[IR] Convert from nocapture to captures(none) (#123181)

This PR removes the old `nocapture` attribute, replacing it with the new
`captures` attribute introduced in #116990. This change is
intended

[IR] Convert from nocapture to captures(none) (#123181)

This PR removes the old `nocapture` attribute, replacing it with the new
`captures` attribute introduced in #116990. This change is
intended to be essentially NFC, replacing existing uses of `nocapture`
with `captures(none)` without adding any new analysis capabilities.
Making use of non-`none` values is left for a followup.

Some notes:
* `nocapture` will be upgraded to `captures(none)` by the bitcode
reader.
* `nocapture` will also be upgraded by the textual IR reader. This is to
make it easier to use old IR files and somewhat reduce the test churn in
this PR.
* Helper APIs like `doesNotCapture()` will check for `captures(none)`.
* MLIR import will convert `captures(none)` into an `llvm.nocapture`
attribute. The representation in the LLVM IR dialect should be updated
separately.

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[FunctionAttrs] Unconditionally perform argument attribute inference in the first function-attrs pass

Summary:
Argument attributes like NoAlias and ReadOnly could affect memoryssa and thus earlyCS

[FunctionAttrs] Unconditionally perform argument attribute inference in the first function-attrs pass

Summary:
Argument attributes like NoAlias and ReadOnly could affect memoryssa and thus earlyCSE in the function simplification pipeline.
https://reviews.llvm.org/D145210 adjusted PostOrderFunctionAttrs placement and caused the argument attributes not referred for the use
in the pipeline. This work (initiated by @nikic) unconditionally performs argument attribute inference in the first function-attrs pass.

Reviewers:
aeubanks and nikic

Differential Revision:
https://reviews.llvm.org/D156397

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[Pipeline] Adjust PostOrderFunctionAttrs placement in simplification pipeline

We can infer more attribute information once functions are fully
simplified, so move the PostOrderFunctionAttrs pass aft

[Pipeline] Adjust PostOrderFunctionAttrs placement in simplification pipeline

We can infer more attribute information once functions are fully
simplified, so move the PostOrderFunctionAttrs pass after the function
simplification pipeline. However, just doing this can impact
simplification of recursive functions since function simplification
takes advantage of function attributes of callees (some LLVM tests are
actually impacted by this), so keep a copy of PostOrderFunctionAttrs
before the function simplification pipeline that only runs on recursive
functions.

For example, this fixes the small regression noticed in https://reviews.llvm.org/D128830.

This requires some restructuring of the CGSCC NoRerun feature. We need
to cache the ShouldNotRunFunctionPassesAnalysis analysis after the
simplification is done, which now is after the second
PostOrderFunctionAttrs run, rather than after the function
simplification pipeline.

Compile time impact:
https://llvm-compile-time-tracker.com/compare.php?from=33cf40122279342b50f92a3a53f5c185390b6018&to=1bb2a07875634e508a6bdf2ca1b130f55510f060&stat=instructions:u

Compile time increase from unconditionally running the first PostOrderFunctionAttrs:
https://llvm-compile-time-tracker.com/compare.php?from=1bb2a07875634e508a6bdf2ca1b130f55510f060&to=f4f87e89cc7a35c64e3a103a8036192a84ae002b&stat=instructions:u

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D145210

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Revert "Reland "[SimplifyCFG] `FoldBranchToCommonDest()`: deal with mismatched IV's in PHI's in common successor block""

One of these two changes is exposing (or causing) some more miscompiles.
A re

Revert "Reland "[SimplifyCFG] `FoldBranchToCommonDest()`: deal with mismatched IV's in PHI's in common successor block""

One of these two changes is exposing (or causing) some more miscompiles.
A reproducer is in progress, so reverting until resolved.

This reverts commit 428f36401b1b695fd501ebfdc8773bed8ced8d4e.

