Benjamin Kramer
8d7096e8ca
The srem -> urem transform is not safe for any divisor that's not a power of two.
...
E.g. -5 % 5 is 0 with srem and 1 with urem.
Also addresses Frits van Bommel's comments.
llvm-svn: 120049
2010-11-23 20:33:57 +00:00
Benjamin Kramer
c8e6037e7d
InstCombine: Reduce "X shift (A srem B)" to "X shift (A urem B)" iff B is positive.
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This allows to transform the rem in "1 << ((int)x % 8);" to an and.
llvm-svn: 120028
2010-11-23 18:52:42 +00:00
Benjamin Kramer
b5a2a81094
InstCombine: Implement X - A*-B -> X + A*B.
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llvm-svn: 119984
2010-11-22 20:31:27 +00:00
Benjamin Kramer
632a91cba5
Implement the "if (X == 6 || X == 4)" -> "if ((X|2) == 6)" optimization.
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This currently only catches the most basic case, a two-case switch, but can be
extended later.
llvm-svn: 119964
2010-11-22 09:45:38 +00:00
Chris Lattner
ed3b3d47f6
add some random notes.
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llvm-svn: 119925
2010-11-21 07:05:31 +00:00
Chris Lattner
908a01328c
optimize:
...
void a(int x) { if (((1<<x)&8)==0) b(); }
into "x != 3", which occurs over 100 times in 403.gcc but in no
other program in llvm-test.
llvm-svn: 119922
2010-11-21 06:44:42 +00:00
Chris Lattner
09bf382b8f
tail calls on x86 are implemented.
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llvm-svn: 119920
2010-11-21 06:10:27 +00:00
Chris Lattner
b3eff154cd
add a note
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llvm-svn: 118806
2010-11-11 18:23:57 +00:00
Chris Lattner
3514fa6b11
add pr#
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llvm-svn: 118797
2010-11-11 17:17:56 +00:00
Chris Lattner
d7d7d5717b
add a case we fail to devirt.
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llvm-svn: 118608
2010-11-09 19:37:28 +00:00
Duncan Sands
c9c7d54930
Fix a README item: when doing a comparison with the result
...
of a select instruction, see if doing the compare with the
true and false values of the select gives the same result.
If so, that can be used as the value of the comparison.
llvm-svn: 118378
2010-11-07 16:12:23 +00:00
Benjamin Kramer
16b841c233
Add a note.
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llvm-svn: 118337
2010-11-06 10:37:16 +00:00
Benjamin Kramer
2a44a539e2
Add constant folding for strspn and strcspn to SimplifyLibCalls.
...
llvm-svn: 115116
2010-09-30 00:58:35 +00:00
Chris Lattner
3203bf3688
idiom recognition should catch this.
...
llvm-svn: 114304
2010-09-19 00:37:34 +00:00
Nick Lewycky
3a15ba4d5e
Add optimization to Target/README.txt.
...
llvm-svn: 110543
2010-08-08 07:04:25 +00:00
Benjamin Kramer
27eb255a70
Teach instcombine to transform
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(X >s -1) ? C1 : C2 and (X <s 0) ? C2 : C1
into ((X >>s 31) & (C2 - C1)) + C1, avoiding the conditional.
This optimization could be extended to take non-const C1 and C2 but we better
stay conservative to avoid code size bloat for now.
for
int sel(int n) {
return n >= 0 ? 60 : 100;
}
we now generate
sarl $31, %edi
andl $40, %edi
leal 60(%rdi), %eax
instead of
testl %edi, %edi
movl $60, %ecx
movl $100, %eax
cmovnsl %ecx, %eax
llvm-svn: 107866
2010-07-08 11:39:10 +00:00
Eli Friedman
4cac2d90a2
Minor amendment to switch-lowering improvement.
...
llvm-svn: 107569
2010-07-03 08:43:32 +00:00
Eli Friedman
663bc3ce7e
Note switch-lowering inefficiency.
...
llvm-svn: 107565
2010-07-03 07:38:12 +00:00
Eric Christopher
4c54014a1e
Add another bswap idiom that isn't matched.
...
llvm-svn: 107213
2010-06-29 22:22:22 +00:00
Benjamin Kramer
01a44323f0
TODO--
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llvm-svn: 106102
2010-06-16 15:47:00 +00:00
Eli Friedman
b4ac3e405c
Add README entry; based on testcase from Bill Hart.
