Commit Graph

2235 Commits

Author SHA1 Message Date
Dmitri Gribenko
5c332dbd30 Add ArrayRef constructor from None, and do the cleanups that this constructor enables
Patch by Robert Wilhelm.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181138 91177308-0d34-0410-b5e6-96231b3b80d8
2013-05-05 00:40:33 +00:00
Filip Pizlo
40be1e8566 This patch breaks up Wrap.h so that it does not have to include all of
the things, and renames it to CBindingWrapping.h.  I also moved 
CBindingWrapping.h into Support/.

This new file just contains the macros for defining different wrap/unwrap 
methods.

The calls to those macros, as well as any custom wrap/unwrap definitions 
(like for array of Values for example), are put into corresponding C++ 
headers.

Doing this required some #include surgery, since some .cpp files relied 
on the fact that including Wrap.h implicitly caused the inclusion of a 
bunch of other things.

This also now means that the C++ headers will include their corresponding 
C API headers; for example Value.h must include llvm-c/Core.h.  I think 
this is harmless, since the C API headers contain just external function 
declarations and some C types, so I don't believe there should be any 
nasty dependency issues here.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180881 91177308-0d34-0410-b5e6-96231b3b80d8
2013-05-01 20:59:00 +00:00
Richard Trieu
8e229c24ed Fix a use after free. RI is freed before the call to getDebugLoc(). To
prevent this, capture the location before RI is freed.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180824 91177308-0d34-0410-b5e6-96231b3b80d8
2013-04-30 22:45:10 +00:00
Adrian Prantl
8960a5c63d Spelling. Thanks, Eric.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180794 91177308-0d34-0410-b5e6-96231b3b80d8
2013-04-30 17:33:32 +00:00
Adrian Prantl
8b11e89b93 Set debug locations for branch instructions created during inlining, even
the inlined function has multiple returns.

rdar://problem/12415623

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180793 91177308-0d34-0410-b5e6-96231b3b80d8
2013-04-30 17:08:16 +00:00
Arnold Schwaighofer
8228ffe72d SimplifyCFG: If convert single conditional stores
This resurrects r179957, but adds code that makes sure we don't touch
atomic/volatile stores:

This transformation will transform a conditional store with a preceeding
uncondtional store to the same location:

 a[i] =
 may-alias with a[i] load
 if (cond)
   a[i] = Y

into an unconditional store.

 a[i] = X
 may-alias with a[i] load
 tmp = cond ? Y : X;
 a[i] = tmp

We assume that on average the cost of a mispredicted branch is going to be
higher than the cost of a second store to the same location, and that the
secondary benefits of creating a bigger basic block for other optimizations to
work on outway the potential case where the branch would be correctly predicted
and the cost of the executing the second store would be noticably reflected in
performance.

hmmer's execution time improves by 30% on an imac12,2 on ref data sets. With
this change we are on par with gcc's performance (gcc also performs this
transformation). There was a 1.2 % performance improvement on a ARM swift chip.
Other tests in the test-suite+external seem to be mostly uninfluenced in my
experiments:
This optimization was triggered on 41 tests such that the executable was
different before/after the patch. Only 1 out of the 40 tests (dealII) was
reproducable below 100% (by about .4%). Given that hmmer benefits so much I
believe this to be a fair trade off.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180731 91177308-0d34-0410-b5e6-96231b3b80d8
2013-04-29 21:28:24 +00:00
Adrian Prantl
9d5d58a49b fix a typo that due to cu&paste quadrupled itself
rdar://problem/13056109

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180618 91177308-0d34-0410-b5e6-96231b3b80d8
2013-04-26 18:10:50 +00:00
Adrian Prantl
163da93023 Bugfix for the debug intrinsic handling in InstCombiner:
Since we can't guarantee that the original dbg.declare instrinsic
is removed by LowerDbgDeclare(), we need to make sure that we are
not inserting the same dbg.value intrinsic over and over.
This removes tons of redundant DIEs when compiling optimized code.

rdar://problem/13056109

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180615 91177308-0d34-0410-b5e6-96231b3b80d8
2013-04-26 17:48:33 +00:00
Adrian Prantl
f48509787a Make sure the instruction right after an inlined function has a
debug location. This solves a problem where range of an inlined
subroutine is emitted wrongly.
Patch by Manman Ren.

