If we know that the abs operand is known negative, we can replace
it with a neg.
To avoid computing known bits twice, I've removed the fold for the
non-negative case from InstSimplify. Both the non-negative and the
negative case are handled by InstCombine now, with one known bits call.
Differential Revision: https://reviews.llvm.org/D87196
This was supposed to be an NFC cleanup, but there's
a real logic difference (did not drop 'nsw') visible
in some tests in addition to an efficiency improvement.
This is because in the case where we have 2 GEPs,
the code was *always* swapping the operands and
negating the result. But if we have 2 GEPs, we
should *never* need swapping/negation AFAICT.
This is part of improving flags propagation noticed
with PR47430.
Normal dead code elimination ignores assume intrinsics, so we fail to
delete assumes that are not meaningful (and potentially worse if they
cause conflicts with other assumptions).
The motivating example in https://llvm.org/PR47416 suggests that we
might have problems upstream from here (difference between C and C++),
but this should be a cheap way to make sure we remove more dead code.
Differential Revision: https://reviews.llvm.org/D87149
Similar to D87168, but for abs. If we have a dominating x >= 0
condition, then we know that abs(x) is x. This fold is in
InstCombine, because we need to create a sub instruction for
the x < 0 case.
Differential Revision: https://reviews.llvm.org/D87184
These transforms will now be performed irrespective of the number of uses for the expression "1.0/sqrt(X)":
1.0/sqrt(X) * X => X/sqrt(X)
X * 1.0/sqrt(X) => X/sqrt(X)
We already handle more general cases, and we are intentionally not creating extra (and likely expensive)
fdiv ops in IR. This pattern is the exception to the rule because we always expect the Backend to reduce
X/sqrt(X) to sqrt(X), if it has the necessary (reassoc) fast-math-flags.
Ref: DagCombiner optimizes the X/sqrt(X) to sqrt(X).
Differential Revision: https://reviews.llvm.org/D86726
The original take 1 was 6102310d81,
which taught InstSimplify to do that, which seemed better at time,
since we got EarlyCSE support for free.
However, it was proven that we can not do that there,
the simplified-to PHI would not be reachable from the original PHI,
and that is not something InstSimplify is allowed to do,
as noted in the commit ed90f15efb
that reverted it:
> It appears to cause compilation non-determinism and caused stage3 mismatches.
Then there was take 2 3e69871ab5,
which was InstCombine-specific, but it again showed stage2-stage3 differences,
and reverted in bdaa3f86a0.
This is quite alarming.
Here, let's try to change how we find existing PHI candidate:
due to the worklist order, and the way PHI nodes are inserted
(it may be inserted as the first one, or maybe not), let's look at *all*
PHI nodes in the block.
Effects on vanilla llvm test-suite + RawSpeed:
```
| statistic name | baseline | proposed | Δ | % | \|%\| |
|----------------------------------------------------|-----------|-----------|-------:|---------:|---------:|
| asm-printer.EmittedInsts | 7942329 | 7942457 | 128 | 0.00% | 0.00% |
| assembler.ObjectBytes | 254295632 | 254312480 | 16848 | 0.01% | 0.01% |
| correlated-value-propagation.NumPhis | 18412 | 18347 | -65 | -0.35% | 0.35% |
| early-cse.NumCSE | 2183283 | 2183267 | -16 | 0.00% | 0.00% |
| early-cse.NumSimplify | 550105 | 541842 | -8263 | -1.50% | 1.50% |
| instcombine.NumAggregateReconstructionsSimplified | 73 | 4506 | 4433 | 6072.60% | 6072.60% |
| instcombine.NumCombined | 3640311 | 3644419 | 4108 | 0.11% | 0.11% |
| instcombine.NumDeadInst | 1778204 | 1783205 | 5001 | 0.28% | 0.28% |
| instcombine.NumPHICSEs | 0 | 22490 | 22490 | 0.00% | 0.00% |
| instcombine.NumWorklistIterations | 2023272 | 2024400 | 1128 | 0.06% | 0.06% |
| instcount.NumCallInst | 1758395 | 1758802 | 407 | 0.02% | 0.02% |
| instcount.NumInvokeInst | 59478 | 59502 | 24 | 0.04% | 0.04% |
| instcount.NumPHIInst | 330557 | 330545 | -12 | 0.00% | 0.00% |
| instcount.TotalBlocks | 1077138 | 1077220 | 82 | 0.01% | 0.01% |
| instcount.TotalFuncs | 101442 | 101441 | -1 | 0.00% | 0.00% |
| instcount.TotalInsts | 8831946 | 8832606 | 660 | 0.01% | 0.01% |
| simplifycfg.NumHoistCommonCode | 24186 | 24187 | 1 | 0.00% | 0.00% |
| simplifycfg.NumInvokes | 4300 | 4410 | 110 | 2.56% | 2.56% |
| simplifycfg.NumSimpl | 1019813 | 999767 | -20046 | -1.97% | 1.97% |
```
So it fires 22490 times, which is less than ~24k the take 1 did,
but more than what take 2 did (22228 times)
.
