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Commit Graph

264 Commits

Author SHA1 Message Date
Benjamin Kramer
12ea727553 Add a note.
llvm-svn: 128286
2011-03-25 17:32:40 +00:00
Eli Friedman
f9d5010081 A bit more analysis of a memset-related README entry.
llvm-svn: 128107
2011-03-22 20:49:53 +00:00
Eli Friedman
0da0b4aed0 This README entry was fixed recently.
llvm-svn: 127982
2011-03-21 01:33:03 +00:00
Chris Lattner
871d62dc5b add a note
llvm-svn: 126719
2011-03-01 00:24:51 +00:00
Benjamin Kramer
412ffed4f0 Add some DAGCombines for (adde 0, 0, glue), which are useful to optimize legalized code for large integer arithmetic.
1. Inform users of ADDEs with two 0 operands that it never sets carry
2. Fold other ADDs or ADDCs into the ADDE if possible

It would be neat if we could do the same thing for SETCC+ADD eventually, but we can't do that in target independent code.

llvm-svn: 126557
2011-02-26 22:48:07 +00:00
Chris Lattner
c373140c8b add a missed loop deletion case.
llvm-svn: 126103
2011-02-21 02:13:39 +00:00
Chris Lattner
8760c28fe1 add an idiom that loop idiom could theoretically catch.
llvm-svn: 126101
2011-02-21 01:33:38 +00:00
Duncan Sands
e0ece264ba This has been implemented.
llvm-svn: 125738
2011-02-17 08:16:56 +00:00
Chris Lattner
035876162f add some notes on compares + binops. Remove redundant entries.
llvm-svn: 125702
2011-02-17 01:43:46 +00:00
Chris Lattner
9f4e529571 Add a few missed xforms from GCC PR14753
llvm-svn: 125681
2011-02-16 19:16:34 +00:00
Eli Friedman
b409f8da64 Remove outdated README entry.
llvm-svn: 125660
2011-02-16 07:41:19 +00:00
Eli Friedman
5f848d70fa Remove outdated README entry.
llvm-svn: 125659
2011-02-16 07:18:18 +00:00
Eli Friedman
30a64ae1b9 Update README entry.
llvm-svn: 125658
2011-02-16 07:17:44 +00:00
Anders Carlsson
61f2126479 Remove a virtual inheritance case that clang can devirtualize fully now.
llvm-svn: 124989
2011-02-06 20:16:49 +00:00
Benjamin Kramer
b739613711 SimplifyCFG: Turn switches into sub+icmp+branch if possible.
This makes the job of the later optzn passes easier, allowing the vast amount of
icmp transforms to chew on it.

We transform 840 switches in gcc.c, leading to a 16k byte shrink of the resulting
binary on i386-linux.

The testcase from README.txt now compiles into
  decl  %edi
  cmpl  $3, %edi
  sbbl  %eax, %eax
  andl  $1, %eax
  ret

llvm-svn: 124724
2011-02-02 15:56:22 +00:00
Chris Lattner
1d534245fc add a note, progress unblocked by PR8575 being fixed.
llvm-svn: 124599
2011-01-31 20:23:28 +00:00
Benjamin Kramer
6b3c3de09a Teach DAGCombine to fold fold (sra (trunc (sr x, c1)), c2) -> (trunc (sra x, c1+c2) when c1 equals the amount of bits that are truncated off.
This happens all the time when a smul is promoted to a larger type.

On x86-64 we now compile "int test(int x) { return x/10; }" into
  movslq  %edi, %rax
  imulq $1717986919, %rax, %rax
  movq  %rax, %rcx
  shrq  $63, %rcx
  sarq  $34, %rax <- used to be "shrq $32, %rax; sarl $2, %eax"
  addl  %ecx, %eax

This fires 96 times in gcc.c on x86-64.

llvm-svn: 124559
2011-01-30 16:38:43 +00:00
Chris Lattner
c025bec9e1 this isn't a memset, we do convert dest[i] to one though :)
llvm-svn: 124097
2011-01-24 02:32:00 +00:00
Chris Lattner
1f9ed3b437 with recent work, we now optimize this into:
define i32 @foo(i32 %x) nounwind readnone ssp {
entry:
  %tobool = icmp eq i32 %x, 0
  %tmp5 = select i1 %tobool, i32 2, i32 1
  ret i32 %tmp5
}

llvm-svn: 124091
2011-01-24 01:12:18 +00:00
Anders Carlsson
ba7114ef4c Add a memset loop that LoopIdiomRecognize doesn't recognize.
llvm-svn: 124082
2011-01-23 20:31:00 +00:00
Chris Lattner
08e1bf567f add a note
llvm-svn: 123752
2011-01-18 07:47:48 +00:00
Anders Carlsson
d0103ebf92 Update README.txt to remove the DAE enhancement.
llvm-svn: 123597
2011-01-16 21:26:15 +00:00
Chris Lattner
91f1b21cf1 add some commentary
llvm-svn: 123572
2011-01-16 06:39:44 +00:00
Chandler Carruth
a3261fcca5 Simplify a README.txt entry significantly to expose the core issue.
llvm-svn: 123556
2011-01-16 01:40:23 +00:00
Chris Lattner
d2d217dc46 typo
llvm-svn: 123406
2011-01-13 22:11:56 +00:00
Chris Lattner
6745cd150c memcpy + metadata = bliss :)
llvm-svn: 123405
2011-01-13 22:08:15 +00:00
Chandler Carruth
250dce460c Teach constant folding to perform conversions from constant floating
point values to their integer representation through the SSE intrinsic
calls. This is the last part of a README.txt entry for which I have real
world examples.