Fixes rdar://problem/12415623

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180140 91177308-0d34-0410-b5e6-96231b3b80d8
2013-04-23 19:56:03 +00:00
Eric Christopher
3e39731e88 Move C++ code out of the C headers and into either C++ headers
or the C++ files themselves. This enables people to use
just a C compiler to interoperate with LLVM.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180063 91177308-0d34-0410-b5e6-96231b3b80d8
2013-04-22 22:47:22 +00:00
Arnold Schwaighofer
54d9a3e2df Revert "SimplifyCFG: If convert single conditional stores"
There is the temptation to make this tranform dependent on target information as
it is not going to be beneficial on all (sub)targets. Therefore, we should
probably do this in MI Early-Ifconversion.

This reverts commit r179957. Original commit message:

"SimplifyCFG: If convert single conditional stores

This transformation will transform a conditional store with a preceeding
uncondtional store to the same location:

a[i] =
may-alias with a[i] load
if (cond)
    a[i] = Y
into an unconditional store.

a[i] = X
may-alias with a[i] load
tmp = cond ? Y : X;
a[i] = tmp

We assume that on average the cost of a mispredicted branch is going to be
higher than the cost of a second store to the same location, and that the
secondary benefits of creating a bigger basic block for other optimizations to
work on outway the potential case were the branch would be correctly predicted
and the cost of the executing the second store would be noticably reflected in
performance.

hmmer's execution time improves by 30% on an imac12,2 on ref data sets. With
this change we are on par with gcc's performance (gcc also performs this
transformation). There was a 1.2 % performance improvement on a ARM swift chip.
Other tests in the test-suite+external seem to be mostly uninfluenced in my
experiments:
This optimization was triggered on 41 tests such that the executable was
different before/after the patch. Only 1 out of the 40 tests (dealII) was
reproducable below 100% (by about .4%). Given that hmmer benefits so much I
believe this to be a fair trade off.

I am going to watch performance numbers across the builtbots and will revert
this if anything unexpected comes up."

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179980 91177308-0d34-0410-b5e6-96231b3b80d8
2013-04-21 13:09:04 +00:00
Arnold Schwaighofer
f7af1987dd SimplifyCFG: If convert single conditional stores
This transformation will transform a conditional store with a preceeding
uncondtional store to the same location:

 a[i] =
 may-alias with a[i] load
 if (cond)
   a[i] = Y

into an unconditional store.

 a[i] = X
 may-alias with a[i] load
 tmp = cond ? Y : X;
 a[i] = tmp

We assume that on average the cost of a mispredicted branch is going to be
higher than the cost of a second store to the same location, and that the
secondary benefits of creating a bigger basic block for other optimizations to
work on outway the potential case were the branch would be correctly predicted
and the cost of the executing the second store would be noticably reflected in
performance.

hmmer's execution time improves by 30% on an imac12,2 on ref data sets. With
this change we are on par with gcc's performance (gcc also performs this
transformation). There was a 1.2 % performance improvement on a ARM swift chip.
Other tests in the test-suite+external seem to be mostly uninfluenced in my
experiments:
This optimization was triggered on 41 tests such that the executable was
different before/after the patch. Only 1 out of the 40 tests (dealII) was
reproducable below 100% (by about .4%). Given that hmmer benefits so much I
believe this to be a fair trade off.

I am going to watch performance numbers across the builtbots and will revert
this if anything unexpected comes up.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179957 91177308-0d34-0410-b5e6-96231b3b80d8
2013-04-20 21:42:09 +00:00
Peter Collingbourne
c7ab4f99be Do not optimise fprintf() calls if its return value is used.
Differential Revision: http://llvm-reviews.chandlerc.com/D620

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179661 91177308-0d34-0410-b5e6-96231b3b80d8
2013-04-17 02:01:10 +00:00
Hans Wennborg
a121e24c54 simplifycfg: Fix integer overflow converting switch into icmp.
If a switch instruction has a case for every possible value of its type,
with the same successor, SimplifyCFG would replace it with an icmp ult,
but the computation of the bound overflows in that case, which inverts
the test.

Patch by Jed Davis!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179587 91177308-0d34-0410-b5e6-96231b3b80d8
2013-04-16 08:35:36 +00:00
Joey Gouly
0f57a98a65 Change CloneFunctionInto to always clone Argument attributes induvidually,
rather than checking if the source and destination have the same number of
arguments and copying the attributes over directly.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179169 91177308-0d34-0410-b5e6-96231b3b80d8
2013-04-10 10:37:38 +00:00
Bill Wendling
4c62502470 Add all clauses when merging the landing pads. Duplicates will be handled later on.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177757 91177308-0d34-0410-b5e6-96231b3b80d8
2013-03-22 20:31:05 +00:00
Bill Wendling
63da4062e4 Don't use the removed API.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177749 91177308-0d34-0410-b5e6-96231b3b80d8
2013-03-22 18:49:53 +00:00
Evgeniy Stepanov
7541cd36fd Fix llvm::removeUnreachableBlocks to handle unreachable loops.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177713 91177308-0d34-0410-b5e6-96231b3b80d8
2013-03-22 08:43:04 +00:00
Bill Wendling
d9ff8c83d1 Always forward 'resume' instructions to the outter landing pad.
How did this ever work?

