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291 Commits

Author SHA1 Message Date
Benjamin Kramer 2b76c66fd6 Add constant folding for strspn and strcspn to SimplifyLibCalls. 
llvm-svn: 115116
 2010-09-30 00:58:35 +00:00
Chris Lattner 011f146419 idiom recognition should catch this. 
llvm-svn: 114304
 2010-09-19 00:37:34 +00:00
Nick Lewycky bb10e90487 Add optimization to Target/README.txt. 
llvm-svn: 110543
 2010-08-08 07:04:25 +00:00
Benjamin Kramer 2321e6a4d4 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 c8f595212f Minor amendment to switch-lowering improvement. 
llvm-svn: 107569
 2010-07-03 08:43:32 +00:00
Eli Friedman 836fdbc85b Note switch-lowering inefficiency. 
llvm-svn: 107565
 2010-07-03 07:38:12 +00:00
Eric Christopher e34471bb31 Add another bswap idiom that isn't matched. 
llvm-svn: 107213
 2010-06-29 22:22:22 +00:00
Benjamin Kramer 41476410c9 TODO-- 
llvm-svn: 106102
 2010-06-16 15:47:00 +00:00
Eli Friedman e17e4aea2a Add README entry; based on testcase from Bill Hart. 
llvm-svn: 105878
 2010-06-12 05:54:27 +00:00
Chris Lattner 4dc833c607 add a note 
llvm-svn: 104404
 2010-05-21 23:16:21 +00:00
Dan Gohman 73c8145505 Add a README entry. 
llvm-svn: 102906
 2010-05-03 14:31:00 +00:00
Chris Lattner cfc921cd2a add a note 
llvm-svn: 101581
 2010-04-16 23:52:30 +00:00
Chris Lattner 4041ab6e00 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 1f6689a8ba move PR6576 here. 
llvm-svn: 98194
 2010-03-10 21:42:42 +00:00
Chris Lattner 187242b3ab move PR6212 to this file. 
llvm-svn: 95624
 2010-02-09 00:11:10 +00:00
Eli Friedman 0de0b3677a Remove a completed item, add a couple new ones. 
llvm-svn: 94945
 2010-01-31 04:55:32 +00:00
Bob Wilson 7c42b9d51e 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 e3a68d1063 reassociate should do this. 
llvm-svn: 94374
 2010-01-24 20:17:09 +00:00
Chris Lattner 7e3f8b60d6 add a note. 
llvm-svn: 94373
 2010-01-24 20:01:41 +00:00
Chris Lattner 249da5cb73 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 082da53f9a 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 9ed49c5c8f Add some potentially interesting transformations to README. 
llvm-svn: 93797
 2010-01-18 22:36:59 +00:00
Duncan Sands c8493da5b1 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 78376ad7e1 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 2d91231d82 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 39f18e545e 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 71cf7c256f 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 96cf7f42b0 More info on this transformation. 
llvm-svn: 91230
 2009-12-12 23:23:43 +00:00
Eli Friedman 8eada9f580 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 f05330a5c8 expand note. 
llvm-svn: 90429
 2009-12-03 07:43:46 +00:00
Chris Lattner d1e4ee3c2b add a note 
llvm-svn: 90428
 2009-12-03 07:41:54 +00:00
Chris Lattner 58ccf88c36 update and consolidate the load pre notes. 
llvm-svn: 90050
 2009-11-29 02:19:52 +00:00
Chris Lattner 83a4a9868f add a deadargelim note. 
llvm-svn: 90009
 2009-11-27 17:12:30 +00:00
Chris Lattner ca9e0e83b3 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 cc6d29286c this (and probably several others) are now done. 
llvm-svn: 89982
 2009-11-27 00:35:04 +00:00
Chris Lattner 9bd2136ca3 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 29bc8a91d3 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 12dacdd359 teach basicaa that A[i] != A[i+1]. 
llvm-svn: 89951
 2009-11-26 16:18:10 +00:00
Chris Lattner 8e09ad6f3c update some notes slightly 
llvm-svn: 89913
 2009-11-26 01:51:18 +00:00
Nick Lewycky ef4ea9a2a9 Add a complex missed optimization opportunity I came across while investigating 
bug 5438.

