This reverts commit 13ccce28776d8ad27b0c6a92b5a452d62da05663.
The tests are on non-canonical IR, and adds an extra unrelated
pre-processing step to the pass. I'm assuming this is a workaround
for the known-bits recursion depth limit in instcombine.
Try to transform XOR(A, B+C) in to XOR(A,C) + B where XOR(A,C) becomes
the base for memory operations. This transformation is true under the
following conditions
Check 1 - B and C are disjoint.
Check 2 - XOR(A,C) and B are disjoint.
This transformation is beneficial particularly for GEPs because
Disjoint OR operations often map better to addressing modes than XOR.
This can enable further optimizations in the GEP offset folding pipeline
If we know that the initial GEP was inbounds, and we change it to a
sequence of GEPs from the same base pointer where every offset is
non-negative, then the new GEPs are inbounds.
We can also preserve inbounds if the inbounds GEP and the involved additions are NUW.
For SWDEV-516125.
The language reference says about inbounds geps that "if the
getelementptr has any non-zero indices[...] [t]he base pointer has an in
bounds address of the allocated object that it is based on [and]
[d]uring the successive addition of offsets to the address, the
resulting pointer must remain in bounds of the allocated object at each
step."
If (gep inbounds p, (a + 5)) is translated to (gep [inbounds] (gep p,
a), 5) with p pointing to the beginning of an object and a=-4, as the
example in the comments suggests, that's the case for neither of the
resulting geps. Therefore, we need to clear the inbounds flag for both
geps.
We might want to use ValueTracking to check if a is known to be
non-negative to preserve the inbounds flags.
For the AMDGPU tests with scratch instructions, removing the unsound
inbounds flag means that AMDGPUDAGToDAGISel::isFlatScratchBaseLegal sees
no NUW flag at the pointer add, which prevents generation of scratch
instructions with immediate offsets.
For SWDEV-516125.
As part of the "RemoveDIs" project, BasicBlock::iterator now carries a
debug-info bit that's needed when getFirstNonPHI and similar feed into
instruction insertion positions. Call-sites where that's necessary were
updated a year ago; but to ensure some type safety however, we'd like to
have all calls to moveBefore use iterators.
This patch adds a (guaranteed dereferenceable) iterator-taking
moveBefore, and changes a bunch of call-sites where it's obviously safe
to change to use it by just calling getIterator() on an instruction
pointer. A follow-up patch will contain less-obviously-safe changes.
We'll eventually deprecate and remove the instruction-pointer
insertBefore, but not before adding concise documentation of what
considerations are needed (very few).
This is a helper to avoid writing `getModule()->getDataLayout()`. I
regularly try to use this method only to remember it doesn't exist...
`getModule()->getDataLayout()` is also a common (the most common?)
reason why code has to include the Module.h header.
This implements the `nusw` and `nuw` flags for `getelementptr` as
proposed at
https://discourse.llvm.org/t/rfc-add-nusw-and-nuw-flags-for-getelementptr/78672.
The three possible flags are encapsulated in the new `GEPNoWrapFlags`
class. Currently this class has a ctor from bool, interpreted as the
InBounds flag. This ctor should be removed in the future, as code gets
migrated to handle all flags.
There are a few places annotated with `TODO(gep_nowrap)`, where I've had
to touch code but opted to not infer or precisely preserve the new
flags, so as to keep this as NFC as possible and make sure any changes
of that kind get test coverage when they are made.
The code was essentially already ready to handle multiple indices -- we
only need to adjust the non-negative index check to check all indices,
instead of only the first one.
As part of the RemoveDIs project we need LLVM to insert instructions using
iterators wherever possible, so that the iterators can carry a bit of
debug-info. This commit implements some of that by updating the contents of
llvm/lib/Transforms/Utils to always use iterator-versions of instruction
constructors.
There are two general flavours of update:
* Almost all call-sites just call getIterator on an instruction
* Several make use of an existing iterator (scenarios where the code is
actually significant for debug-info)
The underlying logic is that any call to getFirstInsertionPt or similar
APIs that identify the start of a block need to have that iterator passed
directly to the insertion function, without being converted to a bare
Instruction pointer along the way.
Noteworthy changes:
* FindInsertedValue now takes an optional iterator rather than an
instruction pointer, as we need to always insert with iterators,
* I've added a few iterator-taking versions of some value-tracking and
DomTree methods -- they just unwrap the iterator. These are purely
convenience methods to avoid extra syntax in some passes.
* A few calls to getNextNode become std::next instead (to keep in the
theme of using iterators for positions),
* SeparateConstOffsetFromGEP has it's insertion-position field changed.
Noteworthy because it's not a purely localised spelling change.
All this should be NFC.
"ninja check-llvm" is failing on tip of tree.
This reverts commit ec0aa1646e9953d1a8d0d15dc381d3250c854572.
