Commit Graph

445 Commits

Author SHA1 Message Date
Chandler Carruth 321c6a7c50 Revert r173342 temporarily. It appears to cause a very late miscompile
of stage2 in a bootstrap. Still investigating....

llvm-svn: 173343
2013-01-24 13:24:24 +00:00
Chandler Carruth 5f4519309f 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.

llvm-svn: 173342
2013-01-24 12:39:29 +00:00
Chandler Carruth 01bffaad03 Address a large chunk of this FIXME by accumulating the cost for
unfolded constant expressions rather than checking each one
independently.

llvm-svn: 173341
2013-01-24 12:05:17 +00:00
Chandler Carruth 8a21005cca 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.

llvm-svn: 173340
2013-01-24 11:53:01 +00:00
Chandler Carruth 7481ca8ff5 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.

llvm-svn: 173339
2013-01-24 11:52:58 +00:00
Chandler Carruth 76aacbd874 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.

llvm-svn: 173337
2013-01-24 10:40:51 +00:00
Chandler Carruth e2a779f3a7 Give the basic block variables here names based on the if-then-end
structure being analyzed. No functionality changed.

llvm-svn: 173334
2013-01-24 09:59:39 +00:00
Chandler Carruth 1d20c02f55 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.

llvm-svn: 173331
2013-01-24 08:22:40 +00:00
Chandler Carruth 8a4a16618f 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.

llvm-svn: 173329
2013-01-24 08:05:06 +00:00
Duncan Sands 5924545c0c Initialize the components of this class. Otherwise GCC thinks that Array may be
used uninitialized, since it fails to understand that Array is only used when
SingleValue is not, and outputs a warning.  It also seems generally safer given
that the constructor is non-trivial and has plenty of early exits.

llvm-svn: 173242
2013-01-23 09:09:50 +00:00
Chandler Carruth 0b4ef9cedc Make SimplifyCFG simply depend upon TargetTransformInfo and pass it
through as a reference rather than a pointer. There is always *some*
implementation of this available, so this simplifies code by not having
to test for whether it is available or not.

Further, it turns out there were piles of places where SimplifyCFG was
recursing and not passing down either TD or TTI. These are fixed to be
more pedantically consistent even though I don't have any particular
cases where it would matter.

llvm-svn: 171691
2013-01-07 03:53:25 +00:00
Chandler Carruth d3e73556d6 Move TargetTransformInfo to live under the Analysis library. This no
longer would violate any dependency layering and it is in fact an
analysis. =]

llvm-svn: 171686
2013-01-07 03:08:10 +00:00
Chandler Carruth 6db43e6ca3 Switch SimplifyCFG over to the TargetTransformInfo interface rather than
the ScalarTargetTransformInfo interface.

llvm-svn: 171617
2013-01-05 10:05:26 +00:00
Chandler Carruth 9fb823bbd4 Move all of the header files which are involved in modelling the LLVM IR
into their new header subdirectory: include/llvm/IR. This matches the
directory structure of lib, and begins to correct a long standing point
of file layout clutter in LLVM.

There are still more header files to move here, but I wanted to handle
them in separate commits to make tracking what files make sense at each
layer easier.

The only really questionable files here are the target intrinsic
tablegen files. But that's a battle I'd rather not fight today.

I've updated both CMake and Makefile build systems (I think, and my
tests think, but I may have missed something).

I've also re-sorted the includes throughout the project. I'll be
committing updates to Clang, DragonEgg, and Polly momentarily.

llvm-svn: 171366
2013-01-02 11:36:10 +00:00
Chandler Carruth ed0881b2a6 Use the new script to sort the includes of every file under lib.
Sooooo many of these had incorrect or strange main module includes.
I have manually inspected all of these, and fixed the main module
include to be the nearest plausible thing I could find. If you own or
care about any of these source files, I encourage you to take some time
and check that these edits were sensible. I can't have broken anything
(I strictly added headers, and reordered them, never removed), but they
may not be the headers you'd really like to identify as containing the
API being implemented.