It allows foldAggregateConstructionIntoAggregateReuse() to actually work
after PHI-of-extractvalue folds did their thing. Previously SimplifyCFG
would have done this PHI CSE, of all places. Additionally, allows some
more `invoke`->`call` folds to happen (+110, +2.56%).
All in all, expectedly, this catches less things overall,
but all the motivational cases are still caught, so all good.
While the original variant with doing this in InstSimplify (rightfully)
caused questions and ultimately was detected to be a culprit
of stage2-stage3 mismatch, it was expected that
InstCombine-based implementation would be fine.
But apparently it's not, as
http://lab.llvm.org:8011/builders/clang-with-thin-lto-ubuntu/builds/24095/steps/compare-compilers/logs/stdio
suggests.
Which suggests that somewhere in InstCombine there is a loop
over nondeterministically sorted container, which causes
different worklist ordering.
This reverts commit 3e69871ab5.
As we've established, if it takes more than two iterations
(one to perform folding and one to ensure that no folding opportunities
remain) per function, then there are worklist management issues.
So it may be interesting to keep track of it.
The original take was 6102310d81,
which taught InstSimplify to do that, which seemed better at time,
since we got EarlyCSE support for free.
However, it was proven that we can not do that there,
the simplified-to PHI would not be reachable from the original PHI,
and that is not something InstSimplify is allowed to do,
as noted in the commit ed90f15efb
that reverted it :
> It appears to cause compilation non-determinism and caused stage3 mismatches.
However InstCombine already does many different optimizations,
so it should be a safe place to do it here.
Note that we still can't just compare incoming values ranges,
because there is no guarantee that these PHI's we'd simplify to
were already re-visited and sorted.
However coming up with a test is problematic.
Effects on vanilla llvm test-suite + RawSpeed:
```
| statistic name | baseline | proposed | Δ | % | |%| |
|----------------------------------------------------|-----------|-----------|-------:|---------:|---------:|
| instcombine.NumPHICSEs | 0 | 22228 | 22228 | 0.00% | 0.00% |
| asm-printer.EmittedInsts | 7942329 | 7942456 | 127 | 0.00% | 0.00% |
| assembler.ObjectBytes | 254295632 | 254313792 | 18160 | 0.01% | 0.01% |
| early-cse.NumCSE | 2183283 | 2183272 | -11 | 0.00% | 0.00% |
| early-cse.NumSimplify | 550105 | 541842 | -8263 | -1.50% | 1.50% |
| instcombine.NumAggregateReconstructionsSimplified | 73 | 4506 | 4433 | 6072.60% | 6072.60% |
| instcombine.NumCombined | 3640311 | 3666911 | 26600 | 0.73% | 0.73% |
| instcombine.NumDeadInst | 1778204 | 1783318 | 5114 | 0.29% | 0.29% |
| instcount.NumCallInst | 1758395 | 1758804 | 409 | 0.02% | 0.02% |
| instcount.NumInvokeInst | 59478 | 59502 | 24 | 0.04% | 0.04% |
| instcount.NumPHIInst | 330557 | 330549 | -8 | 0.00% | 0.00% |
| instcount.TotalBlocks | 1077138 | 1077221 | 83 | 0.01% | 0.01% |
| instcount.TotalFuncs | 101442 | 101441 | -1 | 0.00% | 0.00% |
| instcount.TotalInsts | 8831946 | 8832611 | 665 | 0.01% | 0.01% |
| simplifycfg.NumInvokes | 4300 | 4410 | 110 | 2.56% | 2.56% |
| simplifycfg.NumSimpl | 1019813 | 999740 | -20073 | -1.97% | 1.97% |
```
So it fires ~22k times, which is less than ~24k the take 1 did.
