| Commit message (Collapse) | Author | Age | Files | Lines |
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fcmp+select
As noted by the FIXME comment, this is not correct based on our current FMF semantics.
We should be propagating FMF from the final value in a sequence (in this case the
'select'). So the behavior even without this patch is wrong, but we did not allow FMF
on 'select' until recently.
But if we do the correct thing right now in this patch, we'll inevitably introduce
regressions because we have not wired up FMF propagation for 'phi' and 'select' in
other passes (like SimplifyCFG) or other places in InstCombine. I'm not seeing a
better incremental way to make progress.
That said, the potential extra damage over the existing wrong behavior from this
patch is very limited. AFAIK, the only way to have different FMF on IR in the same
function is if we have LTO inlined IR from 2 modules that were compiled using
different fast-math settings.
As seen in the tests, we may actually see some improvements with this patch because
adding the FMF to the 'select' allows matching to min/max intrinsics that were
previously missed (in the common case, the 'fcmp' and 'select' should have identical
FMF to begin with).
Next steps in the transition:
Make similar changes in instcombine as needed.
Enable phi-to-select FMF propagation in SimplifyCFG.
Remove dependencies on fcmp with FMF.
Deprecate FMF on fcmp.
Differential Revision: https://reviews.llvm.org/D69720
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Avoid subsequent test noise from improved CHECK-LABEL matching.
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This has the potential to uncover missed analysis/folds as shown in the
min/max code comment/test, but fewer restrictions on icmp folds should
be better in general to solve cases like:
https://bugs.llvm.org/show_bug.cgi?id=43310
llvm-svn: 372510
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The reversion apparently deleted the test/Transforms directory.
Will be re-reverting again.
llvm-svn: 358552
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As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
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This is D59386 for the signed add case. The computeConstantRange()
result is now intersected into the existing known bits information,
allowing to detect additional no-overflow/always-overflow conditions
(though the latter isn't used yet).
This (finally...) covers the motivating case from D59071.
Differential Revision: https://reviews.llvm.org/D60420
llvm-svn: 358014
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Add support for min/max flavor selects in computeConstantRange(),
which allows us to fold comparisons of a min/max against a constant
in InstSimplify. This fixes an infinite InstCombine loop, with the
test case taken from D59378.
Relative to the previous iteration, this contains some adjustments for
AMDGPU med3 tests: The AMDGPU target runs InstSimplify prior to codegen,
which ends up constant folding some existing med3 tests after this
change. To preserve these tests a hidden -amdgpu-scalar-ir-passes option
is added, which allows disabling scalar IR passes (that use InstSimplify)
for testing purposes.
Differential Revision: https://reviews.llvm.org/D59506
llvm-svn: 357870
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This is the last step towards solving the examples shown in:
https://bugs.llvm.org/show_bug.cgi?id=14613
With this change, x86 should end up with psubus instructions
when those are available.
All known codegen issues with expanding the saturating intrinsics
were resolved with:
D59006 / rL356855
We also have some early evidence in D58872 that using the intrinsics
will lead to better perf. If some target regresses from this, custom
lowering of the intrinsics (as in the above for x86) may be needed.
llvm-svn: 357012
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computeConstantRange()"
This reverts commit 106f0cdefb02afc3064268dc7a71419b409ed2f3.
This change impacts the AMDGPU smed3.ll and umed3.ll codegen tests.
llvm-svn: 356424
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Add support for min/max flavor selects in computeConstantRange(),
which allows us to fold comparisons of a min/max against a constant
in InstSimplify. This was suggested by spatel as an alternative
approach to D59378. I've also added the infinite looping test from
that revision here.
Differential Revision: https://reviews.llvm.org/D59506
llvm-svn: 356415
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Follow-up to rL355221.
