Optimizations like LoadPRE in GVN will insert new instructions.
If the insertion point is in a already processed BB, they should
get a value number explicitly. If the insertion point is after
current instruction, then just leave it. However, current GVN framework
has no support for it.
In this patch, we just bail out if a VN can't be found.
Dfferential Revision: http://reviews.llvm.org/D14670
A test/Transforms/GVN/pr25440.ll
M lib/Transforms/Scalar/GVN.cpp
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253536 91177308-0d34-0410-b5e6-96231b3b80d8
This bug would manifest in some very specific cases where all the following
conditions are fullfilled:
- GVN didn't remove block
- The regular GVN iteration didn't change the IR
- PRE is enabled
- PRE will not split critical edge
- The last instruction processed by PRE didn't change the IR
Because the CallGraph PassManager relies on this returned value to decide
if it needs to recompute a node after the execution of Function passes,
not returning the right value can lead to unexpected results.
Fix for: https://llvm.org/bugs/show_bug.cgi?id=24715
Patch by Wenxiang Qiu <vincentqiuuu@gmail.com>
From: Mehdi Amini <mehdi.amini@apple.com>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253518 91177308-0d34-0410-b5e6-96231b3b80d8
Note, this was reviewed (and more details are in) http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20151109/312083.html
These intrinsics currently have an explicit alignment argument which is
required to be a constant integer. It represents the alignment of the
source and dest, and so must be the minimum of those.
This change allows source and dest to each have their own alignments
by using the alignment attribute on their arguments. The alignment
argument itself is removed.
There are a few places in the code for which the code needs to be
checked by an expert as to whether using only src/dest alignment is
safe. For those places, they currently take the minimum of src/dest
alignments which matches the current behaviour.
For example, code which used to read:
call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dest, i8* %src, i32 500, i32 8, i1 false)
will now read:
call void @llvm.memcpy.p0i8.p0i8.i32(i8* align 8 %dest, i8* align 8 %src, i32 500, i1 false)
For out of tree owners, I was able to strip alignment from calls using sed by replacing:
(call.*llvm\.memset.*)i32\ [0-9]*\,\ i1 false\)
with:
$1i1 false)
and similarly for memmove and memcpy.
I then added back in alignment to test cases which needed it.
A similar commit will be made to clang which actually has many differences in alignment as now
IRBuilder can generate different source/dest alignments on calls.
In IRBuilder itself, a new argument was added. Instead of calling:
CreateMemCpy(Dst, Src, getInt64(Size), DstAlign, /* isVolatile */ false)
you now call
CreateMemCpy(Dst, Src, getInt64(Size), DstAlign, SrcAlign, /* isVolatile */ false)
There is a temporary class (IntegerAlignment) which takes the source alignment and rejects
implicit conversion from bool. This is to prevent isVolatile here from passing its default
parameter to the source alignment.
Note, changes in future can now be made to codegen. I didn't change anything here, but this
change should enable better memcpy code sequences.
Reviewed by Hal Finkel.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253511 91177308-0d34-0410-b5e6-96231b3b80d8
We sometimes create intermediate subtract instructions during
reassociation. Adding these to the worklist to revisit exposes many
additional reassociation opportunities.
Patch by Aditya Nandakumar.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253240 91177308-0d34-0410-b5e6-96231b3b80d8
We tried to move the insertion point beyond instructions like landingpad
and cleanuppad.
However, we *also* tried to move past catchpad. This is problematic
because catchpad is also a terminator.
This fixes PR25541.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253238 91177308-0d34-0410-b5e6-96231b3b80d8
Summary: Moving landingpads into successor basic blocks makes the
verifier sad. Teach Sink that much like PHI nodes and terminator
instructions, landingpads (and cleanuppads, etc.) may not be moved
between basic blocks.
Reviewers: majnemer
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D14475
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253182 91177308-0d34-0410-b5e6-96231b3b80d8
This allows us to transform the below loop into a memcpy.
void test(unsigned *__restrict__ a, unsigned *__restrict__ b) {
for (int i = 2047; i >= 0; --i) {
a[i] = b[i];
}
}
This is the memcpy version of r251518, which added support for memset with
negative strided loops.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253091 91177308-0d34-0410-b5e6-96231b3b80d8
This change prevents uninteresting stores from being inserted into the list of
candidate stores for memset/memcpy conversion.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252926 91177308-0d34-0410-b5e6-96231b3b80d8
First create a list of candidates, then transform. This simplifies the code in
that you have don't have to worry that you may be using an invalidated
iterator.