...
llvm-svn: 105878
2010-06-12 05:54:27 +00:00
Chris Lattner
d5c391bba6
add a note
...
llvm-svn: 104404
2010-05-21 23:16:21 +00:00
Dan Gohman
4f9dc00cec
Add a README entry.
...
llvm-svn: 102906
2010-05-03 14:31:00 +00:00
Chris Lattner
136547652d
add a note
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llvm-svn: 101581
2010-04-16 23:52:30 +00:00
Chris Lattner
3282f3d34f
Implement rdar://7860110 (also in target/readme.txt) narrowing
...
a load/or/and/store sequence into a narrower store when it is
safe. Daniel tells me that clang will start producing this sort
of thing with bitfields, and this does trigger a few dozen times
on 176.gcc produced by llvm-gcc even now.
This compiles code like CodeGen/X86/2009-05-28-DAGCombineCrash.ll
into:
movl %eax, 36(%rdi)
instead of:
movl $4294967295, %eax ## imm = 0xFFFFFFFF
andq 32(%rdi), %rax
shlq $32, %rcx
addq %rax, %rcx
movq %rcx, 32(%rdi)
and each of the testcases into a single store. Each of them used
to compile into craziness like this:
_test4:
movl $65535, %eax ## imm = 0xFFFF
andl (%rdi), %eax
shll $16, %esi
addl %eax, %esi
movl %esi, (%rdi)
ret
llvm-svn: 101343
2010-04-15 04:48:01 +00:00
Chris Lattner
d14ff9f87b
move PR6576 here.
...
llvm-svn: 98194
2010-03-10 21:42:42 +00:00
Chris Lattner
dbbd13f825
move PR6212 to this file.
...
llvm-svn: 95624
2010-02-09 00:11:10 +00:00
Eli Friedman
28884d637b
Remove a completed item, add a couple new ones.
...
llvm-svn: 94945
2010-01-31 04:55:32 +00:00
Bob Wilson
f897b7b37e
Improve isSafeToLoadUnconditionally to recognize that GEPs with constant
...
indices are safe if the result is known to be within the bounds of the
underlying object.
llvm-svn: 94829
2010-01-29 19:19:08 +00:00
Chris Lattner
82318209c4
reassociate should do this.
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llvm-svn: 94374
2010-01-24 20:17:09 +00:00
Chris Lattner
e328ab9a00
add a note.
...
llvm-svn: 94373
2010-01-24 20:01:41 +00:00
Chris Lattner
8909d5aca5
implement a simple instcombine xform that has been in the
...
readme forever.
llvm-svn: 94318
2010-01-23 18:49:30 +00:00
Chris Lattner
fdc6162f82
add some notes, making posix-memalign be nocapture would be an easy improvement.
...
llvm-svn: 94312
2010-01-23 17:59:23 +00:00
Eli Friedman
0aade63ca6
Add some potentially interesting transformations to README.
...
llvm-svn: 93797
2010-01-18 22:36:59 +00:00
Duncan Sands
de0adbdf25
Fix a README item: have functionattrs look through selects and
...
phi nodes when deciding which pointers point to local memory.
I actually checked long ago how useful this is, and it isn't
very: it hardly ever fires in the testsuite, but since Chris
wants it here it is!
llvm-svn: 92836
2010-01-06 15:37:47 +00:00
Duncan Sands
4ef1119d94
Partially address a README by having functionattrs consider calls to
...
memcpy, memset and other intrinsics that only access their arguments
to be readnone if the intrinsic's arguments all point to local memory.
This improves the testcase in the README to readonly, but it could in
theory be made readnone, however this would involve more sophisticated
analysis that looks through the memcpy.
llvm-svn: 92829
2010-01-06 08:45:52 +00:00
Chris Lattner
ce3f5f3448
implement an instcombine xform needed by clang's codegen
...
on the example in PR4216. This doesn't trigger in the testsuite,
so I'd really appreciate someone scrutinizing the logic for
correctness.
llvm-svn: 92458
2010-01-04 06:03:59 +00:00
Chris Lattner
44298d184a
Teach codegen to lower llvm.powi to an efficient (but not optimal)
...
multiply sequence when the power is a constant integer. Before, our
codegen for std::pow(.., int) always turned into a libcall, which was
really inefficient.