llvm-svn: 88855
 2009-11-15 17:51:23 +00:00
Chris Lattner 7a09964e81 another const prop failure. 
llvm-svn: 86848
 2009-11-11 17:54:02 +00:00
Chris Lattner 539bdf0487 add a note 
llvm-svn: 86847
 2009-11-11 17:51:27 +00:00
Chris Lattner 0169fd7c62 add a note 
llvm-svn: 86756
 2009-11-10 23:47:45 +00:00
Chris Lattner 8ff26038ef I did this a week or two ago 
llvm-svn: 86754
 2009-11-10 23:40:49 +00:00
Nick Lewycky b9397262b7 Improve tail call elimination to handle the switch statement. 
llvm-svn: 86403
 2009-11-07 21:10:15 +00:00
Chris Lattner 06c26d982e add a note from PR5313 
llvm-svn: 86146
 2009-11-05 18:19:19 +00:00
Bill Wendling 2e5198ff09 Add new note. 
llvm-svn: 85341
 2009-10-27 23:30:07 +00:00
Bill Wendling fd2730ee8c Move and clarify note. 
llvm-svn: 85334
 2009-10-27 22:48:31 +00:00
Chris Lattner 13b8b56dd4 this is done. 
llvm-svn: 85041
 2009-10-25 06:17:51 +00:00
Chris Lattner 851193b873 some stuff is done, we still have constantexpr simplification to do. 
llvm-svn: 84943
 2009-10-23 07:00:55 +00:00
Chris Lattner bc69313909 IPSCCP is missing stuff. 
llvm-svn: 84725
 2009-10-21 01:10:37 +00:00
Chris Lattner 61858787b1 add a note 
llvm-svn: 82442
 2009-09-21 06:04:07 +00:00
Chris Lattner 9858859fd6 one case handled, expanded another testcase inline. 
llvm-svn: 82427
 2009-09-21 02:53:57 +00:00
Chris Lattner fc2d846dc8 update an entry, delete an entry which has been fixed. 
llvm-svn: 82398
 2009-09-20 17:37:38 +00:00
Nick Lewycky 9b3ed87506 Peer through zext and sext to eliminate them when it is safe to do so. 
llvm-svn: 82389
 2009-09-20 07:31:25 +00:00
Chris Lattner dda095ec4a add PR# 
llvm-svn: 81770
 2009-09-14 16:49:26 +00:00
Dan Gohman 4ac2f639cd Transform -X/C to X/-C, implementing a README.txt entry. 
llvm-svn: 78812
 2009-08-12 16:37:02 +00:00
Eli Friedman 1e08ca7313 Remove a couple of already-implemented notes. 
llvm-svn: 76631
 2009-07-21 20:05:43 +00:00
Nick Lewycky 4e705e421c Move PR4517 to README.txt. 
llvm-svn: 75098
 2009-07-09 04:03:30 +00:00
Dan Gohman d76d71a291 Factor the code for collecting IV users out of LSR into an IVUsers class, 
and generalize it so that it can be used by IndVarSimplify. Implement the
base IndVarSimplify transformation code using IVUsers. This removes
TestOrigIVForWrap and associated code, as ScalarEvolution now has enough
builtin overflow detection and folding logic to handle all the same cases,
and more. Run "opt -iv-users -analyze -disable-output" on your favorite
loop for an example of what IVUsers does.

This lets IndVarSimplify eliminate IV casts and compute trip counts in
more cases. Also, this happens to finally fix the remaining testcases
in PR1301.