Basically, if you have a function that's inlined into the caller, it may not
have any 'call' instructions, but any 'resume' instructions it may have should
still be forwarded to the outer (caller's) landing pad. This requires that all
of the 'landingpad' instructions in the callee have their clauses merged with
the caller's outer 'landingpad' instruction (hence the bit of ugly code in the
`forwardResume' method).

Testcase in a follow commit to the test-suite repository.

<rdar://problem/13360379> & PR15555


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177680 91177308-0d34-0410-b5e6-96231b3b80d8
2013-03-21 23:30:12 +00:00
Meador Inge
67cb638629 LibCallSimplifier: optimize speed for short-lived instances
Nadav reported a performance regression due to the work I did to
merge the library call simplifier into instcombine [1].  The issue
is that a new LibCallSimplifier object is being created whenever
InstCombiner::runOnFunction is called.  Every time a LibCallSimplifier
object is used to optimize a call it creates a hash table to map from
a function name to an object that optimizes functions of that name.
For short-lived LibCallSimplifier instances this is quite inefficient.
Especially for cases where no calls are actually simplified.

This patch fixes the issue by dropping the hash table and implementing
an explicit lookup function to correlate the function name to the object
that optimizes functions of that name.  This avoids the cost of always
building and destroying the hash table in cases where the LibCallSimplifier
object is short-lived and avoids the cost of building the table when no
simplifications are actually preformed.

On a benchmark containing 100,000 calls where none of them are simplified
I noticed a 30% speedup.  On a benchmark containing 100,000 calls where
all of them are simplified I noticed an 8% speedup.

[1] http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20130304/167639.html

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176840 91177308-0d34-0410-b5e6-96231b3b80d8
2013-03-12 00:08:29 +00:00
Bill Wendling
d5bb20805e Don't remove a landing pad if the invoke requires a table entry.
An invoke may require a table entry. For instance, when the function it calls
is expected to throw.
<rdar://problem/13360379>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176827 91177308-0d34-0410-b5e6-96231b3b80d8
2013-03-11 20:53:00 +00:00
Pekka Jaaskelainen
784ae47413 Fixed a crash when cloning a function into a function with
different size argument list and without attributes in the
arguments.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176632 91177308-0d34-0410-b5e6-96231b3b80d8
2013-03-07 16:46:43 +00:00
Andrew Trick
119003f2a2 SimplifyCFG fix for volatile load/store.
Fixes rdar:13349374.

Volatile loads and stores need to be preserved even if the language
standard says they are undefined. "volatile" in this context means "get
out of the way compiler, let my platform handle it".

Additionally, this is the only way I know of with llvm to write to the
first page (when hardware allows) without dropping to assembly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176599 91177308-0d34-0410-b5e6-96231b3b80d8
2013-03-07 01:03:35 +00:00
Preston Gurd
9a2cfffdb6 Bypass Slow Divides
* Only apply divide bypass optimization when not optimizing for size. 
* Fixed bug caused by constant for 0 value of type Int32,
  used dividend type to generate the constant instead.
* For atom x86-64 apply the divide bypass to use 16-bit divides instead of
  64-bit divides when operand values are small enough.
* Added lit tests for 64-bit divide bypass.

Patch by Tyler Nowicki!




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176442 91177308-0d34-0410-b5e6-96231b3b80d8
2013-03-04 18:13:57 +00:00
Peter Collingbourne
328d1b6500 Modify {Call,Invoke}Inst::addAttribute to take an AttrKind.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176397 91177308-0d34-0410-b5e6-96231b3b80d8
2013-03-02 01:20:18 +00:00
Nadav Rotem
f26b4f05b3 For each function that we optimize we initialize a new list of lib functions. For each function name we malloc memory. This patch changes the Libcall map to use BumpPtrAllocator. Now we malloc only once. This speeds up instcombine by a few % on a large c++ program.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176170 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-27 05:53:43 +00:00
Pedro Artigas
b3201c5cf1 Enhance integer division emulation support to handle types smaller than 32 bits,
enhancement done the trivial way; by extending inputs and truncating outputs 
which is addequate for targets with little or no support for integer arithmetic
on integer types less than 32 bits.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176139 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-26 23:33:20 +00:00
Bill Wendling
143d46476c Implement the NoBuiltin attribute.
The 'nobuiltin' attribute is applied to call sites to indicate that LLVM should
not treat the callee function as a built-in function. I.e., it shouldn't try to
replace that function with different code.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175835 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-22 00:12:35 +00:00
Bill Wendling
df8a668e3f Temporarily revert r175470 for more review.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175476 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-19 00:52:45 +00:00
Bill Wendling
2af5035a1d Check to see if the 'no-builtin' attribute is set before simplifying a library call.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175470 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-18 23:17:16 +00:00
Jakub Staszak
4fa57932c7 Remove #includes from the commonly used LoopInfo.h.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174786 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-09 01:04:28 +00:00
Chad Rosier
33daeab1bb [SimplifyLibCalls] Library call simplification doen't work if the call site
isn't using the default calling convention.  However, if the transformation is
from a call to inline IR, then the calling convention doesn't matter.
rdar://13157990