This isn't specifically called for within PR14613,
but we'll get there eventually if it's not already
requested in some other bug report.
https://rise4fun.com/Alive/5b0
Name: smax
Pre: WillNotOverflowSignedSub(C1,C0)
%a = add nsw i8 %x, C0
%cond = icmp sgt i8 %a, C1
%r = select i1 %cond, i8 %a, i8 C1
=>
%c2 = icmp sgt i8 %x, C1-C0
%u2 = select i1 %c2, i8 %x, i8 C1-C0
%r = add nsw i8 %u2, C0
Name: smin
Pre: WillNotOverflowSignedSub(C1,C0)
%a = add nsw i32 %x, C0
%cond = icmp slt i32 %a, C1
%r = select i1 %cond, i32 %a, i32 C1
=>
%c2 = icmp slt i32 %x, C1-C0
%u2 = select i1 %c2, i32 %x, i32 C1-C0
%r = add nsw i32 %u2, C0
llvm-svn: 355272
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llvm-svn: 355271
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In the motivating cases from PR14613:
https://bugs.llvm.org/show_bug.cgi?id=14613
...moving the add enables us to narrow the
min/max which eliminates zext/trunc which
enables signficantly better vectorization.
But that bug is still not completely fixed.
https://rise4fun.com/Alive/5KQ
Name: umax
Pre: C1 u>= C0
%a = add nuw i8 %x, C0
%cond = icmp ugt i8 %a, C1
%r = select i1 %cond, i8 %a, i8 C1
=>
%c2 = icmp ugt i8 %x, C1-C0
%u2 = select i1 %c2, i8 %x, i8 C1-C0
%r = add nuw i8 %u2, C0
Name: umin
Pre: C1 u>= C0
%a = add nuw i32 %x, C0
%cond = icmp ult i32 %a, C1
%r = select i1 %cond, i32 %a, i32 C1
=>
%c2 = icmp ult i32 %x, C1-C0
%u2 = select i1 %c2, i32 %x, i32 C1-C0
%r = add nuw i32 %u2, C0
llvm-svn: 355221
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llvm-svn: 355220
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Fixing this should solve the biggest part of the vector problems seen in:
https://bugs.llvm.org/show_bug.cgi?id=14613
llvm-svn: 355206
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This is the planned enhancement to D47163 / rL333611.
We want to match cmp/select sizes because that will be recognized
as min/max more easily and lead to better codegen (especially for
vector types).
As mentioned in D47163, this improves some of the tests that would
also be folded by D46380, so we may want to adjust that patch to
match the new patterns where the extend op occurs after the select.
llvm-svn: 333689
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llvm-svn: 333682
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The test is derived from a failing fuzz test:
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=5008
Credit to @rksimon for pointing out the problem.
llvm-svn: 322016
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There is precedence for factorization transforms in instcombine for FP ops with fast-math.
We also have similar logic in foldSPFofSPF().
It would take more work to add this to reassociate because that's specialized for binops,
and min/max are not binops (or even single instructions). Also, I don't have evidence that
larger min/max trees than this exist in real code, but if we find that's true, we might
want to reorganize where/how we do this optimization.
In the motivating example from https://bugs.llvm.org/show_bug.cgi?id=35717 , we have:
int test(int xc, int xm, int xy) {
int xk;
if (xc < xm)
xk = xc < xy ? xc : xy;
else
xk = xm < xy ? xm : xy;
return xk;
}
This patch solves that problem because we recognize more min/max patterns after rL321672
https://rise4fun.com/Alive/Qjne
https://rise4fun.com/Alive/3yg
Differential Revision: https://reviews.llvm.org/D41603
llvm-svn: 321998
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llvm-svn: 321500
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Summary:
ValueTracking was recognizing not all variations of clamp. Swapping of
true value and false value of select was added to fix this problem. The
first patch was reverted because it caused miscompile in NVPTX target.
Added corresponding test cases.
Reviewers: spatel, majnemer, efriedma, reames
Subscribers: llvm-commits, jholewinski
Differential Revision: https://reviews.llvm.org/D39240
llvm-svn: 316795
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llvm-svn: 316322
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llvm-svn: 316164
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Summary:
When we have the following case:
%cond = cmp iN %x, CmpConst
%tr = trunc iN %x to iK
%narrowsel = select i1 %cond, iK %t, iK C
We could possibly match only min/max pattern after looking through cast.
