Make it possible to indicate relaxed floating point requirements at the IR level
through the use of 'fpmath' metadata. Currently this only provides a 'fpaccuracy'
value, which may be a number in ULPs or the keyword 'fast', however the intent is
that this will be extended with additional information about NaN's, infinities
etc later. No optimizations have been hooked up to this so far.
Flip the new block-placement pass to be on by default.
This is mostly to test the waters. I'd like to get results from FNT
build bots and other bots running on non-x86 platforms.
This feature has been pretty heavily tested over the last few months by
me, and it fixes several of the execution time regressions caused by the
inlining work by preventing inlining decisions from radically impacting
block layout.
I've seen very large improvements in yacr2 and ackermann benchmarks,
along with the expected noise across all of the benchmark suite whenever
code layout changes. I've analyzed all of the regressions and fixed
them, or found them to be impossible to fix. See my email to llvmdev for
more details.
I'd like for this to be in 3.1 as it complements the inliner changes,
but if any failures are showing up or anyone has concerns, it is just
a flag flip and so can be easily turned off.
I'm switching it on tonight to try and get at least one run through
various folks' performance suites in case SPEC or something else has
serious issues with it. I'll watch bots and revert if anything shows up.
Remove an overly brittle test. This test will no longer be interesting
once we start changing the block layout, so just nuke it. If anyone has
ideas about how to craft a code layout agnostic form of the test please
let me know.
Add a somewhat hacky heuristic to do something different from whole-loop
rotation. When there is a loop backedge which is an unconditional
branch, we will end up with a branch somewhere no matter what. Try
placing this backedge in a fallthrough position above the loop header as
that will definitely remove at least one branch from the loop iteration,
where whole loop rotation may not.
I haven't seen any benchmarks where this is important but loop-blocks.ll
tests for it, and so this will be covered when I flip the default.
Add convenience methods to MDBuilder for attaching metadata to instructions,
and retrieving it from instructions. I don't have a use for this but is seems
logical for it to exist. While there, remove some 'const' markings from methods
which are in fact 'const' in practice, but aren't logically 'const'.
Richard Barton [Mon, 16 Apr 2012 11:32:10 +0000 (11:32 +0000)]
Add -disassemble support for -show-inst and -show-encode capability llvm-mc. Also refactor so all MC paraphernalia are created once for all uses as much as possible.
The test change is to account for the fact that the default disassembler behaviour has changed with regards to specifying the assembly syntax to use.
Tweak the loop rotation logic to check whether the loop is naturally
laid out in a form with a fallthrough into the header and a fallthrough
out of the bottom. In that case, leave the loop alone because any
rotation will introduce unnecessary branches. If either side looks like
it will require an explicit branch, then the rotation won't add any, do
it to ensure the branch occurs outside of the loop (if possible) and
maximize the benefit of the fallthrough in the bottom.
Change type profile for vpermv back to using operand type for the mask argument to match intrinsic behavior. Add a bitcast to the lowering code to convert mask from v8i32 to v8f32 for vpermps.
Flip the arguments when converting vpermd/vpermps intrinsics into instructions. The intrinsic has the mask as the last operand, but the instruction has it as the second.
Rewrite how machine block placement handles loop rotation.
This is a complex change that resulted from a great deal of
experimentation with several different benchmarks. The one which proved
the most useful is included as a test case, but I don't know that it
captures all of the relevant changes, as I didn't have specific
regression tests for each, they were more the result of reasoning about
what the old algorithm would possibly do wrong. I'm also failing at the
moment to craft more targeted regression tests for these changes, if
anyone has ideas, it would be welcome.
The first big thing broken with the old algorithm is the idea that we
can take a basic block which has a loop-exiting successor and a looping
successor and use the looping successor as the layout top in order to
get that particular block to be the bottom of the loop after layout.
This happens to work in many cases, but not in all.
The second big thing broken was that we didn't try to select the exit
which fell into the nearest enclosing loop (to which we exit at all). As
a consequence, even if the rotation worked perfectly, it would result in
one of two bad layouts. Either the bottom of the loop would get
fallthrough, skipping across a nearer enclosing loop and thereby making
it discontiguous, or it would be forced to take an explicit jump over
the nearest enclosing loop to earch its successor. The point of the
rotation is to get fallthrough, so we need it to fallthrough to the
nearest loop it can.
The fix to the first issue is to actually layout the loop from the loop
header, and then rotate the loop such that the correct exiting edge can
be a fallthrough edge. This is actually much easier than I anticipated
because we can handle all the hard parts of finding a viable rotation
before we do the layout. We just store that, and then rotate after
layout is finished. No inner loops get split across the post-rotation
backedge because we check for them when selecting the rotation.
That fix exposed a latent problem with our exitting block selection --
we should allow the backedge to point into the middle of some inner-loop
chain as there is no real penalty to it, the whole point is that it
*won't* be a fallthrough edge. This may have blocked the rotation at all
in some cases, I have no idea and no test case as I've never seen it in
practice, it was just noticed by inspection.
Finally, all of these fixes, and studying the loops they produce,
highlighted another problem: in rotating loops like this, we sometimes
fail to align the destination of these backwards jumping edges. Fix this
by actually walking the backwards edges rather than relying on loopinfo.