Many forward declarations and missing includes were added to a header
files to allow them to parse cleanly when included first. The main
module rule does in fact have its merits. =]

llvm-svn: 169131
2012-12-03 16:50:05 +00:00
Chandler Carruth d9ef81e133 Fix non-determinism introduced in r168970 and pointed out by Duncan.
We're iterating over a non-deterministically ordered container looking
for two saturating flags. To do this correctly, we have to saturate
both, and only stop looping if both saturate to their final value.
Otherwise, which flag we see first changes the result.

This is also a micro-optimization of the previous version as now we
don't go into the (possibly expensive) test logic once the first
violation of either constraint is detected.

llvm-svn: 168989
2012-11-30 09:34:29 +00:00
Chandler Carruth 77d433dafe Rearrange the comments, control flow, and variable names; no
functionality changed.

Evan's commit r168970 moved the code that the primary comment in this
function referred to to the other end of the function without moving the
comment, and there has been a steady creep of "boolean" logic in it that
is simpler if handled via early exit. That way each special case can
have its own comments. I've also made the variable name a bit more
explanatory than "AllFit". This is in preparation to fix the
non-deterministic output of this function.

llvm-svn: 168988
2012-11-30 09:26:25 +00:00
Evan Cheng 65df808f62 Fix logic to determine whether to turn a switch into a lookup table. When
the tables cannot fit in registers (i.e. bitmap), do not emit the table
if it's using an illegal type.

rdar://12779436

llvm-svn: 168970
2012-11-30 02:02:42 +00:00
Hans Wennborg 7b8af0ea05 SimplifyCFG: Don't assume non-null ScalarTargetTransformInfo.
Patch by Pekka Jääskeläinen!

llvm-svn: 168176
2012-11-16 18:22:08 +00:00
Andrew Trick 7656f6dbf7 misspell
llvm-svn: 168058
2012-11-15 18:40:31 +00:00
Andrew Trick 90f5029118 whitespace
llvm-svn: 168057
2012-11-15 18:40:29 +00:00
Hans Wennborg c3c8d95c51 Only do switch-to-lookup table transformation when TargetTransformInfo
is available.

llvm-svn: 167552
2012-11-07 21:35:12 +00:00
Chandler Carruth 7ec5085e01 Revert the series of commits starting with r166578 which introduced the
getIntPtrType support for multiple address spaces via a pointer type,
and also introduced a crasher bug in the constant folder reported in
PR14233.

These commits also contained several problems that should really be
addressed before they are re-committed. I have avoided reverting various
cleanups to the DataLayout APIs that are reasonable to have moving
forward in order to reduce the amount of churn, and minimize the number
of commits that were reverted. I've also manually updated merge
conflicts and manually arranged for the getIntPtrType function to stay
in DataLayout and to be defined in a plausible way after this revert.

Thanks to Duncan for working through this exact strategy with me, and
Nick Lewycky for tracking down the really annoying crasher this
triggered. (Test case to follow in its own commit.)

After discussing with Duncan extensively, and based on a note from
Micah, I'm going to continue to back out some more of the more
problematic patches in this series in order to ensure we go into the
LLVM 3.2 branch with a reasonable story here. I'll send a note to
llvmdev explaining what's going on and why.

Summary of reverted revisions:

r166634: Fix a compiler warning with an unused variable.
r166607: Add some cleanup to the DataLayout changes requested by
         Chandler.
r166596: Revert "Back out r166591, not sure why this made it through
         since I cancelled the command. Bleh, sorry about this!
r166591: Delete a directory that wasn't supposed to be checked in yet.
r166578: Add in support for getIntPtrType to get the pointer type based
         on the address space.
llvm-svn: 167221
2012-11-01 08:07:29 +00:00
Hans Wennborg b71f72aa82 Remove fixme about unreachable cases from SwitchToLookupTable
SimplifyCFG will have removed those cases for us.

