Summary:
```
br i1 c, BB1, BB2:
BB1:
use1(c)
BB2:
use2(c)
```
In BB1 and BB2, c is never undef or poison because otherwise the branch would have triggered UB.
Checked with Alive2
Reviewers: xbolva00, spatel, lebedev.ri, reames, jdoerfert, nlopes, sanjoy
Reviewed By: reames
Subscribers: jdoerfert, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D75401
Summary:
This patch helps getGuaranteedNonFullPoisonOp handle llvm.assume call.
Also, a comment about the semantics of branch is removed to prevent confusion.
As llvm.assume does, branching on poison directly raises UB (as LangRef says), and this allows transformations such as introduction of llvm.assume on branch condition at each successor, or freely replacing values after conditional branch (such as at loop exit).
Handling br is not addressed in this patch. It makes SCEV more accurate, causing existing LoopVectorize/IndVar/etc tests to fail.
Reviewers: spatel, lebedev.ri, nlopes
Reviewed By: nlopes
Subscribers: hiraditya, javed.absar, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D75397
Summary:
This patch helps isGuaranteedNotToBeUndefOrPoison return true if the value
makes the program always undefined.
According to value tracking functions' comments, it is not still in consensus
whether a poison value can be bitwise or not, so conservatively only the case with
i1 is considered.
Reviewers: spatel, lebedev.ri, reames, nlopes, regehr
Reviewed By: nlopes
Subscribers: uenoku, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D75396
isKnownNonNaN() could not recognize a zero splat because that is a
ConstantAggregateZero which is-a ConstantData but not a ConstantDataVector.
Patch makes a ConstantAggregateZero return true.
Review: Thomas Lively
Differential Revision: https://reviews.llvm.org/D74263
Summary:
This was a very odd API, where you had to pass a flag into a zext
function to say whether the extended bits really were zero or not. All
callers passed in a literal true or false.
I think it's much clearer to make the function name reflect the
operation being performed on the value we're tracking (rather than on
the KnownBits Zero and One fields), so zext means the value is being
zero extended and new function anyext means the value is being extended
with unknown bits.
NFC.
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D74482
If we know that a >= b (unsigned), usub.with.overflow(a, b) cannot
overflow. Similarly, if b > a, the same expression overflows.
Reviewers: nikic, RKSimon, lebedev.ri, spatel
Reviewed By: nikic, Gerolf
Differential Revision: https://reviews.llvm.org/D74066
This patch adds versions of isImpliedCondition and
isImpliedByDomCondition that take a predicate, LHS and RHS operands as
instead of a Value representing the condition.
This allows using those functions to check conditions without having a
concrete ICmp instruction.
Reviewers: nikic, RKSimon, lebedev.ri, spatel
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D74065
This patch adds initial support for a DemandedElts mask to the internal computeKnownBits/ComputeNumSignBits methods, matching the SelectionDAG and GlobalISel equivalents.
So far only a couple of instructions have been setup to handle the DemandedElts, the remainder still using the existing 'all elements' default. The plan is to extend support as we have test coverage.
Differential Revision: https://reviews.llvm.org/D73435
This addresses https://bugs.llvm.org/show_bug.cgi?id=42801.
The m_c_ICmp() matcher is changed to provide the swapped predicate
if the operands are swapped.
Existing uses of m_c_ICmp() fall in one of two categories: Working
on equality predicates only, where swapping is irrelevant.
Or performing a manual swap, in which case this patch removes it.
The only exception is the foldICmpWithLowBitMaskedVal() fold, which
does not swap the predicate, and instead reasons about whether
a swap occurred or not for each predicate. Getting the swapped
predicate allows us to merge the logic for pairs of predicates,
instead of duplicating it.
Differential Revision: https://reviews.llvm.org/D72976
Summary:
It is pretty common to assume that something is not zero.
Even optimizer itself sometimes emits such assumptions
(e.g. `addAssumeNonNull()` in `PromoteMemoryToRegister.cpp`).
But we currently don't deal with such assumptions :)
The only way `isKnownNonZero()` handles assumptions is
by calling `computeKnownBits()` which calls `computeKnownBitsFromAssume()`.
But `x != 0` does not tell us anything about set bits,
it only says that there are *some* set bits.
So naturally, `KnownBits` does not get populated,
and we fail to make use of this assumption.
I propose to deal with this special case by special-casing it
via adding a `isKnownNonZeroFromAssume()` that returns boolean
when there is an applicable assumption.
While there, we also deal with other predicates,
mainly if the comparison is with constant.
Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=43267 | PR43267 ]].
Differential Revision: https://reviews.llvm.org/D71660
This is a pretty rare case, when CxtI and assume are
in the same basic block, with assume being located later.
We were already checking that assumption was guaranteed to be
executed, but we omitted CxtI itself from consideration,
and as the test (miscompile) shows, that is incorrect.
As noted in D71660 review by @nikic.