Now that IndVarSimplify is being more aggressive, it occasionally runs
into the problem where ScalarEvolutionExpander's code for avoiding
duplicate expansions makes it difficult to ensure that all expanded
instructions dominate all the instructions that will use them. As a
temporary measure, IndVarSimplify now uses a FixUsesBeforeDefs function
to fix up instructions inserted by SCEVExpander. Fortunately, this code
is contained, and can be easily removed once a more comprehensive
solution is available.

llvm-svn: 71535
 2009-05-12 02:17:14 +00:00
Dan Gohman 1dbb40f481 Fix two wording errors that Duncan spotted. 
llvm-svn: 71459
 2009-05-11 18:51:16 +00:00
Dan Gohman b0ddbbe7c4 LLVM has unaligned loads and stores now. 
llvm-svn: 71449
 2009-05-11 18:06:05 +00:00
Dan Gohman 7ee3a4371f Upgrade this example to new-style syntax. 
llvm-svn: 71447
 2009-05-11 18:04:52 +00:00
Chris Lattner 17a999efac remove some done things: we have nocapture and SROA is smarter. 
llvm-svn: 71443
 2009-05-11 17:41:40 +00:00
Chris Lattner 183a7ec027 add a note 
llvm-svn: 71442
 2009-05-11 17:36:33 +00:00
Eli Friedman f2d589fe24 Remove a completed optimization. Add a potential optimization I ran 
into.

llvm-svn: 71352
 2009-05-09 08:40:15 +00:00
Chris Lattner 356d974a93 add a note 
llvm-svn: 67953
 2009-03-28 19:26:55 +00:00
Nick Lewycky 5c10a3aa7f Add a totally synthetic situation I came up with while looking at a bug in 
related code.

llvm-svn: 65437
 2009-02-25 06:52:48 +00:00
Torok Edwin 87d5ca083b add note about sin 
llvm-svn: 65137
 2009-02-20 18:42:06 +00:00
Torok Edwin 3cedd4dc64 add note about possible GEP improvement with fields of size 0. 
llvm-svn: 62925
 2009-01-24 19:30:25 +00:00
Chris Lattner 705ac7082b add a note 
llvm-svn: 62760
 2009-01-22 07:16:03 +00:00
Dan Gohman 83d2e066c1 Add a README entry noticed while investigating PR3216. 
llvm-svn: 62558
 2009-01-20 01:07:33 +00:00
Chris Lattner 6c2ee50e28 add some more crazy strlen and memcpy stuff I noticed in spec. 
llvm-svn: 61918
 2009-01-08 07:34:55 +00:00
Chris Lattner 7cb3ae0505 add some notes about strlen craziness in eon. 
llvm-svn: 61917
 2009-01-08 06:52:57 +00:00
Chris Lattner a41422566b add a note 
llvm-svn: 61513
 2008-12-31 00:54:13 +00:00
Chris Lattner 8a35adf3a5 add some notes for simplifylibcalls optimizations 
llvm-svn: 61385
 2008-12-23 20:52:52 +00:00
Chris Lattner 5d196e64f1 add some more notes. 
llvm-svn: 61033
 2008-12-15 08:32:28 +00:00
Chris Lattner 81ee731852 Add a testcase for GCC PR 23455, which lpre handles now. Add some 
comments about why we're not getting other cases.

llvm-svn: 61032
 2008-12-15 07:49:24 +00:00
Chris Lattner 3c2c36b590 gvn now hoists this load out of the hot non-call path. 
llvm-svn: 61028
 2008-12-15 06:34:48 +00:00
Chris Lattner 56fe52e287 move an entry, add some notes, remove a completed item (IMPLICIT_DEF) 
llvm-svn: 60821
 2008-12-10 01:30:48 +00:00
Chris Lattner a163568c03 improve a note. 
llvm-svn: 60636
 2008-12-07 00:15:10 +00:00
Chris Lattner da93063acc some more PRE/GVN/DSE related notes. 
llvm-svn: 60633
 2008-12-06 22:52:12 +00:00
Chris Lattner 543d6c65fa some random notes. 
llvm-svn: 60624
 2008-12-06 19:28:22 +00:00
Chris Lattner 0cdc0bbb8a add a note 
llvm-svn: 60404
 2008-12-02 06:32:34 +00:00
Bill Wendling 85de4b35ca - Remove the buggy -X/C -> X/-C transform. This isn't valid when X isn't a 
constant. If X is a constant, then this is folded elsewhere.