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Reland "[SimplifyCFG] `FoldBranchToCommonDest()`: deal with mismatched IV's in PHI's in common successor block"

This reverts commit 37b8f09a4b61bf9bf9d0b9017d790c8b82be2e17,
and returns commit 1bd0b

Reland "[SimplifyCFG] `FoldBranchToCommonDest()`: deal with mismatched IV's in PHI's in common successor block"

This reverts commit 37b8f09a4b61bf9bf9d0b9017d790c8b82be2e17,
and returns commit 1bd0b82e508d049efdb07f4f8a342f35818df341.
The miscompile was in InstCombine, and it has been addressed.

This tries to approach the problem noted by @arsenm:
terrible codegen for `__builtin_fpclassify()`:
https://godbolt.org/z/388zqdE37

Just because the PHI in the common successor happens to have different
incoming values for these two blocks, doesn't mean we have to give up.
It's quite easy to deal with this, we just need to produce a select:
https://alive2.llvm.org/ce/z/000srb

Now, the cost model for this transform is rather overly strict,
so this will basically never fire. We tally all (over all preds)
the selects needed to the NumBonusInsts

Differential Revision: https://reviews.llvm.org/D139275

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Revert "[SimplifyCFG] `FoldBranchToCommonDest()`: deal with mismatched IV's in PHI's in common successor block"

This reverts commit 1bd0b82e508d049efdb07f4f8a342f35818df341, since it leads to
miscom

Revert "[SimplifyCFG] `FoldBranchToCommonDest()`: deal with mismatched IV's in PHI's in common successor block"

This reverts commit 1bd0b82e508d049efdb07f4f8a342f35818df341, since it leads to
miscompiles. See https://reviews.llvm.org/D139275#3993229 and
https://reviews.llvm.org/D139275#4001580.

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[SimplifyCFG] `FoldBranchToCommonDest()`: deal with mismatched IV's in PHI's in common successor block

This tries to approach the problem noted by @arsenm:
terrible codegen for `__builtin_fpclassify

[SimplifyCFG] `FoldBranchToCommonDest()`: deal with mismatched IV's in PHI's in common successor block

This tries to approach the problem noted by @arsenm:
terrible codegen for `__builtin_fpclassify()`:
https://godbolt.org/z/388zqdE37

Just because the PHI in the common successor happens to have different
incoming values for these two blocks, doesn't mean we have to give up.
It's quite easy to deal with this, we just need to produce a select:
https://alive2.llvm.org/ce/z/000srb

Now, the cost model for this transform is rather overly strict,
so this will basically never fire. We tally all (over all preds)
the selects needed to the NumBonusInsts

Differential Revision: https://reviews.llvm.org/D139275

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[NFC] Re-autogenerate checklines in a few tests being affected

[test][InstCombine] Update some test cases to use opaque pointers

These tests cases were converted using the script at
https://gist.github.com/nikic/98357b71fd67756b0f064c9517b62a34

Differential Re

[test][InstCombine] Update some test cases to use opaque pointers

These tests cases were converted using the script at
https://gist.github.com/nikic/98357b71fd67756b0f064c9517b62a34

Differential Revision: https://reviews.llvm.org/D135094

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[Pipelines] Introduce DAE after ArgumentPromotion

The ArgumentPromotion pass uses Mem2Reg promotion at the end to cutting
down generated `alloca` instructions as well as meaningless `store`s and
thi

[Pipelines] Introduce DAE after ArgumentPromotion

The ArgumentPromotion pass uses Mem2Reg promotion at the end to cutting
down generated `alloca` instructions as well as meaningless `store`s and
this behavior can leave unused (dead) arguments. To eliminate the dead
arguments and therefore let the DeadCodeElimination remove becoming dead
inserted `GEP`s as well as `load`s and `cast`s in the callers, the
DeadArgumentElimination pass should be run after the ArgumentPromotion
one.

Differential Revision: https://reviews.llvm.org/D128830

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Revert "[Pipelines] Introduce DAE after ArgumentPromotion"

This reverts commit b10a341aa5b0b93b9175a8f11efc9a0955ab361e.

This commit exposes the pre-existing https://github.com/llvm/llvm-project/is

Revert "[Pipelines] Introduce DAE after ArgumentPromotion"

This reverts commit b10a341aa5b0b93b9175a8f11efc9a0955ab361e.

This commit exposes the pre-existing https://github.com/llvm/llvm-project/issues/56503 in some edge cases. Will fix that and then reland this.