This reverts commit 1b65742f8c71f576381fe85d5e34579b24f2d874.
In this case, a trivial GEP chain has the form:
```
%ptr = getelementptr sameType, %base, constant
%val = getelementptr sameType, %ptr, %variable
```
That is, a one-index GEP consumes another (of the same basis and result
type) one-index GEP, where the inner GEP uses a constant index and the
outer GEP uses a variable index. For chains of this type, it is trivial
to reorder them (by simply swapping the indexes). The result of doing so
is better AddrMode matching for users of the ultimate ptr produced by
GEP chain.
Future patches can extend this to support non-trivial GEP chains (e.g.
those with different basis types and/or multiple indices).
This commit extends separate-const-offset-from-gep to look at the
newly-added `disjoint` flag on `or` instructions so as to preserve
additional opportunities for optimization.
The tests were pre-committed in #76972.
Vectors are always bit-packed and don't respect the elements' alignment
requirements. This is different from arrays. This means offsets of
vector GEPs need to be computed differently than offsets of array GEPs.
This PR fixes many places that rely on an incorrect pattern
that always relies on `DL.getTypeAllocSize(GTI.getIndexedType())`.
We replace these by usages of `GTI.getSequentialElementStride(DL)`,
which is a new helper function added in this PR.
This changes behavior for GEPs into vectors with element types for which
the (bit) size and alloc size is different. This includes two cases:
* Types with a bit size that is not a multiple of a byte, e.g. i1.
GEPs into such vectors are questionable to begin with, as some elements
are not even addressable.
* Overaligned types, e.g. i16 with 32-bit alignment.
Existing tests are unaffected, but a miscompilation of a new test is fixed.
---------
Co-authored-by: Nikita Popov <github@npopov.com>
Fix bug constants and sub instructions
When finding constants in a chain starting with the RHS operator of
sub instructions, we were negating the constant before zero extending
it, which is incorrect.
Unfortunately, I was unable to find a simple way to implement this
transformation correctly, so for now I just disabled this optimization
for constants that feed into the RHS of a sub.
Resolves#62379
Transformation from alive2.llvm.org:
define i16 @src(i8 %a, i8 %b, i8 %c) {
entry:
%0 = sub nuw nsw i8 %c, %a
%1 = sub nuw nsw i8 %b, %0
%2 = zext i8 %1 to i16
ret i16 %2
}
Before/Bad:
define i16 @tgt(i8 %a, i8 %b, i8 %c) {
entry:
%0 = zext i8 %a to i16
%1 = zext i8 %b to i16
%c_neg = sub i8 0, %c
%c_zext = zext i8 %c_neg to i16
%2 = sub i16 0, %0
%3 = sub i16 %1, %2
%4 = add i16 %3, %c_zext
ret i16 %4
}
Correct:
define i16 @tgt(i8 %a, i8 %b, i8 %c) {
entry:
%0 = zext i8 %a to i16
%1 = zext i8 %b to i16
%c_zext = zext i8 %c to i16
%c_neg = sub i16 0, %c_zext
%2 = sub i16 0, %0
%3 = sub i16 %1, %2
%4 = add i16 %3, %c_neg
ret i16 %4
}
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D149507
Many uses of getIntPtrType() were using that type to calculate the
neened type for GEP offset arguments. However, some time ago,
DataLayout was extended to support pointers where the size of the
pointer is not equal to the size of the values used to index it.
Much code was already migrated to, for example, use getIndexSizeInBits
instead of getPtrSizeInBits, but some rewrites still used
getIntPtrType() to get the type for GEP offsets.
This commit changes uses of getIntPtrType() to getIndexType() where
they are involved in a GEP-related calculation.
In at least one case (bounds check insertion) this resolves a compiler
crash that the new test added here would previously trigger.
This commit does not impact
- C library-related rewriting (memcpy()), which are operating under
the assumption that intptr_t == size_t. While all the mechanisms for
breaking this assumption now exist, doing so is outside the scope of
this commit.
- Code generation and below. Note that the use of getIntPtrType() in
CodeGenPrepare will be changed in a future commit.
- Usage of getIntPtrType() in any backend
Depends on D143435
Reviewed By: arichardson
Differential Revision: https://reviews.llvm.org/D143437
We need such a flag to check whether the transformation is correct if
LowerGEP was enabled.
Reviewed By: nikic, arsenm, spatel
Differential Revision: https://reviews.llvm.org/D143980
ResultPtr is guaranteed to be non-null - and using dyn_cast_or_null causes unnecessary static analyzer warnings.
We can't say the same for FirstResult AFAICT, so keep dyn_cast_or_null for that.
Summary:
This is RFC for fixes in poison-related functions of ValueTracking.
These functions assume that a value can be poison bitwisely, but the semantics
of bitwise poison is not clear at the moment.