It allows foldAggregateConstructionIntoAggregateReuse() to actually work
after PHI-of-extractvalue folds did their thing. Previously SimplifyCFG
would have done this PHI CSE, of all places. Additionally, allows some
more `invoke`->`call` folds to happen (+110, +2.56%).
All in all, expectedly, this catches less things overall,
but all the motivational cases are still caught, so all good.
This patch changes ElementCount so that the Min and Scalable
members are now private and can only be accessed via the get
functions getKnownMinValue() and isScalable(). In addition I've
added some other member functions for more commonly used operations.
Hopefully this makes the class more useful and will reduce the
need for calling getKnownMinValue().
Differential Revision: https://reviews.llvm.org/D86065
As FIXME said, they really should be checking for a single user,
not use, so let's do that. It is not *that* unusual to have
the same value as incoming value in a PHI node, not unlike
how a PHI may have the same incoming basic block more than once.
There isn't a nice way to do that, Value::users() isn't uniqified,
and Value only tracks it's uses, not Users, so the check is
potentially costly since it does indeed potentially involes
traversing the entire use list of a value.
While since D86306 we do it's sibling fold for `insertvalue`,
we should also do this for `extractvalue`'s.
And unlike that one, the results here are, quite honestly, shocking,
as it can be observed here on vanilla llvm test-suite + RawSpeed results:
```
| statistic name | baseline | proposed | Δ | % | |%| |
|----------------------------------------------------|-----------|-----------|--------:|--------:|-------:|
| asm-printer.EmittedInsts | 7945095 | 7942507 | -2588 | -0.03% | 0.03% |
| assembler.ObjectBytes | 273209920 | 273069800 | -140120 | -0.05% | 0.05% |
| early-cse.NumCSE | 2183363 | 2183398 | 35 | 0.00% | 0.00% |
| early-cse.NumSimplify | 541847 | 550017 | 8170 | 1.51% | 1.51% |
| instcombine.NumAggregateReconstructionsSimplified | 2139 | 108 | -2031 | -94.95% | 94.95% |
| instcombine.NumCombined | 3601364 | 3635448 | 34084 | 0.95% | 0.95% |
| instcombine.NumConstProp | 27153 | 27157 | 4 | 0.01% | 0.01% |
| instcombine.NumDeadInst | 1694521 | 1765022 | 70501 | 4.16% | 4.16% |
| instcombine.NumPHIsOfExtractValues | 0 | 37546 | 37546 | 0.00% | 0.00% |
| instcombine.NumSunkInst | 63158 | 63686 | 528 | 0.84% | 0.84% |
| instcount.NumBrInst | 874304 | 871857 | -2447 | -0.28% | 0.28% |
| instcount.NumCallInst | 1757657 | 1758402 | 745 | 0.04% | 0.04% |
| instcount.NumExtractValueInst | 45623 | 11483 | -34140 | -74.83% | 74.83% |
| instcount.NumInsertValueInst | 4983 | 580 | -4403 | -88.36% | 88.36% |
| instcount.NumInvokeInst | 61018 | 59478 | -1540 | -2.52% | 2.52% |
| instcount.NumLandingPadInst | 35334 | 34215 | -1119 | -3.17% | 3.17% |
| instcount.NumPHIInst | 344428 | 331116 | -13312 | -3.86% | 3.86% |
| instcount.NumRetInst | 100773 | 100772 | -1 | 0.00% | 0.00% |
| instcount.TotalBlocks | 1081154 | 1077166 | -3988 | -0.37% | 0.37% |
| instcount.TotalFuncs | 101443 | 101442 | -1 | 0.00% | 0.00% |
| instcount.TotalInsts | 8890201 | 8833747 | -56454 | -0.64% | 0.64% |
| instsimplify.NumSimplified | 75822 | 75707 | -115 | -0.15% | 0.15% |
| simplifycfg.NumHoistCommonCode | 24203 | 24197 | -6 | -0.02% | 0.02% |
| simplifycfg.NumHoistCommonInstrs | 48201 | 48195 | -6 | -0.01% | 0.01% |
| simplifycfg.NumInvokes | 2785 | 4298 | 1513 | 54.33% | 54.33% |
| simplifycfg.NumSimpl | 997332 | 1018189 | 20857 | 2.09% | 2.09% |
| simplifycfg.NumSinkCommonCode | 7088 | 6464 | -624 | -8.80% | 8.80% |
| simplifycfg.NumSinkCommonInstrs | 15117 | 14021 | -1096 | -7.25% | 7.25% |
```
... which tells us that this new fold fires whopping 38k times,
increasing the amount of SimplifyCFG's `invoke`->`call` transforms by +54% (+1513) (again, D85787 did that last time),
decreasing total instruction count by -0.64% (-56454),
and sharply decreasing count of `insertvalue`'s (-88.36%, i.e. 9 times less)
and `extractvalue`'s (-74.83%, i.e. four times less).
