[NFC][DebugInfo] Use iterator-flavour getFirstNonPHI at many call-sites (#123737)

As part of the "RemoveDIs" project, BasicBlock::iterator now carries a
debug-info bit that's needed when getFirstNo

[NFC][DebugInfo] Use iterator-flavour getFirstNonPHI at many call-sites (#123737)

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 getFirstNonPHI use the iterator-returning version.

This patch changes a bunch of call-sites calling getFirstNonPHI to use
getFirstNonPHIIt, which returns an iterator. All these call sites are
where it's obviously safe to fetch the iterator then dereference it. A
follow-up patch will contain less-obviously-safe changes.

We'll eventually deprecate and remove the instruction-pointer
getFirstNonPHI, but not before adding concise documentation of what
considerations are needed (very few).

---------

Co-authored-by: Stephen Tozer <Melamoto@gmail.com>

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[nfc][llvm] Replace pointer cast functions in PointerUnion by llvm casting functions.

This patch replaces the uses of PointerUnion.is function by llvm::isa,
PointerUnion.get function by llvm::cast,

[nfc][llvm] Replace pointer cast functions in PointerUnion by llvm casting functions.

This patch replaces the uses of PointerUnion.is function by llvm::isa,
PointerUnion.get function by llvm::cast, and PointerUnion.dyn_cast by
llvm::dyn_cast_if_present. This is according to the FIXME in
the definition of the class PointerUnion.

This patch does not remove them as they are being used in other
subprojects.

Reviewed By: mehdi_amini

Differential Revision: https://reviews.llvm.org/D148449

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Reland "[Windows SEH]: HARDWARE EXCEPTION HANDLING (MSVC -EHa) - Part 2"

This reverts commit db6a979ae82410e42430e47afa488936ba8e3025.

Reland D102817 without any change. The previous revert was a m

Reland "[Windows SEH]: HARDWARE EXCEPTION HANDLING (MSVC -EHa) - Part 2"

This reverts commit db6a979ae82410e42430e47afa488936ba8e3025.

Reland D102817 without any change. The previous revert was a mistake.

Differential Revision: https://reviews.llvm.org/D102817

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Cleanup unwind table emission code a bit.

This change removes the `tidyLandingPads` function, which previously
had a few responsibilities:

1. Dealing with the deletion of an invoke, after MachineFu

Cleanup unwind table emission code a bit.

This change removes the `tidyLandingPads` function, which previously
had a few responsibilities:

1. Dealing with the deletion of an invoke, after MachineFunction lowering.
2. Dealing with the deletion of a landing pad BB, after MachineFunction lowering.
3. Cleaning up the type-id list generated by `MachineFunction::addLandingPad`.

Case 3 has been fixed in the generator, and the others are now handled
during table emission.

This change also removes `MachineFunction`'s `addCatchTypeInfo`,
`addFilterTypeInfo`, and `addCleanup` helper fns, as they had a single
caller, and being outlined didn't make it simpler.

Finally, as calling `tidyLandingPads` was effectively the only thing
`DwarfCFIExceptionBase` did, that class has been eliminated.

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Revert "[Windows SEH]: HARDWARE EXCEPTION HANDLING (MSVC -EHa) - Part 2"

This reverts commit 1a949c871ab4a6b6d792849d3e8c0fa6958d27f5.

[Windows SEH]: HARDWARE EXCEPTION HANDLING (MSVC -EHa) - Part 2

This patch is the Part-2 (BE LLVM) implementation of HW Exception handling.
Part-1 (FE Clang) was committed in 797ad701522988e21249528

[Windows SEH]: HARDWARE EXCEPTION HANDLING (MSVC -EHa) - Part 2

This patch is the Part-2 (BE LLVM) implementation of HW Exception handling.
Part-1 (FE Clang) was committed in 797ad701522988e212495285dade8efac41a24d4.

This new feature adds the support of Hardware Exception for Microsoft Windows
SEH (Structured Exception Handling).