Allowing a value to have bitwise poison adds complexity to reasoning about
correctness of optimizations.
This patch makes the analysis functions simply assume that a value is
either fully poison or not, which has been used to understand the correctness
of a few previous optimizations.
The bitwise poison semantics seems to be only used by these functions as well.
In terms of implementation, using value-wise poison concept makes existing
functions do more precise analysis, which is what this patch contains.
Reviewers: spatel, lebedev.ri, jdoerfert, reames, nikic, nlopes, regehr
Reviewed By: nikic
Subscribers: fhahn, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78503
Summary:
This is RFC for fixes in poison-related functions of ValueTracking.
These functions assume that a value can be poison bitwisely, but the semantics
of bitwise poison is not clear at the moment.
Allowing a value to have bitwise poison adds complexity to reasoning about
correctness of optimizations.
This patch makes the analysis functions simply assume that a value is
either fully poison or not, which has been used to understand the correctness
of a few previous optimizations.
The bitwise poison semantics seems to be only used by these functions as well.
In terms of implementation, using value-wise poison concept makes existing
functions do more precise analysis, which is what this patch contains.
Reviewers: spatel, lebedev.ri, jdoerfert, reames, nikic, nlopes, regehr
Reviewed By: nikic
Subscribers: fhahn, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78503
find() was altering the UserChain, even in cases where it subsequently
discovered that the resulting constant was a 0. This confuses
rebuildWithoutConstOffset() when it attempts to walk the chain later, since it
is expected that the chain itself be a path down the use-def edges of an
expression.
During the SeparateConstOffsetFromGEP pass, signed extensions are distributed
to the values that feed into them and then later recombined. The recombination
stage is somewhat problematic- it doesn't differ add and sub instructions
from another when matching the sext(a) +/- sext(b) -> sext(a +/- b) pattern
in some instances.
An example- the IR contains:
%unextendedA
%unextendedB
%subuAuB = unextendedA - unextendedB
%extA = extend A
%extB = extend B
%addeAeB = extA + extB
The problematic optimization will transform that into:
%unextendedA
%unextendedB
%subuAuB = unextendedA - unextendedB
%extA = extend A
%extB = extend B
%addeAeB = extend subuAuB ; Obviously not semantically equivalent to the IR input.
This patch fixes that.
Patch by Drew Wock <drew.wock@sas.com>
Differential Revision: https://reviews.llvm.org/D65967
This file lists every pass in LLVM, and is included by Pass.h, which is
very popular. Every time we add, remove, or rename a pass in LLVM, it
caused lots of recompilation.
I found this fact by looking at this table, which is sorted by the
number of times a file was changed over the last 100,000 git commits
multiplied by the number of object files that depend on it in the
current checkout:
recompiles touches affected_files header
342380 95 3604 llvm/include/llvm/ADT/STLExtras.h
314730 234 1345 llvm/include/llvm/InitializePasses.h
307036 118 2602 llvm/include/llvm/ADT/APInt.h
213049 59 3611 llvm/include/llvm/Support/MathExtras.h
170422 47 3626 llvm/include/llvm/Support/Compiler.h
162225 45 3605 llvm/include/llvm/ADT/Optional.h
158319 63 2513 llvm/include/llvm/ADT/Triple.h
140322 39 3598 llvm/include/llvm/ADT/StringRef.h
137647 59 2333 llvm/include/llvm/Support/Error.h
131619 73 1803 llvm/include/llvm/Support/FileSystem.h
Before this change, touching InitializePasses.h would cause 1345 files
to recompile. After this change, touching it only causes 550 compiles in
an incremental rebuild.
Reviewers: bkramer, asbirlea, bollu, jdoerfert
Differential Revision: https://reviews.llvm.org/D70211
Summary:
This is the first change to enable the TLI to be built per-function so
that -fno-builtin* handling can be migrated to use function attributes.
See discussion on D61634 for background. This is an enabler for fixing
handling of these options for LTO, for example.
This change should not affect behavior, as the provided function is not
yet used to build a specifically per-function TLI, but rather enables
that migration.
Most of the changes were very mechanical, e.g. passing a Function to the
legacy analysis pass's getTLI interface, or in Module level cases,
adding a callback. This is similar to the way the per-function TTI
analysis works.
There was one place where we were looking for builtins but not in the
context of a specific function. See FindCXAAtExit in
lib/Transforms/IPO/GlobalOpt.cpp. I'm somewhat concerned my workaround
could provide the wrong behavior in some corner cases. Suggestions
welcome.
Reviewers: chandlerc, hfinkel
Subscribers: arsenm, dschuff, jvesely, nhaehnle, mehdi_amini, javed.absar, sbc100, jgravelle-google, eraman, aheejin, steven_wu, george.burgess.iv, dexonsmith, jfb, asbirlea, gchatelet, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D66428
llvm-svn: 371284