GEP index size can be specified in the DataLayout, introduced in D42123. However, there were still places
in which getIndexSizeInBits was used interchangeably with getPointerSizeInBits. This notably caused issues
with Instcombine's visitPtrToInt; but the unit tests was incorrect, so this remained undiscovered.
This fixes the buildbot failures.
Differential Revision: https://reviews.llvm.org/D68328
Patch by Joseph Faulls!
GEP index size can be specified in the DataLayout, introduced in D42123. However, there were still places
in which getIndexSizeInBits was used interchangeably with getPointerSizeInBits. This notably caused issues
with Instcombine's visitPtrToInt; but the unit tests was incorrect, so this remained undiscovered.
Differential Revision: https://reviews.llvm.org/D68328
Patch by Joseph Faulls!
This has two main effects:
- Optimizes debug info size by saving 221.86 MB of obj file size in a
Windows optimized+debug build of 'all'. This is 3.03% of 7,332.7MB of
object file size.
- Incremental step towards decoupling target intrinsics.
The enums are still compact, so adding and removing a single
target-specific intrinsic will trigger a rebuild of all of LLVM.
Assigning distinct target id spaces is potential future work.
Part of PR34259
Reviewers: efriedma, echristo, MaskRay
Reviewed By: echristo, MaskRay
Differential Revision: https://reviews.llvm.org/D71320
If the pointer was loaded/stored before the null check, the check
is redundant and can be removed. For now the optimizers do not
remove the nullptr check, see https://gcc.godbolt.org/z/H2r5GG.
The patch allows to use more nonnull constraints. Also, it found
one more optimization in some PowerPC test. This is my first llvm
review, I am free to any comments.
Differential Revision: https://reviews.llvm.org/D71177
Summary:
Same as D60846 and D69571 but with a fix for the problem encountered
after them. Both times it was a missing context adjustment in the
handling of PHI nodes.
The reproducers created from the bugs that caused the old commits to be
reverted are included.
Reviewers: nikic, nlopes, mkazantsev, spatel, dlrobertson, uabelho, hakzsam, hans
Subscribers: hiraditya, bollu, asbirlea, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D71181
As it can be seen from accompanying cleanup, it is not unheard of
to write `~Known.Zero` meaning "what maximal value can this KnownBits
produce". But i think `~Known.Zero` isn't *that* self-explanatory,
as compared to a method with a name.
Note that not all `~Known.Zero` places were cleaned up,
only those where this arguably improves things.
This caused miscompiles of Chromium (https://crbug.com/1023818). The reduced
repro is small enough to fit here:
$ cat /tmp/a.c
unsigned char f(unsigned char *p) {
unsigned char result = 0;
for (int shift = 0; shift < 1; ++shift)
result |= p[0] << (shift * 8);
return result;
}
$ bin/clang -O2 -S -o - /tmp/a.c | grep -A4 f:
f: # @f
.cfi_startproc
# %bb.0: # %entry
xorl %eax, %eax
retq
That's nicely optimized, but I don't think it's the right result :-)
> Same as D60846 but with a fix for the problem encountered there which
> was a missing context adjustment in the handling of PHI nodes.
>
> The test that caused D60846 to be reverted was added in e15ab8f277c7.
>
> Reviewers: nikic, nlopes, mkazantsev,spatel, dlrobertson, uabelho, hakzsam
>
> Subscribers: hiraditya, bollu, llvm-commits
>
> Tags: #llvm
>
> Differential Revision: https://reviews.llvm.org/D69571
This reverts commit 57dd4b03e4806bbb4760ab6150940150d884df20.
Same as D60846 but with a fix for the problem encountered there which
was a missing context adjustment in the handling of PHI nodes.
The test that caused D60846 to be reverted was added in e15ab8f277c7.
Reviewers: nikic, nlopes, mkazantsev,spatel, dlrobertson, uabelho, hakzsam
Subscribers: hiraditya, bollu, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D69571
This patch improves the handling of pointer offset in GEP expressions where
one argument is the base pointer. isPointerOffset() is being used by memcpyopt
where current code synthesizes consecutive 32 bytes stores to one store and
two memset intrinsic calls. With this patch, we convert the stores to one
memset intrinsic.
Differential Revision: https://reviews.llvm.org/D67989
llvm-svn: 374454
The static analyzer is warning about a potential null dereferences, but since the pointer is only used in a switch statement for Operator::getOpcode() (with an empty default) then its easiest just to wrap this in a null test as the dyn_cast might return null here.
llvm-svn: 372962
Static analyzer complains about const_cast uninitialized variables, we should explicitly set these to null.
Ideally that const wrapper would go away though.......
llvm-svn: 372603
Expose a utility function so that all places which want to suppress speculation (when otherwise legal) due to ordering and/or sanitizer interaction can do so.
llvm-svn: 371556
Summary:
Simplify the API using Optional<> and address comments in
https://reviews.llvm.org/D66165
Reviewers: vitalybuka
Subscribers: hiraditya, llvm-commits, ostannard, pcc
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D66317
llvm-svn: 369300
Summary:
Currently we fail to compute known bits for recurrences where the
first incoming value is the start value of the recurrence.