- Added a note to Target/README.txt to indicate that we'd like to implement
  this when we're able.

llvm-svn: 60399
 2008-12-02 05:12:47 +00:00
Bill Wendling 5b902c5b1e Implement ((A|B)&1)|(B&-2) -> (A&1) | B transformation. This also takes care of 
permutations of this pattern.

llvm-svn: 60312
 2008-12-01 01:07:11 +00:00
Bill Wendling de89bc275c Add instruction combining for ((A&~B)|(~A&B)) -> A^B and all permutations. 
llvm-svn: 60291
 2008-11-30 13:52:49 +00:00
Bill Wendling 9eef421e12 Implement (A&((~A)|B)) -> A&B transformation in the instruction combiner. This 
takes care of all permutations of this pattern.

llvm-svn: 60290
 2008-11-30 13:08:13 +00:00
Eli Friedman e16c0ff1d3 Moving potential optimizations out of PR2330 into lib/Target/README.txt. 
Hopefully this isn't too much stuff to dump into this file.

llvm-svn: 60285
 2008-11-30 07:36:04 +00:00
Nick Lewycky edd5d3e4e9 Also update the README. 
llvm-svn: 60188
 2008-11-27 22:41:45 +00:00
Nick Lewycky b3dc4ad5b4 Add a synthetic missed optimization. 
llvm-svn: 60186
 2008-11-27 22:12:22 +00:00
Torok Edwin 33986d8f17 move the note to the correct README 
llvm-svn: 58104
 2008-10-24 19:23:07 +00:00
Torok Edwin fcaae54669 add note about va_arg code on x86 and x86-64 
llvm-svn: 58103
 2008-10-24 19:20:05 +00:00
Dan Gohman 209fc26462 This is now partly done. 
llvm-svn: 57734
 2008-10-17 21:39:27 +00:00
Chris Lattner 9b83197b76 move PR1941 here. 
llvm-svn: 57586
 2008-10-15 16:33:52 +00:00
Chris Lattner 6d275fd6e1 move PR1604 here. 
llvm-svn: 57582
 2008-10-15 16:06:03 +00:00
Chris Lattner 843dacc937 move PR1488 into this file. 
llvm-svn: 57579
 2008-10-15 16:02:15 +00:00
Chris Lattner 117792afec add a note 
llvm-svn: 57557
 2008-10-15 05:53:25 +00:00
Chris Lattner f9325e5f67 this case is matched now. 
llvm-svn: 57096
 2008-10-05 02:16:12 +00:00
Chris Lattner d7dd8b8aeb add a note 
llvm-svn: 54985
 2008-08-19 06:22:16 +00:00
Chris Lattner 113b336caa move some more stuff out of my email into readme.txt 
llvm-svn: 54603
 2008-08-10 01:14:08 +00:00
Chris Lattner 4afb010309 add a note 
llvm-svn: 54602
 2008-08-10 00:47:21 +00:00
Chris Lattner 8377c02308 Add a note. 
llvm-svn: 53535
 2008-07-14 00:19:59 +00:00
Nick Lewycky 035fe6f716 Peer through sext/zext when looking for not(cmp). 
llvm-svn: 51819
 2008-05-31 19:01:33 +00:00
Nick Lewycky 69a51cbd6d Yay us! Every one of these examples turns into icmp/zext/ret. 
llvm-svn: 51818
 2008-05-31 18:20:26 +00:00
Chris Lattner 1bafa6c886 trip count computation deficiency 
llvm-svn: 51222
 2008-05-17 15:37:38 +00:00
Nick Lewycky 9fb8908457 Moved from PR1570. 
llvm-svn: 48965
 2008-03-30 19:07:11 +00:00
Chris Lattner fd5fe2a83d add a note. 
llvm-svn: 48583
 2008-03-20 04:46:13 +00:00
Chris Lattner af8d3c6699 various rotate fun. 
llvm-svn: 48438
 2008-03-17 01:47:51 +00:00
Chris Lattner d51372aa96 another random note 
llvm-svn: 47831
 2008-03-02 19:29:42 +00:00
Chris Lattner 647c6642e7 Move pr717 to here. 
llvm-svn: 47803
 2008-03-02 02:51:40 +00:00
Chris Lattner 643dce1146 add a note 
llvm-svn: 47720
 2008-02-28 17:21:27 +00:00
Chris Lattner 765be8874d target-indep codegen memcpy lowering issue. 
llvm-svn: 47705
 2008-02-28 05:34:27 +00:00
Chris Lattner 6bb6a55f01 upgrade some tests. 
llvm-svn: 47280
 2008-02-18 18:46:39 +00:00
Nate Begeman 0fddc34485 Add a note 
llvm-svn: 47279
 2008-02-18 18:39:23 +00:00
Chris Lattner afb514a7b4 clarify a note 
llvm-svn: 45914
 2008-01-12 18:58:46 +00:00
Chris Lattner 87b0c13104 add some notes. 
llvm-svn: 45854
 2008-01-11 06:17:47 +00:00
Chris Lattner 1d07b65add add a note 
llvm-svn: 45837
 2008-01-10 18:25:41 +00:00
Chris Lattner 45e5032b1d add a note 
llvm-svn: 45766
 2008-01-09 00:17:57 +00:00
Chris Lattner 730d088be1 possible switch lowering improvement. 
llvm-svn: 45720
 2008-01-07 21:38:14 +00:00
Chris Lattner d7857eafd0 add a note 
llvm-svn: 45698
 2008-01-07 07:46:23 +00:00
Chris Lattner 4e6cbb2fe2 this is done. 
llvm-svn: 45408
 2007-12-29 19:38:02 +00:00
Chris Lattner 7cafd92aa9 expand note. 
llvm-svn: 45393
 2007-12-29 01:05:01 +00:00
Chris Lattner 9d53b611d1 add a note. 
llvm-svn: 45388
 2007-12-28 22:30:05 +00:00
Chris Lattner 180f0e9044 add a note 
llvm-svn: 45377
 2007-12-28 04:42:05 +00:00
Christopher Lamb 8b09a464b4 Fold certain additions through selects (and their compares) so as to eliminate subtractions. This code is often produced by the SMAX expansion in SCEV. 
This implements test/Transforms/InstCombine/2007-12-18-AddSelCmpSub.ll