Compiler options:
For clang-cl.exe, the option is -EHa, the same as MSVC.
For clang.exe, the extra option is -fasync-exceptions,
plus -triple x86_64-windows -fexceptions and -fcxx-exceptions as usual.

NOTE:: Without the -EHa or -fasync-exceptions, this patch is a NO-DIFF change.

The rules for C code:
For C-code, one way (MSVC approach) to achieve SEH -EHa semantic is to follow three rules:
First, no exception can move in or out of _try region., i.e., no "potential faulty
instruction can be moved across _try boundary.
Second, the order of exceptions for instructions 'directly' under a _try must be preserved
(not applied to those in callees).
Finally, global states (local/global/heap variables) that can be read outside of _try region
must be updated in memory (not just in register) before the subsequent exception occurs.

The impact to C++ code:
Although SEH is a feature for C code, -EHa does have a profound effect on C++
side. When a C++ function (in the same compilation unit with option -EHa ) is
called by a SEH C function, a hardware exception occurs in C++ code can also
be handled properly by an upstream SEH _try-handler or a C++ catch(...).
As such, when that happens in the middle of an object's life scope, the dtor
must be invoked the same way as C++ Synchronous Exception during unwinding process.

Design:
A natural way to achieve the rules above in LLVM today is to allow an EH edge
added on memory/computation instruction (previous iload/istore idea) so that
exception path is modeled in Flow graph preciously. However, tracking every
single memory instruction and potential faulty instruction can create many
Invokes, complicate flow graph and possibly result in negative performance
impact for downstream optimization and code generation. Making all
optimizations be aware of the new semantic is also substantial.

This design does not intend to model exception path at instruction level.
Instead, the proposed design tracks and reports EH state at BLOCK-level to
reduce the complexity of flow graph and minimize the performance-impact on CPP
code under -EHa option.
One key element of this design is the ability to compute State number at
block-level. Our algorithm is based on the following rationales:

A _try scope is always a SEME (Single Entry Multiple Exits) region as jumping
into a _try is not allowed. The single entry must start with a seh_try_begin()
invoke with a correct State number that is the initial state of the SEME.
Through control-flow, state number is propagated into all blocks. Side exits
marked by seh_try_end() will unwind to parent state based on existing SEHUnwindMap[].
Note side exits can ONLY jump into parent scopes (lower state number).
Thus, when a block succeeds various states from its predecessors, the lowest
State triumphs others. If some exits flow to unreachable, propagation on those
paths terminate, not affecting remaining blocks.
For CPP code, object lifetime region is usually a SEME as SEH _try.
However there is one rare exception: jumping into a lifetime that has Dtor but
has no Ctor is warned, but allowed:

Warning: jump bypasses variable with a non-trivial destructor

In that case, the region is actually a MEME (multiple entry multiple exits).
Our solution is to inject a eha_scope_begin() invoke in the side entry block to
ensure a correct State.
Implementation:
Part-1: Clang implementation (already in):
Please see commit 797ad701522988e212495285dade8efac41a24d4).

Part-2 : LLVM implementation described below.

For both C++ & C-code, the state of each block is computed at the same place in
BE (WinEHPreparing pass) where all other EH tables/maps are calculated.
In addition to _scope_begin & _scope_end, the computation of block state also
rely on the existing State tracking code (UnwindMap and InvokeStateMap).

For both C++ & C-code, the state of each block with potential trap instruction
is marked and reported in DAG Instruction Selection pass, the same place where
the state for -EHsc (synchronous exceptions) is done.
If the first instruction in a reported block scope can trap, a Nop is injected
before this instruction. This nop is needed to accommodate LLVM Windows EH
implementation, in which the address in IPToState table is offset by +1.
(note the purpose of that is to ensure the return address of a call is in the
same scope as the call address.

The handler for catch(...) for -EHa must handle HW exception. So it is
'adjective' flag is reset (it cannot be IsStdDotDot (0x40) that only catches
C++ exceptions).
Suppress push/popTerminate() scope (from noexcept/noTHrow) so that HW
exceptions can be passed through.