Previously, each time we created a memset/memcpy we would reevaluate the entire
loop potentially resulting in lots of redundant work for large basic blocks.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252817 91177308-0d34-0410-b5e6-96231b3b80d8
This is fix for PR24059.
When we are hoisting instruction above some condition it may turn out
that metadata on this instruction was control dependant on the condition.
This metadata becomes invalid and we need to drop it.
This patch should cover most obvious places of speculative execution (which
I have found by greping isSafeToSpeculativelyExecute). I think there are more
cases but at least this change covers the severe ones.
Differential Revision: http://reviews.llvm.org/D14398
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252604 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
LAA currently generates a set of SCEV predicates that must be checked by users.
In the case of Loop Distribute/Loop Load Elimination, no such predicates could have
been emitted, since we don't allow stride versioning. However, in the future there
could be SCEV predicates that will need to be checked.
This change adds support for SCEV predicate versioning in the Loop Distribute, Loop
Load Eliminate and the loop versioning infrastructure.
Reviewers: anemet
Subscribers: mssimpso, sanjoy, llvm-commits
Differential Revision: http://reviews.llvm.org/D14240
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252467 91177308-0d34-0410-b5e6-96231b3b80d8
Some implicit ilist iterator conversions have crept back into Analysis,
Transforms, Hexagon, and llvm-stress. This removes them.
I'll commit a patch immediately after this to disallow them (in a
separate patch so that it's easy to revert if necessary).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252371 91177308-0d34-0410-b5e6-96231b3b80d8
This marker prevents optimization passes from adding 'tail' or
'musttail' markers to a call. Is is used to prevent tail call
optimization from being performed on the call.
rdar://problem/22667622
Differential Revision: http://reviews.llvm.org/D12923
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252368 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
This change makes the `isImpliedCondition` interface similar to the rest
of the functions in ValueTracking (in that it takes a DataLayout,
AssumptionCache etc.). This is an NFC, intended to make a later diff
less noisy.
Depends on D14369
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D14391
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252333 91177308-0d34-0410-b5e6-96231b3b80d8
In my previous change to CVP (251606), I made CVP much more aggressive about trying to constant fold comparisons. This patch is a reversal in direction. Rather than being agressive about every compare, we restore the non-block local restriction for most, and then try hard for compares feeding returns.
The motivation for this is two fold:
* The more I thought about it, the less comfortable I got with the possible compile time impact of the other approach. There have been no reported issues, but after talking to a couple of folks, I've come to the conclusion the time probably isn't justified.
* It turns out we need to know the context to leverage the full power of LVI. In particular, asking about something at the end of it's block (the use of a compare in a return) will frequently get more precise results than something in the middle of a block. This is an implementation detail, but it's also hard to get around since mid-block queries have to reason about possible throwing instructions and don't get to use most of LVI's block focused infrastructure. This will become particular important when combined with http://reviews.llvm.org/D14263.
Differential Revision: http://reviews.llvm.org/D14271
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252032 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
The goal of this pass is to perform store-to-load forwarding across the
backedge of a loop. E.g.:
for (i)
A[i + 1] = A[i] + B[i]
=>
T = A[0]
for (i)
T = T + B[i]
A[i + 1] = T
The pass relies on loop dependence analysis via LoopAccessAnalisys to
find opportunities of loop-carried dependences with a distance of one
between a store and a load. Since it's using LoopAccessAnalysis, it was
easy to also add support for versioning away may-aliasing intervening
stores that would otherwise prevent this transformation.
This optimization is also performed by Load-PRE in GVN without the
option of multi-versioning. As was discussed with Daniel Berlin in
http://reviews.llvm.org/D9548, this is inferior to a more loop-aware
solution applied here. Hopefully, we will be able to remove some
complexity from GVN/MemorySSA as a consequence.
In the long run, we may want to extend this pass (or create a new one if
there is little overlap) to also eliminate loop-indepedent redundant
loads and store that *require* versioning due to may-aliasing
intervening stores/loads. I have some motivating cases for store
elimination. My plan right now is to wait for MemorySSA to come online
first rather than using memdep for this.
The main motiviation for this pass is the 456.hmmer loop in SPECint2006
where after distributing the original loop and vectorizing the top part,
we are left with the critical path exposed in the bottom loop. Being
able to promote the memory dependence into a register depedence (even
though the HW does perform store-to-load fowarding as well) results in a
major gain (~20%). This gain also transfers over to x86: it's
around 8-10%.