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[Pipelines] Introduce DAE after ArgumentPromotion

The ArgumentPromotion pass uses Mem2Reg promotion at the end to cutting
down generated `alloca` instructions as well as meaningless `store`s and
thi

[Pipelines] Introduce DAE after ArgumentPromotion

The ArgumentPromotion pass uses Mem2Reg promotion at the end to cutting
down generated `alloca` instructions as well as meaningless `store`s and
this behavior can leave unused (dead) arguments. To eliminate the dead
arguments and therefore let the DeadCodeElimination remove becoming dead
inserted `GEP`s as well as `load`s and `cast`s in the callers, the
DeadArgumentElimination pass should be run after the ArgumentPromotion
one.

Differential Revision: https://reviews.llvm.org/D128830

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Revert "[Pipelines] Introduce DAE after ArgumentPromotion"

The commit breaks the compiler when a function is used as a function
parameter (hm... for a function from the standard C library?):

```
st

Revert "[Pipelines] Introduce DAE after ArgumentPromotion"

The commit breaks the compiler when a function is used as a function
parameter (hm... for a function from the standard C library?):

```
static float strtof(char *, char *) {}
void a() { strtof(a, 0); }
```

This reverts commit 879f5118fc74657e4a5c4eff6810098e1eed75ac.

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[Pipelines] Introduce DAE after ArgumentPromotion

The ArgumentPromotion pass uses Mem2Reg promotion at the end to cutting
down generated `alloca` instructions as well as meaningless `store`s and
thi

[Pipelines] Introduce DAE after ArgumentPromotion

The ArgumentPromotion pass uses Mem2Reg promotion at the end to cutting
down generated `alloca` instructions as well as meaningless `store`s and
this behavior can leave unused (dead) arguments. To eliminate the dead
arguments and therefore let the DeadCodeElimination remove becoming dead
inserted `GEP`s as well as `load`s and `cast`s in the callers, the
DeadArgumentElimination pass should be run after the ArgumentPromotion
one.

Differential Revision: https://reviews.llvm.org/D128830

show more ...

Revert "[Pipelines] Introduce DAE after ArgumentPromotion"

This reverts commit 3f20dcbf708cb23f79c4866d8285a8ae7bd885de.

[Pipelines] Introduce DAE after ArgumentPromotion

The ArgumentPromotion pass uses Mem2Reg promotion at the end to cutting
down generated `alloca` instructions as well as meaningless `store`s and
thi

[Pipelines] Introduce DAE after ArgumentPromotion

The ArgumentPromotion pass uses Mem2Reg promotion at the end to cutting
down generated `alloca` instructions as well as meaningless `store`s and
this behavior can leave unused (dead) arguments. To eliminate the dead
arguments and therefore let the DeadCodeElimination remove becoming dead
inserted `GEP`s as well as `load`s and `cast`s in the callers, the
DeadArgumentElimination pass should be run after the ArgumentPromotion
one.

Differential Revision: https://reviews.llvm.org/D128830

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[Attributes] Remove nonnull from UB-implying attributes

From LangRef:

> if the parameter or return pointer is null, poison value is
> returned or passed instead. The nonnull attribute should be
> c

[Attributes] Remove nonnull from UB-implying attributes

From LangRef:

> if the parameter or return pointer is null, poison value is
> returned or passed instead. The nonnull attribute should be
> combined with the noundef attribute to ensure a pointer is not
> null or otherwise the behavior is undefined.

Dropping noundef is sufficient to prevent UB. Including nonnull
in this method just muddies the semantics.

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[DAE] Adjust param/arg attributes when changing parameter to undef

In DeadArgumentElimination pass, if a function's argument is never used, corresponding caller's parameter can be changed to undef.

[DAE] Adjust param/arg attributes when changing parameter to undef

In DeadArgumentElimination pass, if a function's argument is never used, corresponding caller's parameter can be changed to undef. If the param/arg has attribute noundef or other related attributes, LLVM LangRef(https://llvm.org/docs/LangRef.html#parameter-attributes) says its behavior is undefined. SimplifyCFG(D97244) takes advantage of this behavior and does bad transformation on valid code.

To avoid this undefined behavior when change caller's parameter to undef, this patch removes noundef attribute and other attributes imply noundef on param/arg.

Differential Revision: https://reviews.llvm.org/D98899

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Allow nonnull/align attribute to accept poison

Currently LLVM is relying on ValueTracking's `isKnownNonZero` to attach `nonnull`, which can return true when the value is poison.
To make the semantic

Allow nonnull/align attribute to accept poison

Currently LLVM is relying on ValueTracking's `isKnownNonZero` to attach `nonnull`, which can return true when the value is poison.
To make the semantics of `nonnull` consistent with the behavior of `isKnownNonZero`, this makes the semantics of `nonnull` to accept poison, and return poison if the input pointer isn't null.
This makes many transformations like below legal:

```
%p = gep inbounds %x, 1 ; % p is non-null pointer or poison
call void @f(%p) ; instcombine converts this to call void @f(nonnull %p)
```

Instead, this semantics makes propagation of `nonnull` to caller illegal.
The reason is that, passing poison to `nonnull` does not immediately raise UB anymore, so such program is still well defined, if the callee does not use the argument.
Having `noundef` attribute there re-allows this.

```
define void @f(i8* %p) { ; functionattr cannot mark %p nonnull here anymore
call void @g(i8* nonnull %p) ; .. because @g never raises UB if it never uses %p.
ret void
}
```

Another attribute that needs to be updated is `align`. This patch updates the semantics of align to accept poison as well.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D90529

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[InstCombine] Simplify calls with "returned" attribute

If a call argument has the "returned" attribute, we can simplify
the call to the value of that argument. This was already partially
handled by

[InstCombine] Simplify calls with "returned" attribute

If a call argument has the "returned" attribute, we can simplify
the call to the value of that argument. This was already partially
handled by InstSimplify/InstCombine for the case where the argument
is an integer constant, and the result is thus known via known bits.
The non-constant (or non-int) argument cases weren't handled though.

This previously landed as an InstSimplify transform, but was reverted
due to assertion failures when compiling the Linux kernel. The reason
is that simplifying a call to another call breaks assumptions in
call graph updating during inlining. As the code is not easy to fix,
and there is no particularly strong motivation for having this in
InstSimplify, the transform is only performed in InstCombine instead.

Differential Revision: https://reviews.llvm.org/D75815

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Revert "[InstSimplify] Simplify calls with "returned" attribute"

This reverts commit 45555c381926050bc45a3372b1af0e15650371b6.
Causes clang crashes in some causes, see comments on
https://reviews.ll

Revert "[InstSimplify] Simplify calls with "returned" attribute"

This reverts commit 45555c381926050bc45a3372b1af0e15650371b6.
Causes clang crashes in some causes, see comments on
https://reviews.llvm.org/D75815 for details (including
repro steps).

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[InstSimplify] Simplify calls with "returned" attribute

If a call argument has the "returned" attribute, we can simplify
the call to the value of that argument. The "-inst-simplify" pass
already han

[InstSimplify] Simplify calls with "returned" attribute

If a call argument has the "returned" attribute, we can simplify
the call to the value of that argument. The "-inst-simplify" pass
already handled this for the constant integer argument case via
known bits, which is invoked in SimplifyInstruction. However,
non-constant (or non-int) arguments are not handled at all right now.

This addresses one of the regressions from D75801.

Differential Revision: https://reviews.llvm.org/D75815

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[InstCombine] Regenerate test checks; NFC

Revert "[InstCombine] keep assumption before sinking calls"

Summary:
This reverts commit c3b06d0c393e533eab712922911d14e5a079fa5d.

Reason for revert: Caused miscompiles when inserting assume for un

Revert "[InstCombine] keep assumption before sinking calls"

Summary:
This reverts commit c3b06d0c393e533eab712922911d14e5a079fa5d.

Reason for revert: Caused miscompiles when inserting assume for undef.

Also adds a test to prevent similar breakage in future.

Fixes PR44154.

Reviewers: rnk, jdoerfert, efriedma, xbolva00

Reviewed By: rnk

Subscribers: thakis, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70933

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