This should also make many gfortran programs happier I'd imagine.
llvm-svn: 92388
2010-01-01 03:32:16 +00:00
Chris Lattner
0ea2e3d444
update this. To take the next step, llvm.powi should be generalized to work
...
on integers as well and codegen should lower them to branch trees.
llvm-svn: 92382
2010-01-01 01:29:26 +00:00
Eli Friedman
392adbdd7d
More info on this transformation.
...
llvm-svn: 91230
2009-12-12 23:23:43 +00:00
Eli Friedman
38a7d3b32e
Remove some stuff that's already implemented. Also, remove the note about
...
merging x >u 5 and x <s 20 because it's impossible to implement.
llvm-svn: 91228
2009-12-12 21:41:48 +00:00
Chris Lattner
b46655e25c
expand note.
...
llvm-svn: 90429
2009-12-03 07:43:46 +00:00
Chris Lattner
6b86618a2b
add a note
...
llvm-svn: 90428
2009-12-03 07:41:54 +00:00
Chris Lattner
40d74cea6b
update and consolidate the load pre notes.
...
llvm-svn: 90050
2009-11-29 02:19:52 +00:00
Chris Lattner
0df78ea645
add a deadargelim note.
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llvm-svn: 90009
2009-11-27 17:12:30 +00:00
Chris Lattner
c0b92ff385
This testcase is actually only partially redundant, and requires
...
the FIXME I added yesterday to be implemented.
llvm-svn: 90008
2009-11-27 16:53:57 +00:00
Chris Lattner
225a88f4ab
this (and probably several others) are now done.
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llvm-svn: 89982
2009-11-27 00:35:04 +00:00
Chris Lattner
4824ebfded
Teach memdep to phi translate bitcasts. This allows us to compile
...
the example in GCC PR16799 to:
LBB1_2: ## %bb1
movl %eax, %eax
subq %rax, %rdi
movq %rdi, (%rcx)
movl (%rdi), %eax
testl %eax, %eax
je LBB1_2
instead of:
LBB1_2: ## %bb1
movl (%rdi), %ecx
subq %rcx, %rdi
movq %rdi, (%rax)
cmpl $0, (%rdi)
je LBB1_2
llvm-svn: 89978
2009-11-26 23:41:07 +00:00
Chris Lattner
9c88c96b3f
Teach basicaa that x|c == x+c when the c bits of x are clear. This
...
allows us to compile the example in readme.txt into:
LBB1_1: ## %bb
movl 4(%rdx,%rax), %ecx
movl %ecx, %esi
imull (%rdx,%rax), %esi
imull %esi, %ecx
movl %esi, 8(%rdx,%rax)
imull %ecx, %esi
movl %ecx, 12(%rdx,%rax)
movl %esi, 16(%rdx,%rax)
imull %ecx, %esi
movl %esi, 20(%rdx,%rax)
addq $16, %rax
cmpq $4000, %rax
jne LBB1_1
instead of:
LBB1_1:
movl (%rdx,%rax), %ecx
imull 4(%rdx,%rax), %ecx
movl %ecx, 8(%rdx,%rax)
imull 4(%rdx,%rax), %ecx
movl %ecx, 12(%rdx,%rax)
imull 8(%rdx,%rax), %ecx
movl %ecx, 16(%rdx,%rax)
imull 12(%rdx,%rax), %ecx
movl %ecx, 20(%rdx,%rax)
addq $16, %rax
cmpq $4000, %rax
jne LBB1_1
GCC (4.2) doesn't seem to be able to eliminate the loads in this
testcase either, it generates:
L2:
movl (%rdx), %eax
imull 4(%rdx), %eax
movl %eax, 8(%rdx)
imull 4(%rdx), %eax
movl %eax, 12(%rdx)
imull 8(%rdx), %eax
movl %eax, 16(%rdx)
imull 12(%rdx), %eax
movl %eax, 20(%rdx)
addl $4, %ecx
addq $16, %rdx
cmpl $1002, %ecx
jne L2
llvm-svn: 89952
2009-11-26 16:26:43 +00:00
Chris Lattner
677b93d4c8
teach basicaa that A[i] != A[i+1].
...
llvm-svn: 89951
2009-11-26 16:18:10 +00:00