This fixes regressions on heapsort if block placement is enabled as well
as lots of other cases where the previous logic would introduce an
abundance of unnecessary branches into the execution.
Rename "fpaccuracy" metadata to the more generic "fpmath". That's because I'm
thinking of generalizing it to be able to specify other freedoms beyond accuracy
(such as that NaN's don't have to be respected). I'd like the 3.1 release (the
first one with this metadata) to have the more generic name already rather than
having to auto-upgrade it in 3.2.
Hal Finkel [Sat, 14 Apr 2012 07:32:50 +0000 (07:32 +0000)]
Fix an error in BBVectorize important for vectorizing pointer types.
When vectorizing pointer types it is important to realize that potential
pairs cannot be connected via the address pointer argument of a load or store.
This is because even after vectorization, the address is still a scalar because
the address of the higher half of the pair is implicit from the address of the
lower half (it need not be, and should not be, explicitly computed).
Andrew Trick [Fri, 13 Apr 2012 23:29:54 +0000 (23:29 +0000)]
misched: Added CanHandleTerminators.
This is a special flag for targets that really want their block
terminators in the DAG. The default scheduler cannot handle this
correctly, so it becomes the specialized scheduler's responsibility to
schedule terminators.
Benjamin Kramer [Fri, 13 Apr 2012 20:06:17 +0000 (20:06 +0000)]
Reduce malloc traffic in DwarfAccelTable
- Don't copy offsets into HashData, the underlying vector won't change once the table is finalized.
- Allocate HashData and HashDataContents in a BumpPtrAllocator.
- Allocate string map entries in the same allocator.
- Random cleanups.
Kevin Enderby [Fri, 13 Apr 2012 18:46:37 +0000 (18:46 +0000)]
For ARM disassembly only print 32 unsigned bits for the address of branch
targets so if the branch target has the high bit set it does not get printed as:
beq 0xffffffff8008c404
Dan Gohman [Fri, 13 Apr 2012 18:28:58 +0000 (18:28 +0000)]
Consider ObjC runtime calls objc_storeWeak and others which make a copy of
their argument as "escape" points for objc_retainBlock optimization.
This fixes rdar://11229925.
Hal Finkel [Fri, 13 Apr 2012 17:15:33 +0000 (17:15 +0000)]
By default, use Early-CSE instead of GVN for vectorization cleanup.
As has been suggested by Duncan and others, Early-CSE and GVN should
do similar redundancy elimination, but Early-CSE is much less expensive.
Most of my autovectorization benchmarks show a performance regresion, but
all of these are < 0.1%, and so I think that it is still worth using
the less expensive pass.
Catch the Python exception when subprocess.Popen is failing.
For example, if llc cannot be found, the full python stacktrace is displayed
and no interesting information are provided.
+ fail the process when an exception occurs
Silence various build warnings from Hexagon backend that show up in release builds. Mostly converting 'assert(0)' to 'llvm_unreachable' to silence warnings about missing returns. Also fold some variable declarations into asserts to prevent the variables from being unused in release builds.
Fix target specific intrinsic handling to adjust intrinsic number before doing attribute table lookup. Also fix attribute table lookup to handle 'invalid' intrinsic correctly. Fixes PR12542
Remove getElfArchType from ELF.h. It's only used in ELFObjectFile.cpp and there's already a copy there. ELF.h was hiding the one there and causing an unused function warning.
Dan Gohman [Fri, 13 Apr 2012 01:08:28 +0000 (01:08 +0000)]
Use the new Use-aware dominates method to apply the objc runtime
library return value optimization for phi uses. Even when the
phi itself is not dominated, the specific use may be dominated.
Bill Wendling [Fri, 13 Apr 2012 01:06:27 +0000 (01:06 +0000)]
Code-gen may inject code into the IR before it emits the ASM. The linker
obviously cannot know that this code is present, let alone used. So prevent the
internalize pass from internalizing those global values which code-gen may
insert.
Dan Gohman [Fri, 13 Apr 2012 00:59:57 +0000 (00:59 +0000)]
Don't move objc_autorelease calls past autorelease pool boundaries when
optimizing autorelease calls on phi nodes with null operands.
This fixes rdar://11207070.
Dan Gohman [Thu, 12 Apr 2012 23:31:46 +0000 (23:31 +0000)]
Add forms of dominates and isReachableFromEntry that accept a Use
directly instead of a user Instruction. This allows them to test
whether a def dominates a particular operand if the user instruction
is a PHI.
There is an assert at line 558 in ScheduleDAGInstrs::buildSchedGraph(AliasAnalysis *AA).
This assert needs to addressed for post RA scheduler. Until that assert is addressed,
any passes that uses post ra scheduler will fail. So, I am temporarily disabling the
hexagon tests until that fix is in.
The assert is as follows:
assert(!MI->isTerminator() && !MI->isLabel() &&
"Cannot schedule terminators or labels!");
This patch improves the MCJIT runtime dynamic loader by adding new handling
of zero-initialized sections, virtual sections and common symbols
and preventing the loading of sections which are not required for
execution such as debug information.
projects / llvm / log