llvm-svn: 123206
2011-01-11 01:07:24 +00:00
Owen Anderson
4479341626 Fix a random missed optimization by making InstCombine more aggressive when determining which bits are demanded by
a comparison against a constant.

llvm-svn: 123203
2011-01-11 00:36:45 +00:00
Chris Lattner
c46188944e +0.0 vs -0.0 differences can be handled by looking at the user of the
operation in some cases.

llvm-svn: 123190
2011-01-10 21:01:17 +00:00
Chris Lattner
2bd48ecd43 expand on a note
llvm-svn: 123145
2011-01-10 00:33:01 +00:00
Chris Lattner
7926b7035f typo
llvm-svn: 123142
2011-01-09 23:48:41 +00:00
Chris Lattner
fc6d425076 xref a PR #
llvm-svn: 123141
2011-01-09 23:42:22 +00:00
Chandler Carruth
a4d454ae5e Add a note about the inability to model FP -> int conversions which
perform rounding other than truncation in the IR. Common C code for this
turns into really an LLVM intrinsic call that blocks a lot of further
optimizations.

llvm-svn: 123135
2011-01-09 22:36:18 +00:00
Chandler Carruth
2a30077fed Add a note about a missed FP optimization.
llvm-svn: 123126
2011-01-09 21:00:19 +00:00
Chandler Carruth
17c1672ea9 Another missed memset in std::vector initialization.
llvm-svn: 123116
2011-01-09 11:29:57 +00:00
Chandler Carruth
dcbd7b6eaa Fix a cut-paste-o so that the sample code is correct for my last note.
Also, switch to a more clear 'sink' function with its declaration to
avoid any confusion about 'g'. Thanks for the suggestion Frits.

llvm-svn: 123113
2011-01-09 10:10:59 +00:00
Chandler Carruth
3de0da8801 Another missed optimization of trivial vector code.
llvm-svn: 123112
2011-01-09 09:58:36 +00:00
Chandler Carruth
9220d9fa48 Add a note about vector's size-constructor producing dead stores.
llvm-svn: 123111
2011-01-09 09:58:33 +00:00
Chandler Carruth
815cbfb43c Add a note about a missed memset optimization from std::fill.
llvm-svn: 123103
2011-01-09 01:32:55 +00:00
Benjamin Kramer
62b5a4d14c Revert 122959, it needs more thought. Add it back to README.txt with additional notes.
llvm-svn: 123030
2011-01-07 20:42:20 +00:00
Chris Lattner
2fd8a095b1 With Benjamin's recent amazing patches, we should be able to do even better things :)
llvm-svn: 122978
2011-01-06 22:25:00 +00:00
Benjamin Kramer
4e31a65344 Add a note from llvmdev, this time with more info.
llvm-svn: 122966
2011-01-06 17:35:50 +00:00
Benjamin Kramer
33e41f4986 EarlyCSE does this now (and GVN always did it).
llvm-svn: 122960
2011-01-06 13:19:46 +00:00
Benjamin Kramer
5834b2bab8 InstCombine: If we call llvm.objectsize on a malloc call we can replace it with the size passed to malloc.
llvm-svn: 122959
2011-01-06 13:11:05 +00:00
Chris Lattner
40973baa5f add a note about object size from drystone, add a poorly optimized loop from 179.art.
llvm-svn: 122954
2011-01-06 07:41:22 +00:00
Chris Lattner
69ff12968c add a trivial instcombine missed in Dhrystone
llvm-svn: 122953
2011-01-06 07:09:23 +00:00
Chris Lattner
222b24e2de update a bunch of entries.
llvm-svn: 122700
2011-01-02 18:31:38 +00:00
Chris Lattner
f669d6a901 Allow loop-idiom to run on multiple BB loops, but still only scan the loop
header for now for memset/memcpy opportunities.  It turns out that loop-rotate
is successfully rotating loops, but *DOESN'T MERGE THE BLOCKS*, turning "for 
loops" into 2 basic block loops that loop-idiom was ignoring.

With this fix, we form many *many* more memcpy and memsets than before, including
on the "history" loops in the viterbi benchmark, which look like this:

        for (j=0; j<MAX_history; ++j) {
          history_new[i][j+1] = history[2*i][j];
        }

Transforming these loops into memcpy's speeds up the viterbi benchmark from
11.98s to 3.55s on my machine.  Woo.

llvm-svn: 122685
2011-01-02 07:58:36 +00:00
Chris Lattner
9dadac901f a missed __builtin_object_size case.
llvm-svn: 122676
2011-01-01 22:57:31 +00:00
Chris Lattner
e3e3cb83a5 various updates.
llvm-svn: 122675
2011-01-01 22:52:11 +00:00