Reapply [MergeICmps] Don't require GEP

Recommit without changes over 53abe3ff66a54117308352d379837c7d3229f8d6,
which addressed the cause of the reported crash.

-----

With opaque pointers, the zero

Reapply [MergeICmps] Don't require GEP

Recommit without changes over 53abe3ff66a54117308352d379837c7d3229f8d6,
which addressed the cause of the reported crash.

-----

With opaque pointers, the zero-offset load will generally not use
a GEP. Allow a direct load without GEP, which is treated the same
way as a zero-offset GEP.

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[MergeICmp] Make instruction move robust against empty block (NFCI)

Use the overload that support moving into an empty block. I don't
think that this situation can occur right now, but it can happen

[MergeICmp] Make instruction move robust against empty block (NFCI)

Use the overload that support moving into an empty block. I don't
think that this situation can occur right now, but it can happen
with the change from e7fb1c15cb85d748c1c4fdd5a2eb5613ec7bef1d,
and the test is derived from the issue reported there.

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Revert "[MergeICmps] Don't require GEP"

This reverts commit e7fb1c15cb85d748c1c4fdd5a2eb5613ec7bef1d.

Causes crashes, see https://reviews.llvm.org/rGe7fb1c15cb85d748c1c4fdd5a2eb5613ec7bef1d.

[MergeICmps] Don't require GEP

With opaque pointers, the zero-offset load will generally not use
a GEP. Allow a direct load without GEP, which is treated the same
way as a zero-offset GEP.

[MergeICmps] Don't call comesBefore() if in different blocks (PR53959)

Only call comesBefore() if the instructions are in the same block.
Otherwise make a conservative assumption.

Fixes https://git

[MergeICmps] Don't call comesBefore() if in different blocks (PR53959)

Only call comesBefore() if the instructions are in the same block.
Otherwise make a conservative assumption.

Fixes https://github.com/llvm/llvm-project/issues/53959.

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[MergeICmps] Remove unused NumMerged variable

[MergeICmps] Don't reorder unmerged comparisons

MergeICmps will currently sort (by offset) all comparisons in a chain,
including those that do not get merged. This is problematic in two ways:

* We

[MergeICmps] Don't reorder unmerged comparisons

MergeICmps will currently sort (by offset) all comparisons in a chain,
including those that do not get merged. This is problematic in two ways:

* We may end up moving the original first block into the middle of
the chain, in which case the "extra work" instructions will also
be in the middle of the chain, resulting in invalid IR
(reported in https://reviews.llvm.org/D108782#3005583).
* Reordering branches is generally not legal, because it may
introduce branch on poison, which is UB (PR51845). The merging
done by MergeICmps is legal as long as we assume that memcmp()
works on frozen memory, but the reordering of unmerged comparisons
is definitely incorrect (without inserting freeze instructions),
so we should avoid it.

There are easier ways to fix the first issue, but I figured it was
worthwhile to do this properly to also fix the second one. What we
now do is to restore the original relative order of (potentially
merged) comparisons.

I took the liberty of dropping the MERGEICMPS_DOT_ON functionality,
because it would be more awkward to implement now (as the before and
after representation is different) and it doesn't seem terribly
useful nowadays.

Differential Revision: https://reviews.llvm.org/D110024

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[llvm] Use drop_begin (NFC)

[MergeICmps] Ignore clobbering instructions before the loads

This is another followup to D106591. Even if there is an
instruction that clobbers one of the loads, this doesn't matter if
it happens be

[MergeICmps] Ignore clobbering instructions before the loads

This is another followup to D106591. Even if there is an
instruction that clobbers one of the loads, this doesn't matter if
it happens before the loads. Those instructions aren't affected by
the transform at all.

The gep-references-bb.ll is modified to preserve the spirit of the
test, as the store to @g no longer impacts the transform.

Differential Revision: https://reviews.llvm.org/D108782

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[MergeICmps] Don't merge icmps derived from pointers with addressspaces

IIUC we can't emit `memcmp` between pointers in addressspaces,
doing so will trigger an assertion since the signature of the m

[MergeICmps] Don't merge icmps derived from pointers with addressspaces

IIUC we can't emit `memcmp` between pointers in addressspaces,
doing so will trigger an assertion since the signature of the memcmp
will not match it's arguments (https://bugs.llvm.org/show_bug.cgi?id=48661).

This PR disables the attempt to merge icmps,
when the pointer is in an addressspace.

Reviewed By: #julialang, vtjnash

Differential Revision: https://reviews.llvm.org/D94813

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[MergeICmps] Allow sinking past non-load/store

This is a followup to D106591. MergeICmps currently only allows
sinking the loads past either instructions that don't write to
memory at all, or simple

[MergeICmps] Allow sinking past non-load/store

This is a followup to D106591. MergeICmps currently only allows
sinking the loads past either instructions that don't write to
memory at all, or simple loads/stores that don't modify the memory
the loads access.

The "simple loads/stores" part of this check doesn't seem necessary
to me -- AA isModRef() already accurately models any operation
that may clobber the memory. For example, in the adjusted test case
the transform is still fine if the call to @foo() isn't readonly,
but inaccessiblememonly -- in both cases, the call cannot modify
the loaded memory.