This causes geomean -0.01% binary size decrease
http://llvm-compile-time-tracker.com/compare.php?from=4d5ca22b8adfb6643466e4e9f48ba14bb48938bc&to=97dacca0111cb2ae678204e52a3cee00e3a69208&stat=size-text
and, ignoring `O0-g`, is a geomean -0.01%..-0.05% compile-time improvement
http://llvm-compile-time-tracker.com/compare.php?from=4d5ca22b8adfb6643466e4e9f48ba14bb48938bc&to=97dacca0111cb2ae678204e52a3cee00e3a69208&stat=instructions
The other thing that tells is, is that while this is a massive win for `invoke`->`call` transform
`InstCombinerImpl::foldAggregateConstructionIntoAggregateReuse()` fold,
which is supposed to be dealing with such aggregate reconstructions,
fires a lot less now. There are two reasons why:
1. After this fold, as it can be seen in tests, we may (will) end up with trivially redundant PHI nodes.
We don't CSE them in InstCombine presently, which means that EarlyCSE needs to run and then InstCombine rerun.
2. But then, EarlyCSE not only manages to fold such redundant PHI's,
it also sees that the extract-insert chain recreates the original aggregate,
and replaces it with the original aggregate.
The take-aways are
1. We maybe should do most trivial, same-BB PHI CSE in InstCombine
2. I need to check if what other patterns remain, and how they can be resolved.
(i.e. i wonder if `foldAggregateConstructionIntoAggregateReuse()` might go away)
This is a reland of the original commit fcb51d8c24,
because originally i forgot to ensure that the base aggregate types match.
Reviewed By: spatel
Differential Revision: https://reviews.llvm.org/D86530
This reverts commit fcb51d8c24.
As buildbots report, there's apparently some missing check to ensure
that the types of incoming values match the type of PHI.
Let's revert for a moment.
While since D86306 we do it's sibling fold for `insertvalue`,
we should also do this for `extractvalue`'s.
And unlike that one, the results here are, quite honestly, shocking,
as it can be observed here on vanilla llvm test-suite + RawSpeed results:
```
| statistic name | baseline | proposed | Δ | % | |%| |
|----------------------------------------------------|-----------|-----------|--------:|--------:|-------:|
| asm-printer.EmittedInsts | 7945095 | 7942507 | -2588 | -0.03% | 0.03% |
| assembler.ObjectBytes | 273209920 | 273069800 | -140120 | -0.05% | 0.05% |
| early-cse.NumCSE | 2183363 | 2183398 | 35 | 0.00% | 0.00% |
| early-cse.NumSimplify | 541847 | 550017 | 8170 | 1.51% | 1.51% |
| instcombine.NumAggregateReconstructionsSimplified | 2139 | 108 | -2031 | -94.95% | 94.95% |
| instcombine.NumCombined | 3601364 | 3635448 | 34084 | 0.95% | 0.95% |
| instcombine.NumConstProp | 27153 | 27157 | 4 | 0.01% | 0.01% |
| instcombine.NumDeadInst | 1694521 | 1765022 | 70501 | 4.16% | 4.16% |
| instcombine.NumPHIsOfExtractValues | 0 | 37546 | 37546 | 0.00% | 0.00% |
| instcombine.NumSunkInst | 63158 | 63686 | 528 | 0.84% | 0.84% |
| instcount.NumBrInst | 874304 | 871857 | -2447 | -0.28% | 0.28% |
| instcount.NumCallInst | 1757657 | 1758402 | 745 | 0.04% | 0.04% |
| instcount.NumExtractValueInst | 45623 | 11483 | -34140 | -74.83% | 74.83% |
| instcount.NumInsertValueInst | 4983 | 580 | -4403 | -88.36% | 88.36% |
| instcount.NumInvokeInst | 61018 | 59478 | -1540 | -2.52% | 2.52% |
| instcount.NumLandingPadInst | 35334 | 34215 | -1119 | -3.17% | 3.17% |
| instcount.NumPHIInst | 344428 | 331116 | -13312 | -3.86% | 3.86% |
| instcount.NumRetInst | 100773 | 100772 | -1 | 0.00% | 0.00% |
| instcount.TotalBlocks | 1081154 | 1077166 | -3988 | -0.37% | 0.37% |
| instcount.TotalFuncs | 101443 | 101442 | -1 | 0.00% | 0.00% |
| instcount.TotalInsts | 8890201 | 8833747 | -56454 | -0.64% | 0.64% |
| instsimplify.NumSimplified | 75822 | 75707 | -115 | -0.15% | 0.15% |