Right now the pass is off by default and can be enabled
with -enable-loop-load-elim. On the LNT testsuite, there are two
performance changes (negative number -> improvement):
1. -28% in Polybench/linear-algebra/solvers/dynprog: the length of the
critical paths is reduced
2. +2% in Polybench/stencils/adi: Unfortunately, I couldn't reproduce this
outside of LNT
The pass is scheduled after the loop vectorizer (which is after loop
distribution). The rational is to try to reuse LAA state, rather than
recomputing it. The order between LV and LLE is not critical because
normally LV does not touch scalar st->ld forwarding cases where
vectorizing would inhibit the CPU's st->ld forwarding to kick in.
LoopLoadElimination requires LAA to provide the full set of dependences
(including forward dependences). LAA is known to omit loop-independent
dependences in certain situations. The big comment before
removeDependencesFromMultipleStores explains why this should not occur
for the cases that we're interested in.
Reviewers: dberlin, hfinkel
Subscribers: junbuml, dberlin, mssimpso, rengolin, sanjoy, llvm-commits
Differential Revision: http://reviews.llvm.org/D13259
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252017 91177308-0d34-0410-b5e6-96231b3b80d8
Commit 251839 triggers miscompiles on some bots:
http://lab.llvm.org:8011/builders/perf-x86_64-penryn-O3-polly-fast/builds/13723
(The commit is listed in 13722, but due to an existing failure introduced in
13721 and reverted in 13723 the failure is only visible in 13723)
To verify r251839 is indeed the only change that triggered the buildbot failures
and to ensure the buildbots remain green while investigating I temporarily
revert this commit. At the current state it is unclear if this commit introduced
some miscompile or if it only exposed code to Polly that is subsequently
miscompiled by Polly.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251901 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
This patch adds support to check if a loop has loop invariant conditions which lead to loop exits. If so, we know that if the exit path is taken, it is at the first loop iteration. If there is an induction variable used in that exit path whose value has not been updated, it will keep its initial value passing from loop preheader. We can therefore rewrite the exit value with
its initial value. This will help remove phis created by LCSSA and enable other optimizations like loop unswitch.
Reviewers: sanjoy
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D13974
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251839 91177308-0d34-0410-b5e6-96231b3b80d8
Somewhat shockingly for an analysis pass which is computing constant ranges, LVI did not understand the ranges provided by range metadata.
As part of this change, I included a change to CVP primarily because doing so made it much easier to write small self contained test cases. CVP was previously only handling the non-local operand case, but given that LVI can sometimes figure out information about instructions standalone, I don't see any reason to restrict this. There could possibly be a compile time impact from this, but I suspect it should be minimal. If anyone has an example which substaintially regresses, please let me know. I could restrict the block local handling to ICmps feeding Terminator instructions if needed.
Note that this patch continues a somewhat bad practice in LVI. In many cases, we know facts about values, and separate context sensitive facts about values. LVI makes no effort to distinguish and will frequently cache the same value fact repeatedly for different contexts. I would like to change this, but that's a large enough change that I want it to go in separately with clear documentation of what's changing. Other examples of this include the non-null handling, and arguments.
As a meta comment: the entire motivation of this change was being able to write smaller (aka reasonable sized) test cases for a future patch teaching LVI about select instructions.
Differential Revision: http://reviews.llvm.org/D13543
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251606 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
If P branches to Q conditional on C and Q branches to R conditional on
C' and C => C' then the branch conditional on C' can be folded to an
unconditional branch.
Reviewers: reames
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D13972
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251557 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
This patch adds support to check if a loop has loop invariant conditions which lead to loop exits. If so, we know that if the exit path is taken, it is at the first loop iteration. If there is an induction variable used in that exit path whose value has not been updated, it will keep its initial value passing from loop preheader. We can therefore rewrite the exit value with
its initial value. This will help remove phis created by LCSSA and enable other optimizations like loop unswitch.
Reviewers: sanjoy
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D13974
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251492 91177308-0d34-0410-b5e6-96231b3b80d8
After some look-ahead PRE was added for GEPs, an instruction could end
up in the table of candidates before it was actually inspected. When
this happened the pass might decide it was the best candidate to
replace itself. This didn't go well.
Should fix PR25291
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251145 91177308-0d34-0410-b5e6-96231b3b80d8
The insertLoop() API is only used to add new loops, and has confusing
ownership semantics. Simplify it by replacing it with addLoop().
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251064 91177308-0d34-0410-b5e6-96231b3b80d8
As an invariant, BasicBlocks cannot be empty when passed to a transform.
This is not the case for MachineBasicBlocks and the Sink pass was ported
from the MachineSink pass which would explain the check's existence.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251057 91177308-0d34-0410-b5e6-96231b3b80d8