Differential Revision: https://reviews.llvm.org/D108517

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[MergeICmps] Collect block instructions once (NFC)

Collect the relevant instructions for a given BCECmpBlock once
on construction, rather than repeating this logic in multiple
places.

[MergeICmps] Try to fix MSVC build failure

Apparently this fails to line up the types -- try to sidestep the
issue entirely by writing the code in a more reasonable way: Walk
over the operands and p

[MergeICmps] Try to fix MSVC build failure

Apparently this fails to line up the types -- try to sidestep the
issue entirely by writing the code in a more reasonable way: Walk
over the operands and perform a set lookup, rather than walking
over the set and performing an operand scan.

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[MergeICmps] Separate out BCECmp and use Optional (NFC)

Separate out the BCECmp part from BCECmpBlock, which just stores
the comparison atoms without the branch instruction. At the same
time switch

[MergeICmps] Separate out BCECmp and use Optional (NFC)

Separate out the BCECmp part from BCECmpBlock, which just stores
the comparison atoms without the branch instruction. At the same
time switch the code to return Optional<> rather than objects in
invalid state and partially constructed objects.

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[MergeICmps] Relax sinking check

The check for sinking instructions past the load + cmp sequence
currently checks for side-effects, which includes writing to memory
and unwinding. However, I don't b

[MergeICmps] Relax sinking check

The check for sinking instructions past the load + cmp sequence
currently checks for side-effects, which includes writing to memory
and unwinding. However, I don't believe we care about sinking the
instructions past an unwind (as they don't have any side-effects
themselves).

Differential Revision: https://reviews.llvm.org/D106591

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PR51018: Remove explicit conversions from SmallString to StringRef to future-proof against C++23

C++23 will make these conversions ambiguous - so fix them to make the
codebase forward-compatible wit

PR51018: Remove explicit conversions from SmallString to StringRef to future-proof against C++23

C++23 will make these conversions ambiguous - so fix them to make the
codebase forward-compatible with C++23 (& a follow-up change I've made
will make this ambiguous/invalid even in <C++23 so we don't regress
this & it generally improves the code anyway)

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[NewPM] Don't mark AA analyses as preserved

Currently all AA analyses marked as preserved are stateless, not taking
into account their dependent analyses. So there's no need to mark them
as preserve

[NewPM] Don't mark AA analyses as preserved

Currently all AA analyses marked as preserved are stateless, not taking
into account their dependent analyses. So there's no need to mark them
as preserved, they won't be invalidated unless their analyses are.

SCEVAAResults was the one exception to this, it was treated like a
typical analysis result. Make it like the others and don't invalidate
unless SCEV is invalidated.

Reviewed By: asbirlea

Differential Revision: https://reviews.llvm.org/D102032

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[IR] Add BasicBlock::isEntryBlock() (NFC)

This is a recurring and somewhat awkward pattern. Add a helper
method for it.

[llvm][NFC] Fix assert indentation

This triggers GCC's misleading-indentation checker.

[Transforms/Scalar] Use range-based for loops (NFC)

[Transforms] Use llvm::find_if (NFC)

[MergeICmps] Fix missing split.

We were not correctly splitting a blocks for chains of length 1.

Before that change, additional instructions for blocks in chains of
length 1 were not split off from

[MergeICmps] Fix missing split.

We were not correctly splitting a blocks for chains of length 1.

Before that change, additional instructions for blocks in chains of
length 1 were not split off from the block before removing (this was
done correctly for chains of longer size).
If this first block contained an instruction referenced elsewhere,
deleting the block, would result in invalidation of the produced value.

This caused a miscompile which motivated D92297 (before D17993,
nonnull and dereferenceable attributed were not added so MergeICmps were
not triggered.) The new test gep-references-bb.ll demonstrate the issue.

The regression was introduced in
rG0efadbbcdeb82f5c14f38fbc2826107063ca48b2.

This supersedes D92364.

Test case by MaskRay (Fangrui Song).

Differential Revision: https://reviews.llvm.org/D92375

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[Transforms] visitCmpBlock - don't dereference a dyn_cast<>. NFCI.

Use cast<> as we immediately dereference the pointer afterwards - cast<> will assert if we fail.

Prevents clang static analyzer wa

[Transforms] visitCmpBlock - don't dereference a dyn_cast<>. NFCI.

Use cast<> as we immediately dereference the pointer afterwards - cast<> will assert if we fail.

Prevents clang static analyzer warning that we could deference a null pointer.

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Sink all InitializePasses.h includes

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 reco

Sink all InitializePasses.h includes

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

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Revert "Reland "r364412 [ExpandMemCmp][MergeICmps] Move passes out of CodeGen into opt pipeline.""

This reverts commit r371502, it broke tests
(clang/test/CodeGenCXX/auto-var-init.cpp).

llvm-svn: 3

Revert "Reland "r364412 [ExpandMemCmp][MergeICmps] Move passes out of CodeGen into opt pipeline.""

This reverts commit r371502, it broke tests
(clang/test/CodeGenCXX/auto-var-init.cpp).

llvm-svn: 371507

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