llvm-svn: 167132
2012-10-31 16:15:25 +00:00
Hans Wennborg 4fef2fec3d Address Duncan's comments on r167121.
llvm-svn: 167130
2012-10-31 15:31:09 +00:00
Hans Wennborg 09acdb9a16 Address Duncan's comments on r167115
- Use 0 instead of NULL
 - Helper function for "dyn_cast, else lookup in the constant pool".

llvm-svn: 167121
2012-10-31 15:14:39 +00:00
Hans Wennborg 793b342dcf Fix false -> NULL conversion from r167115 spotted by Benjamin Kramer.
llvm-svn: 167117
2012-10-31 14:36:48 +00:00
Hans Wennborg 9e74dd97b8 Do simple constant propagation in lookup table formation for switches
By propagating the value for the switch condition, LLVM can now build
lookup tables for code such as:

  switch (x) {
    case 1: return 5;
    case 2: return 42;
    case 3: case 4: case 5:
      return x - 123;
    default:
      return 123;
  }

Given that x is known for each case, "x - 123" becomes a constant for
cases 3, 4, and 5.

llvm-svn: 167115
2012-10-31 13:42:45 +00:00
Hans Wennborg f3254838e4 Use TargetTransformInfo to control switch-to-lookup table transformation
When the switch-to-lookup tables transform landed in SimplifyCFG, it
was pointed out that this could be inappropriate for some targets.
Since there was no way at the time for the pass to know anything about
the target, an awkward reverse-transform was added in CodeGenPrepare
that turned lookup tables back into switches for some targets.

This patch uses the new TargetTransformInfo to determine if a
switch should be transformed, and removes
CodeGenPrepare::ConvertLoadToSwitch.

llvm-svn: 167011
2012-10-30 11:23:25 +00:00
Duncan Sands 5bdd9dda48 Remove a wrapper around getIntPtrType added to GVN by Hal in commit 166624 (the
wrapper returns a vector of integers when passed a vector of pointers) by having
getIntPtrType itself return a vector of integers in this case.  Outside of this
wrapper, I didn't find anywhere in the codebase that was relying on the old
behaviour for vectors of pointers, so give this a whirl through the buildbots.

llvm-svn: 166939
2012-10-29 17:31:46 +00:00
Jakob Stoklund Olesen 977f41a1fa Also optimize large switch statements.
The isValueEqualityComparison() guard at the top of SimplifySwitch()
only applies to some of the possible transformations.

The newer transformations work just fine on large switches, and the
check on predecessor count is nonsensical.

llvm-svn: 166710
2012-10-25 18:51:15 +00:00
Micah Villmow 12d9127833 Add in support for getIntPtrType to get the pointer type based on the address space.
This checkin also adds in some tests that utilize these paths and updates some of the
clients.

llvm-svn: 166578
2012-10-24 15:52:52 +00:00
Benjamin Kramer c5b0678cf8 Simplify code. No functionality change.
llvm-svn: 165904
2012-10-14 11:15:42 +00:00
Manman Ren 97c1876256 PGO: create metadata for switch only if it has more than one targets.
When all cases of a switch statement are dead, the weights vector only has one
element, and we will get an ssertion failure when calling createBranchWeights.

llvm-svn: 165759
2012-10-11 22:28:34 +00:00
Micah Villmow cdfe20b97f Move TargetData to DataLayout.
llvm-svn: 165402
2012-10-08 16:38:25 +00:00
Benjamin Kramer d12e82e523 SimplifyCFG: Enhance the "remove CFG edge that leads to null pointer dereference" optimization to also handle instructions with multiple uses.
We conservatively only check the first use to avoid walking long use chains.
This catches the common case of having both a load and a store to a pointer
supplied by a PHI node.

llvm-svn: 165232
2012-10-04 16:11:49 +00:00
Benjamin Kramer 9fc3dc7781 SimplifyCFG: Don't crash when forming a switch bitmap with an undef default value.
Fixes PR13985.

llvm-svn: 164934
2012-10-01 11:31:48 +00:00
Benjamin Kramer f064b65a94 SimplifyCFG: Enumerating all predecessors of a BB can be expensive (switches), avoid it if possible.
No functionality change.