| simplifycfg.NumHoistCommonCode | 24203 | 24197 | -6 | -0.02% | 0.02% |
| simplifycfg.NumHoistCommonInstrs | 48201 | 48195 | -6 | -0.01% | 0.01% |
| simplifycfg.NumInvokes | 2785 | 4298 | 1513 | 54.33% | 54.33% |
| simplifycfg.NumSimpl | 997332 | 1018189 | 20857 | 2.09% | 2.09% |
| simplifycfg.NumSinkCommonCode | 7088 | 6464 | -624 | -8.80% | 8.80% |
| simplifycfg.NumSinkCommonInstrs | 15117 | 14021 | -1096 | -7.25% | 7.25% |
```
... which tells us that this new fold fires whopping 38k times,
increasing the amount of SimplifyCFG's `invoke`->`call` transforms by +54% (+1513) (again, D85787 did that last time),
decreasing total instruction count by -0.64% (-56454),
and sharply decreasing count of `insertvalue`'s (-88.36%, i.e. 9 times less)
and `extractvalue`'s (-74.83%, i.e. four times less).
This causes geomean -0.01% binary size decrease
http://llvm-compile-time-tracker.com/compare.php?from=4d5ca22b8adfb6643466e4e9f48ba14bb48938bc&to=97dacca0111cb2ae678204e52a3cee00e3a69208&stat=size-text
and, ignoring `O0-g`, is a geomean -0.01%..-0.05% compile-time improvement
http://llvm-compile-time-tracker.com/compare.php?from=4d5ca22b8adfb6643466e4e9f48ba14bb48938bc&to=97dacca0111cb2ae678204e52a3cee00e3a69208&stat=instructions
The other thing that tells is, is that while this is a massive win for `invoke`->`call` transform
`InstCombinerImpl::foldAggregateConstructionIntoAggregateReuse()` fold,
which is supposed to be dealing with such aggregate reconstructions,
fires a lot less now. There are two reasons why:
1. After this fold, as it can be seen in tests, we may (will) end up with trivially redundant PHI nodes.
We don't CSE them in InstCombine presently, which means that EarlyCSE needs to run and then InstCombine rerun.
2. But then, EarlyCSE not only manages to fold such redundant PHI's,
it also sees that the extract-insert chain recreates the original aggregate,
and replaces it with the original aggregate.
The take-aways are
1. We maybe should do most trivial, same-BB PHI CSE in InstCombine
2. I need to check if what other patterns remain, and how they can be resolved.
(i.e. i wonder if `foldAggregateConstructionIntoAggregateReuse()` might go away)
Reviewed By: spatel
Differential Revision: https://reviews.llvm.org/D86530
The 1st attempt (rG557b890) was reverted because it caused miscompiles.
That bug is avoided here by changing the order of folds and as verified
in the new tests.
Original commit message:
InstCombine currently has odd rules for folding insert-extract chains to shuffles,
so we miss collapsing seemingly simple cases as shown in the tests here.
But poison makes this not quite as easy as we might have guessed. Alive2 tests to
show the subtle difference (similar to the regression tests):
https://alive2.llvm.org/ce/z/hp4hv3 (this is ok)
https://alive2.llvm.org/ce/z/ehEWaN (poison leakage)
SLP tends to create these patterns (as shown in the SLP tests), and this could
help with solving PR16739.
Differential Revision: https://reviews.llvm.org/D86460
In getCastInstrCost when the instruction is a truncate we were relying
upon the implicit TypeSize -> uint64_t cast when asking if a given type
has the same size as a legal integer. I've changed the code to only
ask the question if the type is fixed length.
I have also changed InstCombinerImpl::SimplifyDemandedUseBits to bail
out for now if the type is a scalable vector.
I've added the following new tests:
Analysis/CostModel/AArch64/sve-trunc.ll
Transforms/InstCombine/AArch64/sve-trunc.ll
for both of these fixes.
Differential revision: https://reviews.llvm.org/D86432
InstCombine currently has odd rules for folding insert-extract chains to shuffles,
so we miss collapsing seemingly simple cases as shown in the tests here.