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174724 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-08 18:00:14 +00:00
Chad Rosier
1e45487dfd [SjLj Prepare] When demoting an invoke instructions to the stack, if the normal
edge is critical, then split it so we can insert the store.
rdar://13126179

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174418 91177308-0d34-0410-b5e6-96231b3b80d8
2013-02-05 18:23:10 +00:00
Manman Ren
16d1a6bf08 Linker: correctly link in dbg.declare
This is a re-worked version of r174048.
Given source IR:
call void @llvm.dbg.declare(metadata !{i32* %argc.addr}, metadata !14), !dbg !15
we used to generate 
call void @llvm.dbg.declare(metadata !27, metadata !28), !dbg !29
!27 = metadata !{null}

With this patch, we will correctly generate
call void @llvm.dbg.declare(metadata !{i32* %argc.addr}, metadata !27), !dbg !28

Looking up %argc.addr in ValueMap will return null, since %argc.addr is already
correctly set up, we can use identity mapping.

rdar://problem/13089880


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174093 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-31 21:19:18 +00:00
Alexey Samsonov
e22df330a3 Revert r173946. This breaks compilation of googletest with Clang
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174048 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-31 08:02:11 +00:00
Bill Wendling
ac72eb264c Remove addRetAttributes and addFnAttributes, which aren't useful abstractions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173992 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-30 23:40:31 +00:00
Manman Ren
1229c0cb10 Linker: correctly link in dbg.declare
Given source IR:
call void @llvm.dbg.declare(metadata !{i32* %argc.addr}, metadata !14), !dbg !15
we used to generate 
call void @llvm.dbg.declare(metadata !27, metadata !28), !dbg !29
!27 = metadata !{null}

With this patch, we will correctly generate
call void @llvm.dbg.declare(metadata !{i32* %argc.addr}, metadata !27), !dbg !28

Looking up %argc.addr in ValueMap will return null, since %argc.addr is already
correctly set up, we can use identity mapping.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173946 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-30 17:42:15 +00:00
Chandler Carruth
455151e4f7 Re-revert r173342, without losing the compile time improvements, flat
out bug fixes, or functionality preserving refactorings.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173610 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-27 06:42:03 +00:00
Bill Wendling
32a5795822 Convert BuildLibCalls.cpp to using the AttributeSet methods instead of AttributeWithIndex.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173536 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-26 00:03:11 +00:00
Chandler Carruth
baf868b9b8 Switch this code away from Value::isUsedInBasicBlock. That code either
loops over instructions in the basic block or the use-def list of the
value, neither of which are really efficient when repeatedly querying
about values in the same basic block.

What's more, we already know that the CondBB is small, and so we can do
a much more efficient test by counting the uses in CondBB, and seeing if
those account for all of the uses.

Finally, we shouldn't blanket fail on any such instruction, instead we
should conservatively assume that those instructions are part of the
cost.

Note that this actually fixes a bug in the pass because
isUsedInBasicBlock has a really terrible bug in it. I'll fix that in my
next commit, but the fix for it would make this code suddenly take the
compile time hit I thought it already was taking, so I wanted to go
ahead and migrate this code to a faster & better pattern.

The bug in isUsedInBasicBlock was also causing other tests to test the
wrong thing entirely: for example we weren't actually disabling
speculation for floating point operations as intended (and tested), but
the test passed because we failed to speculate them due to the
isUsedInBasicBlock failure.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173417 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-25 05:40:09 +00:00
Benjamin Kramer
d5a80c7358 Reapply chandlerc's r173342 now that the miscompile it was triggering is fixed.
Original commit message:
Plug TTI into the speculation logic, giving it a real cost interface
that can be specialized by targets.