So it is more profitable if widened C constant will be equal CmpConst.
That is why just set widened C constant equal to CmpConst, because there
is a further check in this function that trunc CmpConst == C.
Also description for lookTroughCast function was added.
Reviewers: spatel
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D38536
Patch by: Artur Gainullin <artur.gainullin@intel.com>
llvm-svn: 316070
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Summary:
ValueTracking was recognizing not all variations of clamp. Swapping of
true value and false value of select was added to fix this problem. This
change breaks the canonical form of cmp inside the matchMinMax function,
that is why additional checks for compare predicates is needed. Added
corresponding test cases.
Reviewers: spatel
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D38531
Patch by: Artur Gainullin <artur.gainullin@intel.com>
llvm-svn: 315992
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Summary:
The following transformation for cmp instruction:
icmp smin(x, PositiveValue), 0 -> icmp x, 0
should only be done after checking for min/max to prevent infinite
looping caused by a reverse canonicalization. That is why this
transformation was moved to place after the mentioned check.
Reviewers: spatel, efriedma
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D38934
Patch by: Artur Gainullin <artur.gainullin@intel.com>
llvm-svn: 315895
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llvm-svn: 315461
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Summary:
This commit allows matchSelectPattern to recognize clamp of float
arguments in the presence of FMF the same way as already done for
integers.
This case is a little different though. With integers, given the
min/max pattern is recognized, DAGBuilder starts selecting MIN/MAX
"automatically". That is not the case for float, because for them only
full FMINNAN/FMINNUM/FMAXNAN/FMAXNUM ISD nodes exist and they do care
about NaNs. On the other hand, some backends (e.g. X86) have only
FMIN/FMAX nodes that do not care about NaNS and the former NAN/NUM
nodes are illegal thus selection is not happening. So I decided to do
such kind of transformation in IR (InstCombiner) instead of
complicating the logic in the backend.
Reviewers: spatel, jmolloy, majnemer, efriedma, craig.topper
Reviewed By: efriedma
Subscribers: hiraditya, javed.absar, n.bozhenov, llvm-commits
Patch by Andrei Elovikov <andrei.elovikov@intel.com>
Differential Revision: https://reviews.llvm.org/D33186
llvm-svn: 310054
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Summary:
- add more tests
- pr27236.ll: rename %tmpN -> %N because otherwise a FileCheck
variable for newly appeared unnamed value would use the same name as
tmpN (as generated by update_test_checks.py)
- run update_test_checks.py
Reviewers: efriedma
Reviewed By: efriedma
Subscribers: n.bozhenov, llvm-commits
Patch by Andrei Elovikov <andrei.elovikov@intel.com>
Differential Revision: https://reviews.llvm.org/D35002
llvm-svn: 310053
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We can simplify (and (icmp X, C1), (icmp X, C2)) to one of the icmps in many cases.
I had to check some of these with Alive to prove to myself it's right, but everything
seems to check out. Eg, the code in instcombine was completely ignoring predicates with
mismatched signedness.
Handling or-of-icmps would be a follow-up step.
Differential Revision: https://reviews.llvm.org/D32143
llvm-svn: 301260
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As the related tests show, we're not canonicalizing to this form for scalars or vectors yet,
but this solves the immediate problem in:
https://bugs.llvm.org/show_bug.cgi?id=32306
llvm-svn: 297989
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llvm-svn: 297986
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inf-loop (PR31751)
This is a minimal patch to avoid the infinite loop in:
https://llvm.org/bugs/show_bug.cgi?id=31751
But the general problem is bigger: we're not canonicalizing all of the min/max forms reported
by value tracking's matchSelectPattern(), and we don't define min/max consistently. Some code
uses matchSelectPattern(), other code uses matchers like m_Umax, and others have their own
inline definitions which may be subtly different from any of the above.
The reason that the test cases in this patch need a cast op to trigger is because we don't
(yet) canonicalize all min/max forms based on matchSelectPattern() in
canonicalizeMinMaxWithConstant(), but we do make min/max+cast transforms based on
matchSelectPattern() in visitSelectInst().
