[MCA][RegisterFile] Consistently update the PRF in the presence of multiple writes to the same register.

My last change to the RegisterFile (PR51495) has introduced a bug in the logic
that allocates

[MCA][RegisterFile] Consistently update the PRF in the presence of multiple writes to the same register.

My last change to the RegisterFile (PR51495) has introduced a bug in the logic
that allocates physical registers in the PRF.

In some cases, this bug could have triggered a nasty unsigned wrap in the number
of allocated registers, thus resulting in mca being stuck forever in a loop of
PRF availability checks.

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[X86][MCA] Address the latest issues with MULX reported in PR51495.

It turns out that SchedWrite WriteIMulH was always assigned to the low half of
the result of a MULX (rather than to the high half)

[X86][MCA] Address the latest issues with MULX reported in PR51495.

It turns out that SchedWrite WriteIMulH was always assigned to the low half of
the result of a MULX (rather than to the high half).

To avoid confusion, this patch swaps the two MULX writes in the tablegen
definition of MULX32/64. That way, write names better describe what they
actually refer to; this also avoids further complications if in future we decide
to reuse the same MulH writes to also model other scalar integer multiply
instructions. I also had to swap the latency values for the two MULX writes to
make sure that the change is effectively an NFC. In fact, none of the existing
x86 tests were affected by this small refactoring.

This patch also fixes a bug in MCA: a wrong latency value was propagated for
instructions that perform multiple writes to a same register. This last issue
was found by Roman while testing MULX on targets that define a different latency
for the Low/High part of the result.

Differential Revision: https://reviews.llvm.org/D108727

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[MCA] [RegisterFile] Allow for skipping Defs with RegID of 0 (rather than assert(RegID) like we do before this patch).

This patch will allow developers to remove unwanted instruction Defs (most like

[MCA] [RegisterFile] Allow for skipping Defs with RegID of 0 (rather than assert(RegID) like we do before this patch).

This patch will allow developers to remove unwanted instruction Defs (most likely from within a target specific InstrPostProcess) by setting that Def's RegisterID to 0.
Differential Revision: https://reviews.llvm.org/D104433

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[MCA] Refactor the InOrderIssueStage stage. NFCI

Moved the logic that checks for RAW hazards from the InOrderIssueStage to the
RegisterFile.

Changed how the InOrderIssueStage keeps track of backend

[MCA] Refactor the InOrderIssueStage stage. NFCI

Moved the logic that checks for RAW hazards from the InOrderIssueStage to the
RegisterFile.

Changed how the InOrderIssueStage keeps track of backend stalls. Stall events
are now generated from method notifyStallEvent().

No functional change intended.

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[MCA][RegisterFile] Refactor the move elimination logic to address PR50258.

This patch lifts the restriction on the number of read/write registers for a
move elimination candidate. With this patch,

[MCA][RegisterFile] Refactor the move elimination logic to address PR50258.

This patch lifts the restriction on the number of read/write registers for a
move elimination candidate. With this patch, move elimination candidates with
exactly two reads and two writes are treated like register swap operations for
the purpose of move elimination.

This patch currently doesn't affect any upstream model. However, it should help
unblock the progress on PR50258.

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[MCA][RegisterFile] Fix register class check for move elimination (PR50265)

The register file should always check if the destination register is from a
register class that allows move elimination.

[MCA][RegisterFile] Fix register class check for move elimination (PR50265)

The register file should always check if the destination register is from a
register class that allows move elimination.

Before this change, the check on the register class was only performed in a few
very specific cases. However, it should have always been performed.
This patch fixes the issue.

Note that none of the upstream scheduling models is currently affected by this
bug, so there is no test for it. The issue was found by Roman while working on
the znver3 model. I was able to reproduce the issue locally by tweaking the
btver2 model. I then verified that this patch fixes the issue.

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[MCA] Fix for uninitialised member in constructor. NFC

[MCA] Improved handling of negative read-advance cycles.

Before this patch, register writes were always invalidated by the
RegisterFile at instruction commit stage. So,
the RegisterFile was often lo

[MCA] Improved handling of negative read-advance cycles.

Before this patch, register writes were always invalidated by the
RegisterFile at instruction commit stage. So,
the RegisterFile was often losing the knowledge about the `execute
cycle` of writes already committed. While this was not problematic
for non-delayed reads, this was sometimes leading to inaccurate read
latency computations in the presence of negative read-advance cycles.

This patch fixes the issue by changing how the RegisterFile component
internally keeps track of the `execute cycle` information of each
write. On every instruction executed, the RegisterFile gets notified
by the RetireStage, so that it can internally record the execute
cycle of each executed write.
The `execute cycle` information is stored within WriteRef itself, and
it is not invalidated when the write is committed.

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[APInt] New member function setBitVal

Differential Revision: https://reviews.llvm.org/D87033

[MCA] consistently use MCPhysReg instead of unsigned as register type. NFCI

llvm-svn: 369648

[MCA] Correctly update register definitions in the PRF after move elimination.

This patch fixes a bug where register writes performed by optimizable register
moves were sometimes wrongly treated lik

[MCA] Correctly update register definitions in the PRF after move elimination.

This patch fixes a bug where register writes performed by optimizable register
moves were sometimes wrongly treated like partial register updates. Before this
patch, llvm-mca wrongly predicted a 1.50 IPC for test reg-move-elimination-6.s
(added by this patch). With this patch, llvm-mca correctly updates the register
defintions in the PRF, and the IPC for that test is now correctly reported as 2.

llvm-svn: 354271

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[MCA] Slightly refactor method writeStartEvent in WriteState and ReadState. NFCI

This is another change in preparation for PR37494.
No functional change intended.

llvm-svn: 354261

[MCA] Moved the logic that updates register dependencies from DispatchStage to RegisterFile. NFC

DispatchStage should always delegate to an object of class RegisterFile the task
of updating data dep

[MCA] Moved the logic that updates register dependencies from DispatchStage to RegisterFile. NFC

DispatchStage should always delegate to an object of class RegisterFile the task
of updating data dependencies. ReadState and WriteState objects should not be
modified directly by DispatchStage.
This patch also renames stage IS_AVAILABLE to IS_DISPATCHED.

llvm-svn: 353170

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Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the ne

Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636

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[llvm-mca] Move llvm-mca library to llvm/lib/MCA.

Summary: See PR38731.

Reviewers: andreadb

Subscribers: mgorny, javed.absar, tschuett, gbedwell, andreadb, RKSimon, llvm-commits

Differential Revi

[llvm-mca] Move llvm-mca library to llvm/lib/MCA.

Summary: See PR38731.

Reviewers: andreadb

Subscribers: mgorny, javed.absar, tschuett, gbedwell, andreadb, RKSimon, llvm-commits

Differential Revision: https://reviews.llvm.org/D55557

llvm-svn: 349332

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