llvm-svn: 45158
 2007-12-18 09:34:41 +00:00
Chris Lattner 52a9e40789 add a missed case. 
llvm-svn: 45141
 2007-12-18 01:19:18 +00:00
Chris Lattner 7c709a5d08 implement a readme entry, compiling the code into: 
_foo:
	movl	$12, %eax
	andl	4(%esp), %eax
	movl	_array(%eax), %eax
	ret

instead of:

_foo:
	movl	4(%esp), %eax
	shrl	$2, %eax
	andl	$3, %eax
	movl	_array(,%eax,4), %eax
	ret

As it turns out, this triggers all the time, in a wide variety of
situations, for example, I see diffs like this in various programs:

-       movl    8(%eax), %eax
-       shll    $2, %eax
-       andl    $1020, %eax
-       movl    (%esi,%eax), %eax
+       movzbl  8(%eax), %eax
+       movl    (%esi,%eax,4), %eax


-       shll    $2, %edx
-       andl    $1020, %edx
-       movl    (%edi,%edx), %edx
+       andl    $255, %edx
+       movl    (%edi,%edx,4), %edx

Unfortunately, I also see stuff like this, which can be fixed in the
X86 backend:

-       andl    $85, %ebx
-       addl    _bit_count(,%ebx,4), %ebp
+       shll    $2, %ebx
+       andl    $340, %ebx
+       addl    _bit_count(%ebx), %ebp

llvm-svn: 44656
 2007-12-06 07:33:36 +00:00
Chris Lattner 5e224c32f4 add a note 
llvm-svn: 44638
 2007-12-05 23:05:06 +00:00
Chris Lattner 4d4e9cdb62 add a note 
llvm-svn: 42573
 2007-10-03 06:10:59 +00:00
Chris Lattner 9958b82733 add a note 
llvm-svn: 36811
 2007-05-05 22:44:08 +00:00
Chris Lattner 2cca31f77f the mason example is implemented. Move some examples out of llvm/test, 
upgrade the syntax of some other examples.