The location of the icmp transforms that trigger the inf-loop seems arbitrary at best, so
I'm moving those behind the min/max fence in visitICmpInst() as the quick fix.
llvm-svn: 293345
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By enhancing value tracking, we allow an existing min/max canonicalization to
kick in and improve codegen for several targets that have min/max instructions.
Unfortunately, recognizing min/max in value tracking may cause us to hit
a hack in InstCombiner::visitICmpInst() more often:
http://lists.llvm.org/pipermail/llvm-dev/2017-January/109340.html
...but I'm hoping we can remove that soon.
Correctness proofs based on Alive:
Name: smaxmin
Pre: C1 < C2
%cmp2 = icmp slt i8 %x, C2
%min = select i1 %cmp2, i8 %x, i8 C2
%cmp3 = icmp slt i8 %x, C1
%r = select i1 %cmp3, i8 C1, i8 %min
=>
%cmp2 = icmp slt i8 %x, C2
%min = select i1 %cmp2, i8 %x, i8 C2
%cmp1 = icmp sgt i8 %min, C1
%r = select i1 %cmp1, i8 %min, i8 C1
Name: sminmax
Pre: C1 > C2
%cmp2 = icmp sgt i8 %x, C2
%max = select i1 %cmp2, i8 %x, i8 C2
%cmp3 = icmp sgt i8 %x, C1
%r = select i1 %cmp3, i8 C1, i8 %max
=>
%cmp2 = icmp sgt i8 %x, C2
%max = select i1 %cmp2, i8 %x, i8 C2
%cmp1 = icmp slt i8 %max, C1
%r = select i1 %cmp1, i8 %max, i8 C1
----------------------------------------
Optimization: smaxmin
Done: 1
Optimization is correct!
----------------------------------------
Optimization: sminmax
Done: 1
Optimization is correct!
Name: umaxmin
Pre: C1 u< C2
%cmp2 = icmp ult i8 %x, C2
%min = select i1 %cmp2, i8 %x, i8 C2
%cmp3 = icmp ult i8 %x, C1
%r = select i1 %cmp3, i8 C1, i8 %min
=>
%cmp2 = icmp ult i8 %x, C2
%min = select i1 %cmp2, i8 %x, i8 C2
%cmp1 = icmp ugt i8 %min, C1
%r = select i1 %cmp1, i8 %min, i8 C1
Name: uminmax
Pre: C1 u> C2
%cmp2 = icmp ugt i8 %x, C2
%max = select i1 %cmp2, i8 %x, i8 C2
%cmp3 = icmp ugt i8 %x, C1
%r = select i1 %cmp3, i8 C1, i8 %max
=>
%cmp2 = icmp ugt i8 %x, C2
%max = select i1 %cmp2, i8 %x, i8 C2
%cmp1 = icmp ult i8 %max, C1
%r = select i1 %cmp1, i8 %max, i8 C1
----------------------------------------
Optimization: umaxmin
Done: 1
Optimization is correct!
----------------------------------------
Optimization: uminmax
Done: 1
Optimization is correct!
llvm-svn: 292660
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Unfortunately, recognizing these in value tracking may cause us to hit
a hack in InstCombiner::visitICmpInst() more often:
http://lists.llvm.org/pipermail/llvm-dev/2017-January/109340.html
...but besides being the obviously Right Thing To Do, there's a clear
codegen win from identifying these patterns for several targets.
llvm-svn: 292655
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This is a first step towards canonicalization and improved folding/codegen
for integer min/max as discussed here:
http://lists.llvm.org/pipermail/llvm-dev/2016-November/106868.html
Here, we're just matching the simplest min/max patterns and adjusting the
icmp predicate while swapping the select operands.
I've included FIXME tests in test/Transforms/InstCombine/select_meta.ll
so it's easier to see how this might be extended (corresponds to the TODO
comment in the code). That's also why I'm using matchSelectPattern()
rather than a simpler check; once the backend is patched, we can just
remove some of the restrictions to allow the obfuscated min/max patterns
in the FIXME tests to be matched.