Original llvm-dev [RFC] discussions can be found in these two threads below:
https://lists.llvm.org/pipermail/llvm-dev/2020-March/140541.html
https://lists.llvm.org/pipermail/llvm-dev/2020-April/141338.html

Differential Revision: https://reviews.llvm.org/D102817/new/

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[Alignment][NFC] Use Align in MCStreamer::emitValueToAlignment

Differential Revision: https://reviews.llvm.org/D138674

[MC] De-capitalize SwitchSection. NFC

Add SwitchSection to return switchSection. The API will be removed soon.

[MC] De-capitalize MCStreamer functions

Follow-up to c031378ce01b8485ba0ef486654bc9393c4ac024 .
The class is mostly consistent now.

[ARM] [MC] Add support for writing ARM WinEH unwind info

This includes .seh_* directives for generating it from assembly.
It is designed fairly similarly to the ARM64 handling.

For .seh_handler dir

[ARM] [MC] Add support for writing ARM WinEH unwind info

This includes .seh_* directives for generating it from assembly.
It is designed fairly similarly to the ARM64 handling.

For .seh_handler directives, such as
".seh_handler __C_specific_handler, @except" (which is supported
on x86_64 and aarch64 so far), the "@except" bit doesn't work in
ARM assembly, as '@' is used as a comment character (on all current
platforms).

Allow using '%' instead of '@' for this purpose. This convention
is used by GAS in similar contexts already,
e.g. [1]:

Note on targets where the @ character is the start of a comment
(eg ARM) then another character is used instead. For example the
ARM port uses the % character.

In practice, this unfortunately means that all such .seh_handler
directives will need ifdefs for ARM.

Contrary to ARM64, on ARM, it's quite common that we can't evaluate
e.g. the function length at this point, due to instructions whose
length is finalized later. (Also, inline jump tables end with
a ".p2align 1".)

If unable to to evaluate the function length immediately, emit
it as an MCExpr instead. If we'd implement splitting the unwind
info for a function (which isn't implemented for ARM64 yet either),
we wouldn't know whether we need to split it though.

Avoid calling getFrameIndexOffset() on an unset
FuncInfo.UnwindHelpFrameIdx, to avoid triggering asserts in the
preexisting testcase CodeGen/ARM/Windows/wineh-basic.ll. (Once
MSVC exception handling is fully implemented, those changes
can be reverted.)

[1] https://sourceware.org/binutils/docs/as/Section.html#Section

Differential Revision: https://reviews.llvm.org/D125645

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[MC] Lower case the first letter of EmitCOFF* EmitWin* EmitCV*. NFC

Cleanup includes: DebugInfo & CodeGen

Discourse thread: https://discourse.llvm.org/t/include-what-you-use-include-cleanup
Differential Revision: https://reviews.llvm.org/D121332

[CodeGen] Use = default (NFC)

Identified with modernize-use-equals-default

Fix SEH table addresses for Windows

Issue Details:
The addresses for SEH tables for Windows are incorrect as 1 was unconditionally being added to all addresses. +1 is required for the SEH end addres

Fix SEH table addresses for Windows

Issue Details:
The addresses for SEH tables for Windows are incorrect as 1 was unconditionally being added to all addresses. +1 is required for the SEH end address (as it is exclusive), but the SEH start addresses is inclusive and so should be used as-is.

In the IP2State tables, the addresses are +1 for AMD64 to handle the return address for a call being after the actual call instruction but are as-is for ARM and ARM64 as the `StateFromIp` function in the VC runtime automatically takes this into account and adjusts the address that is it looking up.

Fix Details:
* Split the `getLabel` function into two: `getLabel` (used for the SEH start address and ARM+ARM64 IP2State addresses) and `getLabelPlusOne` (for the SEH end address, and AMD64 IP2State addresses).