The goal here is not to be more aggressive, but to just be more accurate
with very obvious cases. There are instructions which are known to be
truly free and which were not being modeled as such in this code -- see
the regression test which is distilled from an inner loop of zlib.

Everywhere the TTI cost model is insufficiently conservative I've added
explicit checks with FIXME comments to go add proper modelling of these
cost factors.

If this causes regressions, the likely solution is to make TTI even more
conservative in its cost estimates, but test cases will help here.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173357 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 16:44:25 +00:00
Chandler Carruth
eacef325c6 Revert r173342 temporarily. It appears to cause a very late miscompile
of stage2 in a bootstrap. Still investigating....

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173343 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 13:24:24 +00:00
Chandler Carruth
1f255419d4 Plug TTI into the speculation logic, giving it a real cost interface
that can be specialized by targets.

The goal here is not to be more aggressive, but to just be more accurate
with very obvious cases. There are instructions which are known to be
truly free and which were not being modeled as such in this code -- see
the regression test which is distilled from an inner loop of zlib.

Everywhere the TTI cost model is insufficiently conservative I've added
explicit checks with FIXME comments to go add proper modelling of these
cost factors.

If this causes regressions, the likely solution is to make TTI even more
conservative in its cost estimates, but test cases will help here.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173342 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 12:39:29 +00:00
Chandler Carruth
47d8f6dca5 Address a large chunk of this FIXME by accumulating the cost for
unfolded constant expressions rather than checking each one
independently.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173341 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 12:05:17 +00:00
Chandler Carruth
681add7a63 Switch the constant expression speculation cost evaluation away from
a cost fuction that seems both a bit ad-hoc and also poorly suited to
evaluating constant expressions.

Notably, it is missing any support for trivial expressions such as
'inttoptr'. I could fix this routine, but it isn't clear to me all of
the constraints its other users are operating under.

The core protection that seems relevant here is avoiding the formation
of a select instruction wich a further chain of select operations in
a constant expression operand. Just explicitly encode that constraint.

Also, update the comments and organization here to make it clear where
this needs to go -- this should be driven off of real cost measurements
which take into account the number of constants expressions and the
depth of the constant expression tree.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173340 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 11:53:01 +00:00
Chandler Carruth
2c107a8020 Rephrase the speculating scan of the conditional BB to be phrased in
terms of cost rather than hoisting a single instruction.

This does *not* change the cost model! We still set the cost threshold
at 1 here, it's just that we track it by accumulating cost rather than
by storing an instruction.

The primary advantage is that we no longer leave no-op intrinsics in the
basic block. For example, this will now move both debug info intrinsics
and a single instruction, instead of only moving the instruction and
leaving a basic block with nothing bug debug info intrinsics in it, and
those intrinsics now no longer ordered correctly with the hoisted value.

Instead, we now splice the entire conditional basic block's instruction
sequence.

This also places the code for checking the safety of hoisting next to
the code computing the cost.

Currently, the only observable side-effect of this change is that debug
info intrinsics are no longer abandoned. I'm not sure how to craft
a test case for this, and my real goal was the refactoring, but I'll
talk to Dave or Eric about how to add a test case for this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173339 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 11:52:58 +00:00
Chandler Carruth
0afa33115c Simplify the PHI node operand rewriting.
Previously, the code would scan the PHI nodes and build up a small
setvector of candidate value pairs in phi nodes to go and rewrite. Once
certain the rewrite could be performed, the code walks the set, and for
each one re-scans the entire PHI node list looking for nodes to rewrite
operands.

Instead, scan the PHI nodes once to check for hazards, and then scan it
a second time to rewrite the operands to selects. No set vector, and
a max of two scans.

The only downside is that we might form identical selects, but
instcombine or anything else should fold those easily, and it seems
unlikely to happen often.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173337 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 10:40:51 +00:00
Chandler Carruth
6cf7a91d12 Give the basic block variables here names based on the if-then-end
structure being analyzed. No functionality changed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173334 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 09:59:39 +00:00
Chandler Carruth
9e62095261 Lift a cheap early exit test above loops and other complex early exit
tests. No need to pay the high cost when we're never going to do
anything.

No functionality changed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173331 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 08:22:40 +00:00
Chandler Carruth
c61bc7a90c Spiff up the comment on this method, making the example a bit more
pretty in doxygen, adding some of the details actually present in
a classic example where this matters (a loop from gzip and many other
compression algorithms), and a cautionary note about the risks inherent
in the transform. This has come up on the mailing lists recently, and
I suspect folks reading this code could benefit from going and looking
at the MI pass that can really deal with these issues.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173329 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 08:05:06 +00:00