Differential Revision: https://reviews.llvm.org/D26525
llvm-svn: 287585
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llvm-svn: 286256
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These mixed bitcast patterns show up with SSE/AVX intrinsics because we bitcast function parameters to <2 x i64>.
The bitcasts obfuscate the expected min/max forms as shown in PR28001:
https://llvm.org/bugs/show_bug.cgi?id=28001#c6
Differential Revision: https://reviews.llvm.org/D25943
llvm-svn: 285495
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Accidentally put in the hoped-for checks ahead of the transform!
llvm-svn: 285070
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llvm-svn: 285069
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llvm-svn: 285046
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Make sure if we're truncating a constant that would then be sign extended
that the sign extension of the truncated constant is the same as the
original constant.
> Canonicalize min/max expressions correctly.
>
> This patch introduces a canonical form for min/max idioms where one operand
> is extended or truncated. This often happens when the other operand is a
> constant. For example:
>
> %1 = icmp slt i32 %a, i32 0
> %2 = sext i32 %a to i64
> %3 = select i1 %1, i64 %2, i64 0
>
> Would now be canonicalized into:
>
> %1 = icmp slt i32 %a, i32 0
> %2 = select i1 %1, i32 %a, i32 0
> %3 = sext i32 %2 to i64
>
> This builds upon a patch posted by David Majenemer
> (https://www.marc.info/?l=llvm-commits&m=143008038714141&w=2). That pass
> passively stopped instcombine from ruining canonical patterns. This
> patch additionally actively makes instcombine canonicalize too.
>
> Canonicalization of expressions involving a change in type from int->fp
> or fp->int are not yet implemented.
llvm-svn: 237821
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This caused PR23583.
llvm-svn: 237739
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SimplifyDemandedBits was "simplifying" a constant by removing just sign bits.
This caused a canonicalization race between different parts of instcombine.
Fix and regression test added - third time lucky?
llvm-svn: 237539
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The AArch64 LNT bot is unhappy - I've found that the problem is in
SimpliftDemandedBits, but that's going to require another code review
so reverting in the meantime.
llvm-svn: 237528
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... I'd copied the check-next lines from a previous test so they were
slightly wrong, and had managed to test the wrong source tree. D'oh!
llvm-svn: 237521
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The test timeouts were due to instcombine fighting itself. Regression test added.
Original log message:
Canonicalize min/max expressions correctly.
This patch introduces a canonical form for min/max idioms where one operand
is extended or truncated. This often happens when the other operand is a
constant. For example:
%1 = icmp slt i32 %a, i32 0
%2 = sext i32 %a to i64
%3 = select i1 %1, i64 %2, i64 0
Would now be canonicalized into:
%1 = icmp slt i32 %a, i32 0
%2 = select i1 %1, i32 %a, i32 0
%3 = sext i32 %2 to i64
This builds upon a patch posted by David Majenemer
(https://www.marc.info/?l=llvm-commits&m=143008038714141&w=2). That pass
passively stopped instcombine from ruining canonical patterns. This
patch additionally actively makes instcombine canonicalize too.
Canonicalization of expressions involving a change in type from int->fp
or fp->int are not yet implemented.
llvm-svn: 237520
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This reverts r237453 - it was causing timeouts on some bots. Reverting
while I investigate (it's probably InstCombine fighting itself...)
llvm-svn: 237458
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This patch introduces a canonical form for min/max idioms where one operand
is extended or truncated. This often happens when the other operand is a
constant. For example:
%1 = icmp slt i32 %a, i32 0
%2 = sext i32 %a to i64
%3 = select i1 %1, i64 %2, i64 0
Would now be canonicalized into:
%1 = icmp slt i32 %a, i32 0
%2 = select i1 %1, i32 %a, i32 0
%3 = sext i32 %2 to i64
This builds upon a patch posted by David Majenemer
(https://www.marc.info/?l=llvm-commits&m=143008038714141&w=2). That pass
passively stopped instcombine from ruining canonical patterns. This
patch additionally actively makes instcombine canonicalize too.
Canonicalization of expressions involving a change in type from int->fp
or fp->int are not yet implemented.
llvm-svn: 237453
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