Instead of exiting the loop when the first incoming value is not
the step of the recurrence, continue to check the second incoming
value.
The original code uses a loop to handle both cases, but incorrectly
exits instead of continuing.
Reviewers: lebedev.ri, spatel, nikic
Reviewed By: lebedev.ri
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D66216
llvm-svn: 369088
Some uses of getArgumentAliasingToReturnedPointer and
isIntrinsicReturningPointerAliasingArgumentWithoutCapturing require the
calls/intrinsics to preserve the nullness of the argument.
For alias analysis, the nullness property does not really come into
play.
This patch explicitly sets it to true. In D61669, the alias analysis
uses will be switched to not require preserving nullness.
Reviewers: nlopes, efriedma, hfinkel, sanjoy, aqjune, jdoerfert
Reviewed By: jdoerfert
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D64150
llvm-svn: 368993
Use isGuaranteedToTransferExecutionToSuccessor() instead of
isSafeToSpeculativelyExecute() when seeing whether we can propagate
the information in an assume backwards in isValidAssumeForContext().
The latter is more general - it also allows arbitrary loads/stores -
and is also the condition we want: if our assume is guaranteed to
execute, its condition not holding would be UB.
Original patch by arielb1.
Differential Revision: https://reviews.llvm.org/D37215
llvm-svn: 368723
The matchSelectPattern code can match patterns like (x >= 0) ? x : -x
for absolute value. But it can also match ((x-y) >= 0) ? (x-y) : (y-x).
If the latter form was matched we can only use the nsw flag if its
set on both subtracts.
This match makes sure we're looking at the former case only.
Differential Revision: https://reviews.llvm.org/D65692
llvm-svn: 368195
Summary:
In D37215, AssumeLikeInstruction are regarded as `willreturn`. In this patch, annotation is added to those which don't have `willreturn` now(`sideeffect, object_size, experimental_widenable_condition`).
Reviewers: jdoerfert, nikic, sstefan1
Reviewed By: nikic
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D65455
llvm-svn: 367342
Summary: As clarified in D53184, volatile load and store do not trap. Therefore, we should remove volatile checks for instructions in `isGuaranteedToTransferExecutionToSuccessor`.
Reviewers: jdoerfert, efriedma, nikic
Reviewed By: nikic
Subscribers: hiraditya, jfb, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D65375
llvm-svn: 367226
Implement IR intrinsics for stack tagging. Generated code is very
unoptimized for now.
Two special intrinsics, llvm.aarch64.irg.sp and llvm.aarch64.tagp are
used to implement a tagged stack frame pointer in a virtual register.
Differential Revision: https://reviews.llvm.org/D64172
llvm-svn: 366360
Summary: Vector of the same value with few undefs will sill be considered "Bytewise"
Reviewers: eugenis, pcc, jfb
Reviewed By: jfb
Subscribers: dexonsmith, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D64031
llvm-svn: 365971
Summary:
This helps with more efficient use of memset for pattern initialization
From @pcc prototype for -ftrivial-auto-var-init=pattern optimizations
Binary size change on CTMark, (with -fuse-ld=lld -Wl,--icf=all, similar results with default linker options)
```
master patch diff
Os 8.238864e+05 8.238864e+05 0.0
O3 1.054797e+06 1.054797e+06 0.0
Os zero 8.292384e+05 8.292384e+05 0.0
O3 zero 1.062626e+06 1.062626e+06 0.0
Os pattern 8.579712e+05 8.338048e+05 -0.030299
O3 pattern 1.090502e+06 1.067574e+06 -0.020481
```
Zero vs Pattern on master
```
zero pattern diff
Os 8.292384e+05 8.579712e+05 0.036578
O3 1.062626e+06 1.090502e+06 0.025124
```
Zero vs Pattern with the patch
```
zero pattern diff
Os 8.292384e+05 8.338048e+05 0.003333
O3 1.062626e+06 1.067574e+06 0.003193
```
Reviewers: pcc, eugenis
Subscribers: hiraditya, cfe-commits, llvm-commits
Tags: #clang, #llvm
Differential Revision: https://reviews.llvm.org/D63967
llvm-svn: 365858
This patch replaces the three almost identical "strip & accumulate"
implementations for constant pointer offsets with a single one,
combining the respective functionalities. The old interfaces are kept
for now.
Differential Revision: https://reviews.llvm.org/D64468
llvm-svn: 365723
Summary:
We will need to handle IntToPtr which I will submit in a separate patch as it's
not going to be NFC.
Reviewers: eugenis, pcc
Reviewed By: eugenis
Subscribers: hiraditya, cfe-commits, llvm-commits
Tags: #clang, #llvm
Differential Revision: https://reviews.llvm.org/D63940
llvm-svn: 365709