llvm-svn: 164923
2012-09-30 21:03:56 +00:00
Benjamin Kramer c2081d1c19 Fix a integer overflow in SimplifyCFG's look up table formation logic.
If the width is very large it gets truncated from uint64_t to uint32_t when
passed to TD->fitsInLegalInteger. The truncated value can fit in a register.
This manifested in massive memory usage or crashes (PR13946).

llvm-svn: 164784
2012-09-27 18:29:58 +00:00
Hans Wennborg cd3a11f725 Address Duncan's comments on r164684:
- Put statistics in alphabetical order
- Don't use getZextValue when building TableInt, just use APInts
- Introduce Create{Z,S}ExtOrTrunc in IRBuilder.

llvm-svn: 164696
2012-09-26 14:01:53 +00:00
Hans Wennborg f2e2c108dd Address Duncan's comments on r164682:
- Finish assert messages with exclamation mark
- Move overflow checking into ShouldBuildLookupTable.

llvm-svn: 164692
2012-09-26 11:07:37 +00:00
Hans Wennborg 39583b88a0 SimplifyCFG: Make the switch-to-lookup table transformation store the
tables in bitmaps when they fit in a target-legal register.

This saves some space, and it also allows for building tables that would
otherwise be deemed too sparse.

One interesting case that this hits is example 7 from
http://blog.regehr.org/archives/320. We currently generate good code
for this when lowering the switch to the selection DAG: we build a
bitmask to decide whether to jump to one block or the other. My patch
will result in the same bitmask, but it removes the need for the jump,
as the return value can just be retrieved from the mask.

llvm-svn: 164684
2012-09-26 09:44:49 +00:00
Hans Wennborg 776d7126b7 SimplifyCFG: Refactor the switch-to-lookup table transformation by
breaking out the building of lookup tables into a separate class.

llvm-svn: 164682
2012-09-26 09:34:53 +00:00
Manman Ren 93ab64916f SimplifyCFG: sink common codes from IF, ELSE blocks down to END block.
We already have HoistThenElseCodeToIf, this patch implements
SinkThenElseCodeToEnd. When END block has only two predecessors and each
predecessor terminates with unconditional branches, we compare instructions in
IF and ELSE blocks backwards and check whether we can sink the common
instructions down.

rdar://12191395

llvm-svn: 164325
2012-09-20 22:37:36 +00:00
Hans Wennborg f744fa917d SimplifyCFG: Don't generate invalid code for switch used to initialize
two variables where the first variable is returned and the second
ignored.

I don't think this occurs in practice (other passes should have cleaned
up the unused phi node), but it should still be handled correctly.

Also make the logic for determining if we should return early less
sketchy.

llvm-svn: 164225
2012-09-19 14:24:21 +00:00
Manman Ren 5657555357 PGO: preserve branch-weight metadata when simplifying Switch to a sub, an icmp
and a conditional branch; also when removing dead cases from a switch.

llvm-svn: 164084
2012-09-18 00:47:33 +00:00
Manman Ren ce48ea7e25 PGO: preserve branch-weight metadata when simplifying Switch
Hanlde the case when we split the default edge if the default target has "icmp"
and unconditinal branch.

llvm-svn: 164076
2012-09-17 23:07:43 +00:00
Manman Ren 774246a3a9 PGO: preserve branch-weight metadata when simplifying SwitchOnSelect.
llvm-svn: 164068
2012-09-17 22:28:55 +00:00
Manman Ren 2d4c10fc49 PGO: preserve branch-weight metadata when simplifying two branches with a common
destination in SimplifyCondBranchToCondBranch.

llvm-svn: 164054
2012-09-17 21:30:40 +00:00
Axel Naumann 4a1270691e Fix a few vars that can end up being used without initialization.
The cases where no initialization happens should still be checked for logic flaws.

llvm-svn: 164032
2012-09-17 14:20:57 +00:00