llvm-svn: 36806
 2007-05-05 22:29:06 +00:00
Chris Lattner 43cab75914 add a bad case evan though of. 
llvm-svn: 35296
 2007-03-24 06:01:32 +00:00
Chris Lattner 9b3e2b4ad9 minor updates 
llvm-svn: 35143
 2007-03-18 22:41:33 +00:00
Nick Lewycky f764441977 This is implemented. We now generate: 
entry:
        icmp ugt i32 %x, 4              ; <i1>:0 [#uses=1]
        br i1 %0, label %cond_true, label %cond_false

cond_true:              ; preds = %entry
        %tmp1 = tail call i32 (...)* @bar( i32 12 )             ; <i32> [#uses=0]
        ret void

cond_false:             ; preds = %entry
        switch i32 %x, label %cond_true15 [
                 i32 4, label %cond_true3
                 i32 3, label %cond_true7
                 i32 2, label %cond_true11
                 i32 0, label %cond_false17
        ]

...

llvm-svn: 35142
 2007-03-18 14:37:20 +00:00
Reid Spencer 09575bac2e For PR1195: 
Change use of "packed" term to "vector" in comments, strings, variable
names, etc.

llvm-svn: 34300
 2007-02-15 03:39:18 +00:00
Chris Lattner 09a32e42bd add a note 
llvm-svn: 34249
 2007-02-13 21:44:43 +00:00
Chris Lattner 89e5813312 add a note: we need whole-function selectiondags :) 
llvm-svn: 33252
 2007-01-16 06:39:48 +00:00
Reid Spencer 266e42b312 For PR950: 
This patch removes the SetCC instructions and replaces them with the ICmp
and FCmp instructions. The SetCondInst instruction has been removed and
been replaced with ICmpInst and FCmpInst.

llvm-svn: 32751
 2006-12-23 06:05:41 +00:00
Chris Lattner feeb9c7be5 Evan implemented the machineinstr improvements. 
The rot example works if the type is cast to ubyte.

Move sroa examples together and upgrade them to HEAD syntax.

llvm-svn: 32423
 2006-12-11 00:44:03 +00:00
Chris Lattner 4d475f6e6e add a note 
llvm-svn: 32347
 2006-12-08 02:01:32 +00:00
Chris Lattner 0d67dde00a done 
llvm-svn: 32013
 2006-11-29 07:21:46 +00:00
Chris Lattner 6dc22332bf add a note 
llvm-svn: 31719
 2006-11-14 01:57:53 +00:00
Nick Lewycky 0df2ada9d4 Cute example from Chris Lattner. 
llvm-svn: 31696
 2006-11-13 00:23:28 +00:00
Chris Lattner 4e03cb1945 add a note about viterbi 
llvm-svn: 31612
 2006-11-10 00:23:26 +00:00
Chris Lattner 7e885005ba add a note 
llvm-svn: 31477
 2006-11-06 21:26:49 +00:00
Chris Lattner 2048373e71 add a note 
llvm-svn: 31429
 2006-11-03 22:27:39 +00:00
Reid Spencer 7e80b0b31e For PR950: 
Make necessary changes to support DIV -> [SUF]Div. This changes llvm to
have three division instructions: signed, unsigned, floating point. The
bytecode and assembler are bacwards compatible, however.

llvm-svn: 31195
 2006-10-26 06:15:43 +00:00
Chris Lattner f054003ba7 new bad case 
llvm-svn: 31156
 2006-10-24 16:12:47 +00:00
Chris Lattner 3cbd1604f8 add a note about a general improvement to the code generator 
llvm-svn: 30642
 2006-09-28 06:01:17 +00:00