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D107784

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Add ehcont section support

In the future Windows will enable Control-flow Enforcement Technology (CET aka shadow stacks). To protect the path where the context is updated during exception handling,

Add ehcont section support

In the future Windows will enable Control-flow Enforcement Technology (CET aka shadow stacks). To protect the path where the context is updated during exception handling, the binary is required to enumerate valid unwind entrypoints in a dedicated section which is validated when the context is being set during exception handling.

This change allows llvm to generate the section that contains the appropriate symbol references in the form expected by the msvc linker.

This feature is enabled through a new module flag, ehcontguard, which was modelled on the cfguard flag.

The change includes a test that when the module flag is enabled the section is correctly generated.

The set of exception continuation information includes returns from exceptional control flow (catchret in llvm).

In order to collect catchret we:
1) Includes an additional flag on machine basic blocks to indicate that the given block is the target of a catchret operation,
2) Introduces a new machine function pass to insert and collect symbols at the start of each block, and
3) Combines these targets with the other EHCont targets that were already being collected.

Change originally authored by Daniel Frampton <dframpto@microsoft.com>

For more details, see MSVC documentation for `/guard:ehcont`
https://docs.microsoft.com/en-us/cpp/build/reference/guard-enable-eh-continuation-metadata

Reviewed By: pengfei

Differential Revision: https://reviews.llvm.org/D94835

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Reapply "[CodeGen] [WinException] Only produce handler data at the end of the function if needed"

This reapplies 36c64af9d7f97414d48681b74352c9684077259b in updated
form.

Emit the xdata for each fu

Reapply "[CodeGen] [WinException] Only produce handler data at the end of the function if needed"

This reapplies 36c64af9d7f97414d48681b74352c9684077259b in updated
form.

Emit the xdata for each function at .seh_endproc. This keeps the
exact same output header order for most code generated by the LLVM
CodeGen layer. (Sections still change order for code built from
assembly where functions lack an explicit .seh_handlerdata
directive, and functions with chained unwind info.)

The practical effect should be that assembly output lacks
superfluous ".seh_handlerdata; .text" pairs at the end of functions
that don't handle exceptions, which allows such functions to use
the AArch64 packed unwind format again.

Differential Revision: https://reviews.llvm.org/D87448

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[SVE] Return StackOffset for TargetFrameLowering::getFrameIndexReference.

To accommodate frame layouts that have both fixed and scalable objects
on the stack, describing a stack location or offset u

[SVE] Return StackOffset for TargetFrameLowering::getFrameIndexReference.

To accommodate frame layouts that have both fixed and scalable objects
on the stack, describing a stack location or offset using a pointer + uint64_t
is not sufficient. For this reason, we've introduced the StackOffset class,
which models both the fixed- and scalable sized offsets.

The TargetFrameLowering::getFrameIndexReference is made to return a StackOffset,
so that this can be used in other interfaces, such as to eliminate frame indices
in PEI or to emit Debug locations for variables on the stack.

This patch is purely mechanical and doesn't change the behaviour of how
the result of this function is used for fixed-sized offsets. The patch adds
various checks to assert that the offset has no scalable component, as frame
offsets with a scalable component are not yet supported in various places.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D90018

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Revert "[CodeGen] [WinException] Only produce handler data at the end of the function if needed"

This caused an explosion in ICF times during linking on Windows when libfuzzer
instrumentation is ena

Revert "[CodeGen] [WinException] Only produce handler data at the end of the function if needed"

This caused an explosion in ICF times during linking on Windows when libfuzzer
instrumentation is enabled. For a small binary we see ICF time go from ~0 to
~10 s. For a large binary it goes from ~1 s to forevert (I gave up after 30
minutes).

See comment on the code review.

