As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
Summary: This restores the combine that was reverted in r341883. The infinite loop from the failing test no longer occurs due to changes from r342163.
Reviewers: spatel, dmgreen
Reviewed By: spatel
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D52070
llvm-svn: 342797
Summary:
Revert min/max changes in rL341674 dues to high compile times causing timeouts (PR38897).
Checking in to unblock failing builds. Patch available for post-commit review and re-revert once resolved.
Working on a smaller reproducer for PR38897.
Reviewers: craig.topper, spatel
Subscribers: sanjoy, jlebar, llvm-commits
Differential Revision: https://reviews.llvm.org/D51897
llvm-svn: 341883
If the ~X wasn't able to simplify above the max/min, we might be able to simplify it by moving it below the max/min.
I had to modify the ~(min/max ~X, Y) transform to prevent getting stuck in a loop when we saw the new ~(max/min X, ~Y) before the ~Y had been folded away to remove the new not.
Differential Revision: https://reviews.llvm.org/D51398
llvm-svn: 341674
We already do this for min/max (see the blob above the diff),
so we should do the same for abs/nabs.
A sign-bit check (<s 0) is used as a predicate for other IR
transforms and it's likely the best for codegen.
This might solve the motivating cases for D47037 and D47041,
but I think those patches still make sense. We can't guarantee
this canonicalization if the icmp has more than one use.
Differential Revision: https://reviews.llvm.org/D47076
llvm-svn: 332819
These are based on:
https://bugs.llvm.org/show_bug.cgi?id=35875
It's not clear if/how instcombine can reduce these,
but we should have the tests here either way to
document current behavior.
llvm-svn: 327039
This was originally planned as the fix for:
https://bugs.llvm.org/show_bug.cgi?id=35834
...but simpler transforms handled that case, so I implemented a
lesser solution. It turns out we need to handle the case with 'not'
ops too because the real code example that we are trying to solve:
https://bugs.llvm.org/show_bug.cgi?id=35875
...has extra uses of the intermediate values, so we can't rely on
smaller canonicalizations to get us to the goal.
As with rL321672, I've tried to show every possibility in the
codegen tests because that's the simplest way to prove we're doing
the right thing in the wide variety of permutations of this pattern.
We can also show an InstCombine win because we added a fold for
this case in:
rL321998 / D41603
An Alive proof for one variant of the pattern to show that the
InstCombine and codegen results are correct:
https://rise4fun.com/Alive/vd1
Name: min3_nots
%nx = xor i8 %x, -1
%ny = xor i8 %y, -1
%nz = xor i8 %z, -1
%cmpxz = icmp slt i8 %nx, %nz
%minxz = select i1 %cmpxz, i8 %nx, i8 %nz
%cmpyz = icmp slt i8 %ny, %nz
%minyz = select i1 %cmpyz, i8 %ny, i8 %nz
%cmpyx = icmp slt i8 %y, %x
%r = select i1 %cmpyx, i8 %minxz, i8 %minyz
=>
%cmpxyz = icmp slt i8 %minxz, %ny
%r = select i1 %cmpxyz, i8 %minxz, i8 %ny
Name: min3_nots_alt
%nx = xor i8 %x, -1
%ny = xor i8 %y, -1
%nz = xor i8 %z, -1
%cmpxz = icmp slt i8 %nx, %nz
%minxz = select i1 %cmpxz, i8 %nx, i8 %nz
%cmpyz = icmp slt i8 %ny, %nz
%minyz = select i1 %cmpyz, i8 %ny, i8 %nz
%cmpyx = icmp slt i8 %y, %x
%r = select i1 %cmpyx, i8 %minxz, i8 %minyz
=>
%xz = icmp sgt i8 %x, %z
%maxxz = select i1 %xz, i8 %x, i8 %z
%xyz = icmp sgt i8 %maxxz, %y
%maxxyz = select i1 %xyz, i8 %maxxz, i8 %y
%r = xor i8 %maxxyz, -1
llvm-svn: 322283
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/Qjnehttps://rise4fun.com/Alive/3yg
Differential Revision: https://reviews.llvm.org/D41603
llvm-svn: 321998
In the minimal case, this won't remove instructions, but it still improves
uses of existing values.
In the motivating example from PR35834, it does remove instructions, and
sets that case up to be optimized by something like D41603:
https://reviews.llvm.org/D41603
llvm-svn: 321936
Besides the bug of omitting the inverse transform of max(~a, ~b) --> ~min(a, b),
the use checking and operand creation were off. We were potentially creating
repeated identical instructions of existing values. This led to infinite
looping after I added the extra folds.
By using the simpler m_Not matcher and not creating new 'not' ops for a and b,
we avoid that problem. It's possible that not using IsFreeToInvert() here is
more limiting than the simpler matcher, but there are no tests for anything
more exotic. It's also possible that we should relax the use checking further
to handle a case like PR35834:
https://bugs.llvm.org/show_bug.cgi?id=35834
...but we can make that a follow-up if it is needed.
llvm-svn: 321882
This canonicalization was suggested in D33172 as a way to make InstCombine behavior more uniform.
We have this transform for icmp+br, so unless there's some reason that icmp+select should be
treated differently, we should do the same thing here.
The benefit comes from increasing the chances of creating identical instructions. This is shown in
the tests in logical-select.ll (PR32791). InstCombine doesn't fold those directly, but EarlyCSE
can simplify the identical cmps, and then InstCombine can fold the selects together.
The possible regression for the tests in select.ll raises questions about poison/undef:
http://lists.llvm.org/pipermail/llvm-dev/2017-May/113261.html
...but that transform is just as likely to be triggered by this canonicalization as it is to be
missed, so we're just pointing out a commutation deficiency in the pattern matching:
https://reviews.llvm.org/rL228409
Differential Revision: https://reviews.llvm.org/D34242
llvm-svn: 306435
Summary:
This is a fix for assertion failure in
`getInverseMinMaxSelectPattern` when ABS is passed in as a select pattern.
We should not be invoking the simplification rule for
ABS(MIN(~ x,y))) or ABS(MAX(~x,y)) combinations.
Added a test case which would cause an assertion failure without the patch.
Reviewers: sanjoy, majnemer
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D30051
llvm-svn: 295719
As the test change shows, we can increase the critical path by adding
a 'not' instruction, so make sure that we're actually removing an
instruction if we do this transform.
This transform could also cause us to miss folds of min/max pairs.
llvm-svn: 286315
Try harder to detect obfuscated min/max patterns: the initial pattern was added with D9352 / rL236202.
There was a bug fix for PR27137 at rL264996, but I think we can do better by folding the corresponding
smax pattern and commuted variants.
The codegen tests demonstrate the effect of ValueTracking on the backend via SelectionDAGBuilder. We
can't expose these differences minimally in IR because we don't have smin/smax intrinsics for IR.
Differential Revision: https://reviews.llvm.org/D26091
llvm-svn: 285499
Summary:
Optimizing these well are especially interesting for IRCE since it
"clamps" values by generating this sort of pattern through SCEV
expressions.
Depends on D9352.
Reviewers: majnemer
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D9353
llvm-svn: 236203
This case is interesting because ScalarEvolutionExpander lowers min(a,
b) as ~max(~a,~b). I think the profitability heuristics can be made
more clever/aggressive, but this is a start.
Differential Revision: http://reviews.llvm.org/D7821
llvm-svn: 230285
Eric Christopher