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203 Commits

Author SHA1 Message Date
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. 
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. 
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. 
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. 
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. 
llvm-svn: 119920
 2010-11-21 06:10:27 +00:00
Chris Lattner
b3eff154cd add a note 
llvm-svn: 118806
 2010-11-11 18:23:57 +00:00
Chris Lattner
3514fa6b11 add pr# 
llvm-svn: 118797
 2010-11-11 17:17:56 +00:00
Chris Lattner
d7d7d5717b add a case we fail to devirt. 
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. 
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 
(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-- 
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 
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. 
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. 
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. 
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