
mov R13,RDI
lea R13,0FFFFFFF4h[R13*4][RAX]
cmp RAX,R13
jae L46
L2E: add R9D,[R8]
add R11D,4[R8]
add EBX,8[R8]
add R12D,0Ch[R8]
add R8,010h
cmp R8,R13
jb L2E
L46: lea EAX,[R11][R9]
add EAX,EBX
add EAX,R12D
pop R13
pop R12
pop RBX
mov RSP,RBP
pop RBP
ret
--
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Apr 25 2013
d-bugmail puremagic.com
http://d.puremagic.com/issues/show_bug.cgi?id=9991
Walter Bright <bugzilla digitalmars.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |bugzilla digitalmars.com
Severity|normal |enhancement
12:41:56 PDT ---
The optimizer currently does not enregister variables that don't fit into
registers. It could be enhanced to do it.
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http://d.puremagic.com/issues/show_bug.cgi?id=9991
timon.gehr gmx.ch changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |timon.gehr gmx.ch
The optimizer currently does not enregister variables that don't fit into
registers. It could be enhanced to do it.
ints definitely fit into registers.
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http://d.puremagic.com/issues/show_bug.cgi?id=9991 13:44:14 PDT ---ints definitely fit into registers.sums is one variable, not 4. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Apr 25 2013
http://d.puremagic.com/issues/show_bug.cgi?id=9991
bearophile_hugs eml.cc changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |bearophile_hugs eml.cc
In GDC, the main loops do, though the pre-loop setup stuff
does compile differently for reasons I don't understand.
ldc2 compiles them to the same asm (-release -profile-verifier-noassert -O5
-output-s):
__D4test4sum1FxAiZi:
pushl %ebx
pushl %edi
pushl %esi
movl 16(%esp), %eax
movl 20(%esp), %esi
leal -12(%esi,%eax,4), %ebx
xorl %ecx, %ecx
xorl %edx, %edx
xorl %edi, %edi
xorl %eax, %eax
jmp LBB0_2
.align 16, 0x90
LBB0_1:
addl 12(%esi), %eax
addl 8(%esi), %edi
addl 4(%esi), %edx
addl (%esi), %ecx
addl $16, %esi
LBB0_2:
cmpl %ebx, %esi
jb LBB0_1
addl %edi, %eax
addl %edx, %eax
addl %ecx, %eax
popl %esi
popl %edi
popl %ebx
ret $8
__D4test4sum2FxAiZi:
pushl %ebx
pushl %edi
pushl %esi
movl 16(%esp), %eax
movl 20(%esp), %esi
leal -12(%esi,%eax,4), %ebx
xorl %ecx, %ecx
xorl %edx, %edx
xorl %edi, %edi
xorl %eax, %eax
jmp LBB1_2
.align 16, 0x90
LBB1_1:
addl 12(%esi), %ecx
addl 8(%esi), %edx
addl 4(%esi), %edi
addl (%esi), %eax
addl $16, %esi
LBB1_2:
cmpl %ebx, %esi
jb LBB1_1
addl %edi, %eax
addl %edx, %eax
addl %ecx, %eax
popl %esi
popl %edi
popl %ebx
ret $8
--
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Jun 14 2013