Benjamin Kramer
c672ae3ee2
Remove README entry obsoleted by register masks.
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llvm-svn: 154588
2012-04-12 12:47:29 +00:00
Benjamin Kramer
b3055f03e1
Add another note about a missed compare with nsw arithmetic instcombine.
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llvm-svn: 153574
2012-03-28 10:50:18 +00:00
Benjamin Kramer
4be5a4bca4
Add a note about a cute little fabs optimization.
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llvm-svn: 153543
2012-03-27 22:42:42 +00:00
Benjamin Kramer
cc6159f7d9
Add two missed instcombines related to compares with nsw arithmetic.
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llvm-svn: 153542
2012-03-27 22:03:19 +00:00
Benjamin Kramer
f4e9cbfc05
Add two notes for correlated-expression optimizations.
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llvm-svn: 139263
2011-09-07 22:49:26 +00:00
Benjamin Kramer
1cab6179ab
Don't emit a bit test if there is only one case the test can yield false. A simple SETNE is sufficient.
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llvm-svn: 135126
2011-07-14 01:38:42 +00:00
Benjamin Kramer
5079b61657
InstCombine: Fold A-b == C --> b == A-C if A and C are constants.
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The backend already knew this trick.
llvm-svn: 132915
2011-06-13 15:24:24 +00:00
Chris Lattner
f58c2c02b5
clarify this, apparently it is confusing :)
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llvm-svn: 131916
2011-05-23 20:17:44 +00:00
Chris Lattner
3066a7e5ad
add a note.
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llvm-svn: 131863
2011-05-22 18:28:46 +00:00
Chris Lattner
9359dea740
move PR9408 here.
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llvm-svn: 131841
2011-05-22 05:45:06 +00:00
Chris Lattner
01ceb99a05
Transform: "icmp eq (trunc (lshr(X, cst1)), cst" to "icmp (and X, mask), cst"
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when X has multiple uses. This is useful for exposing secondary optimizations,
but the X86 backend isn't ready for this when X has a single use. For example,
this can disable load folding.
This is inching towards resolving PR6627.
llvm-svn: 130238
2011-04-26 20:18:20 +00:00
Chris Lattner
35166f3b22
add a missed bitfield instcombine.
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llvm-svn: 130137
2011-04-25 18:44:26 +00:00
Benjamin Kramer
f6eab5f86e
DAGCombine: fold "(zext x) == C" into "x == (trunc C)" if the trunc is lossless.
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On x86 this allows to fold a load into the cmp, greatly reducing register pressure.
movzbl (%rdi), %eax
cmpl $47, %eax
->
cmpb $47, (%rdi)
This shaves 8k off gcc.o on i386. I'll leave applying the patch in README.txt to Chris :)
llvm-svn: 130005
2011-04-22 18:47:44 +00:00
Chris Lattner
5fa2544086
add a minor missed dag combine that is blocking mid-level optimization
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improvements, that will lead to fixing PR6627.
llvm-svn: 129504
2011-04-14 04:21:42 +00:00
Benjamin Kramer
12ea727553
Add a note.
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llvm-svn: 128286
2011-03-25 17:32:40 +00:00
Eli Friedman
f9d5010081
A bit more analysis of a memset-related README entry.
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llvm-svn: 128107
2011-03-22 20:49:53 +00:00
Eli Friedman
0da0b4aed0
This README entry was fixed recently.
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llvm-svn: 127982
2011-03-21 01:33:03 +00:00
Chris Lattner
871d62dc5b
add a note
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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.
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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.
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llvm-svn: 126103
2011-02-21 02:13:39 +00:00
Chris Lattner
8760c28fe1
add an idiom that loop idiom could theoretically catch.
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llvm-svn: 126101
2011-02-21 01:33:38 +00:00
Duncan Sands
e0ece264ba
This has been implemented.
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llvm-svn: 125738
2011-02-17 08:16:56 +00:00
Chris Lattner
035876162f
add some notes on compares + binops. Remove redundant entries.
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llvm-svn: 125702
2011-02-17 01:43:46 +00:00
Chris Lattner
9f4e529571
Add a few missed xforms from GCC PR14753
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llvm-svn: 125681
2011-02-16 19:16:34 +00:00
Eli Friedman
b409f8da64
Remove outdated README entry.
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llvm-svn: 125660
2011-02-16 07:41:19 +00:00
Eli Friedman
5f848d70fa
Remove outdated README entry.
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llvm-svn: 125659
2011-02-16 07:18:18 +00:00
Eli Friedman
30a64ae1b9
Update README entry.
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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.
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llvm-svn: 124989
2011-02-06 20:16:49 +00:00
Benjamin Kramer
b739613711
SimplifyCFG: Turn switches into sub+icmp+branch if possible.
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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.
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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.
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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 :)
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llvm-svn: 124097
2011-01-24 02:32:00 +00:00
Chris Lattner
1f9ed3b437
with recent work, we now optimize this into:
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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.
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llvm-svn: 124082
2011-01-23 20:31:00 +00:00
Chris Lattner
08e1bf567f
add a note
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llvm-svn: 123752
2011-01-18 07:47:48 +00:00
Anders Carlsson
d0103ebf92
Update README.txt to remove the DAE enhancement.
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llvm-svn: 123597
2011-01-16 21:26:15 +00:00
Chris Lattner
91f1b21cf1
add some commentary
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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.
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llvm-svn: 123556
2011-01-16 01:40:23 +00:00
Chris Lattner
d2d217dc46
typo
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llvm-svn: 123406
2011-01-13 22:11:56 +00:00
Chris Lattner
6745cd150c
memcpy + metadata = bliss :)
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llvm-svn: 123405
2011-01-13 22:08:15 +00:00
Chandler Carruth
250dce460c
Teach constant folding to perform conversions from constant floating
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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
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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
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operation in some cases.
llvm-svn: 123190
2011-01-10 21:01:17 +00:00
Chris Lattner
2bd48ecd43
expand on a note
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llvm-svn: 123145
2011-01-10 00:33:01 +00:00
Chris Lattner
7926b7035f
typo
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llvm-svn: 123142
2011-01-09 23:48:41 +00:00
Chris Lattner
fc6d425076
xref a PR #
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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
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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.
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llvm-svn: 123126
2011-01-09 21:00:19 +00:00
Chandler Carruth
17c1672ea9
Another missed memset in std::vector initialization.
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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.
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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