> If we are going to write handler data (that is written as variable
> length data following after the unwind info in .xdata), we need to
> emit the handler data immediately, but for cases where no such
> info is going to be written, skip emitting it right away. (Unwind
> info for all remaining functions that hasn't gotten it emitted
> directly is emitted at the end.)
>
> This does slightly change the ordering of sections (triggering a
> bunch of updates to DebugInfo/COFF tests), but the change should be
> benign.
>
> This also matches GCC's assembly output, which doesn't output
> .seh_handlerdata unless it actually is needed.
>
> For ARM64, the unwind info can be packed into the runtime function
> entry itself (leaving no data in the .xdata section at all), but
> that can only be done if there's no follow-on data in the .xdata
> section. If emission of the unwind info is triggered via
> EmitWinEHHandlerData (or the .seh_handlerdata directive), which
> implicitly switches to the .xdata section, there's a chance of the
> caller wanting to pass further data there, so the packed format
> can't be used in that case.
>
> Differential Revision: https://reviews.llvm.org/D87448

This reverts commit 36c64af9d7f97414d48681b74352c9684077259b.

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Rename EHPersonality::MSVC_Win64SEH to EHPersonality::MSVC_TableSEH. NFC.

The types of SEH aren't x86(-32) vs x64 but rather stack-based exception chaining
vs table-based exception handling. x86-32

Rename EHPersonality::MSVC_Win64SEH to EHPersonality::MSVC_TableSEH. NFC.

The types of SEH aren't x86(-32) vs x64 but rather stack-based exception chaining
vs table-based exception handling. x86-32 is the only arch for which Windows
uses the former. 32-bit ARM would use what is called Win64SEH today, which
is a bit confusing so instead let's just rename it to be a bit more clear.

Reviewed By: compnerd, rnk

Differential Revision: https://reviews.llvm.org/D90117

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[CodeGen] [WinException] Only produce handler data at the end of the function if needed

If we are going to write handler data (that is written as variable
length data following after the unwind info

[CodeGen] [WinException] Only produce handler data at the end of the function if needed

If we are going to write handler data (that is written as variable
length data following after the unwind info in .xdata), we need to
emit the handler data immediately, but for cases where no such
info is going to be written, skip emitting it right away. (Unwind
info for all remaining functions that hasn't gotten it emitted
directly is emitted at the end.)

This does slightly change the ordering of sections (triggering a
bunch of updates to DebugInfo/COFF tests), but the change should be
benign.

This also matches GCC's assembly output, which doesn't output
.seh_handlerdata unless it actually is needed.

For ARM64, the unwind info can be packed into the runtime function
entry itself (leaving no data in the .xdata section at all), but
that can only be done if there's no follow-on data in the .xdata
section. If emission of the unwind info is triggered via
EmitWinEHHandlerData (or the .seh_handlerdata directive), which
implicitly switches to the .xdata section, there's a chance of the
caller wanting to pass further data there, so the packed format
can't be used in that case.

Differential Revision: https://reviews.llvm.org/D87448

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[CodeGen] [WinException] Remove a redundant explicit section switch for aarch64

The following EmitWinEHHandlerData() implicitly switches to .xdata, just
like on x86_64.

This became orphaned from th

[CodeGen] [WinException] Remove a redundant explicit section switch for aarch64

The following EmitWinEHHandlerData() implicitly switches to .xdata, just
like on x86_64.

This became orphaned from the original code requiring it in
0b61d220c9b1f0 / https://reviews.llvm.org/D61095.

Differential Revision: https://reviews.llvm.org/D87447

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TargetLowering.h - remove unnecessary TargetMachine.h include. NFC

Replace with forward declaration and move dependency down to source files that actually need it.

Both TargetLowering.h and TargetM

TargetLowering.h - remove unnecessary TargetMachine.h include. NFC

Replace with forward declaration and move dependency down to source files that actually need it.

Both TargetLowering.h and TargetMachine.h are 2 of the most expensive headers (top 10) in the ClangBuildAnalyzer report when building llc.

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CodeGen: Use Register in TargetFrameLowering

[MC] Add MCStreamer::emitInt{8,16,32,64}

Similar to AsmPrinter::emitInt{8,16,32,64}.

[MCStreamer] De-capitalize EmitValue EmitIntValue{,InHex}