But poison makes this not quite as easy as we might have guessed. Alive2 tests to
show the subtle difference (similar to the regression tests):
https://alive2.llvm.org/ce/z/hp4hv3 (this is ok)
https://alive2.llvm.org/ce/z/ehEWaN (poison leakage)
SLP tends to create these patterns (as shown in the SLP tests), and this could
help with solving PR16739.
Differential Revision: https://reviews.llvm.org/D86460
Similar to the existing transform - peek through a select
to match a value and its negation.
https://alive2.llvm.org/ce/z/MXi5KG
define i8 @src(i1 %b, i8 %x) {
%0:
%neg = sub i8 0, %x
%sel = select i1 %b, i8 %x, i8 %neg
%abs = abs i8 %sel, 1
ret i8 %abs
}
=>
define i8 @tgt(i1 %b, i8 %x) {
%0:
%abs = abs i8 %x, 1
ret i8 %abs
}
Transformation seems to be correct!
This reverses the existing transform that would uniformly canonicalize any 'xor' after any shift. In the case of logical shifts, that turns a 'not' into an arbitrary 'xor' with constant, and that's probably not as good for analysis, SCEV, or codegen.
The SCEV motivating case is discussed in:
http://bugs.llvm.org/PR47136
There's an analysis motivating case at:
http://bugs.llvm.org/PR38781
I did draft a patch that would do the same for 'ashr' but that's questionable because it's just swapping the position of a 'not' and uncovers at least 2 missing folds that we would probably need to deal with as preliminary steps.
Alive proofs:
https://rise4fun.com/Alive/BBV
Name: shift right of 'not'
Pre: C2 == (-1 u>> C1)
%a = lshr i8 %x, C1
%r = xor i8 %a, C2
=>
%n = xor i8 %x, -1
%r = lshr i8 %n, C1
Name: shift left of 'not'
Pre: C2 == (-1 << C1)
%a = shl i8 %x, C1
%r = xor i8 %a, C2
=>
%n = xor i8 %x, -1
%r = shl i8 %n, C1
Name: ashr of 'not'
%a = ashr i8 %x, C1
%r = xor i8 %a, -1
=>
%n = xor i8 %x, -1
%r = ashr i8 %n, C1
Differential Revision: https://reviews.llvm.org/D86243
If some of gc live value are not used in gc.relocate we can remove them
from gc-live bundle of statepoint instruction.
Also the CL removes duplicated Values in gc-live bundle.
Reviewers: reames, dantrushin
Reviewed By: dantrushin
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D85959
The only def for gc.relocate is a gc.statepoint. But real dependency is not
described by def-use chain. Instead this dependency is encoded by indecies
of operands in gc-live bundle of statepoint as integer constants in gc.relocate.
InstCombine operates by def-use chain. As a result when value in gc-live bundle
is simplified the gc.statepoint itself is not simplified but it might simplify dependent
gc.relocates. To trigger the optimization of gc.relocate we now unconditionally trigger
check of all dependent gc.relocates by adding them to worklist.
This CL handles of gc.relocates as process of gc.statepoint optimization considering
gc.statepoint and related gc.relocate as whole entity.
Reviewers: reames, dantrushin
Reviewed By: reames
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D85954
There's a potential motivating case to increase this limit in PR47191:
http://bugs.llvm.org/PR47191
But first we should make it less hacky. The limit in InstCombine is directly tied
to this value because an increase there can cause asserts in the underlying value
tracking calls if not changed together. The usage in VectorUtils is independent,
but the comment suggests that we should use the same value unless there's a known
reason to diverge. There are similar limits in codegen analysis, but I think we
should leave those independent in case we intentionally want the optimization
power/cost to be different there.
Differential Revision: https://reviews.llvm.org/D86113
And as being reported by Florian Hahn, there's a hit
in MultiSource/Benchmarks/mafft from the test-suite on X86 with -O3 -flto,
so reverting until addressed.
This reverts commit 71e0b82c9f.
Now that we no longer require for this map to have stable iteration order,
we no longer need to pay for keeping the iteration order stable,
so switch from `SmallMapVector` to `SmallDenseMap`.
While it may seem like we can just "deduplicate" the case where
some basic block happens to be a predecessor more than once,
which happens for e.g. switches, that is not correct thing to do.
We must actually add a PHI operand for each predecessor.
This was initially reported to me by David Major
as a clang crash during gecko build for android.
Nikita Popov