[AMDGPU] Restore SP from saved-FP or saved-BP (#124007)

Currently, the AMDGPU backend bumps the Stack Pointer
by fixed size offsets in the prolog of device functions, and
restores it by the same

[AMDGPU] Restore SP from saved-FP or saved-BP (#124007)

Currently, the AMDGPU backend bumps the Stack Pointer
by fixed size offsets in the prolog of device functions, and
restores it by the same amount in the epilog.
Prolog:
sp += frameSize

Epilog:
sp -= frameSize

If a function has dynamic stack realignment,
Prolog:
sp += frameSize + max_alignment

Epilog:
sp -= frameSize + max_alignment

These calculations are not optimal in case of dynamic
stack realignment, and completely fail in case of
dynamic stack readjustment.
This patch uses the saved Frame Pointer to restore SP.
Prolog:
fp = sp
sp += frameSize

Epilog:
sp = fp

In case of dynamic stack realignment, SP is restored from
the saved Base Pointer.
Prolog:
fp = sp + (max_alignment - 1)
fp = fp & (-max_alignment)
bp = sp
sp += frameSize + max_alignment

Epilog:
sp = bp

(Note: The presence of BP has been enforced in case of any
dynamic stack realignment.)

---------

Co-authored-by: Pravin Jagtap <Pravin.Jagtap@amd.com>
Co-authored-by: Matt Arsenault <arsenm2@gmail.com>

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[AMDGPU] PromoteAlloca - bail always if load/store is volatile (#73228)

This change is addressing case where alloca size is the same as
load/store size.

Reapply "[CodeGen]Allow targets to use target specific COPY instructions for live range splitting"

This reverts commit a496c8be6e638ae58bb45f13113dbe3a4b7b23fd.

The workaround in c26dfc81e254c78dc2

Reapply "[CodeGen]Allow targets to use target specific COPY instructions for live range splitting"

This reverts commit a496c8be6e638ae58bb45f13113dbe3a4b7b23fd.

The workaround in c26dfc81e254c78dc23579cf3d1336f77249e1f6 should work
around the underlying problem with SUBREG_TO_REG.

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Revert "[CodeGen]Allow targets to use target specific COPY instructions for live range splitting"

And dependent commits.

Details in D150388.

This reverts commit 825b7f0ca5f2211ec3c93139f98d1e24048

Revert "[CodeGen]Allow targets to use target specific COPY instructions for live range splitting"

And dependent commits.

Details in D150388.

This reverts commit 825b7f0ca5f2211ec3c93139f98d1e24048c225c.
This reverts commit 7a98f084c4d121244ef7286bc6503b6a181d446e.
This reverts commit b4a62b1fa546312d882fa12dfdcd015177d66826.
This reverts commit b7836d856206ec39509d42529f958c920368166b.

No conflicts in the code, few tests had conflicts in autogenerated CHECKs:
llvm/test/CodeGen/Thumb2/mve-float32regloops.ll
llvm/test/CodeGen/AMDGPU/fix-frame-reg-in-custom-csr-spills.ll

Reviewed By: alexfh

Differential Revision: https://reviews.llvm.org/D156381

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[AMDGPU] Use SSAUpdater in PromoteAlloca

This allows PromoteAlloca to not be reliant on a second SROA run to remove the alloca completely. It just does the full transformation directly.

Note Promot

[AMDGPU] Use SSAUpdater in PromoteAlloca

This allows PromoteAlloca to not be reliant on a second SROA run to remove the alloca completely. It just does the full transformation directly.

Note PromoteAlloca is still reliant on SROA running first to
canonicalize the IR. For instance, PromoteAlloca will no longer handle aggregate types because those should be simplified by SROA before reaching the pass.

Reviewed By: #amdgpu, arsenm

Differential Revision: https://reviews.llvm.org/D152706

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[AMDGPU][SILowerSGPRSpills] Spill SGPRs to virtual VGPRs

Currently, the custom SGPR spill lowering pass spills
SGPRs into physical VGPR lanes and the remaining VGPRs
are used by regalloc for vector

[AMDGPU][SILowerSGPRSpills] Spill SGPRs to virtual VGPRs

Currently, the custom SGPR spill lowering pass spills
SGPRs into physical VGPR lanes and the remaining VGPRs
are used by regalloc for vector regclass allocation.
This imposes many restrictions that we ended up with
unsuccessful SGPR spilling when there won't be enough
VGPRs and we are forced to spill the leftover into
memory during PEI. The custom spill handling during PEI
has many edge cases and often breaks the compiler time
to time.

This patch implements spilling SGPRs into virtual VGPR
lanes. Since we now split the register allocation for
SGPRs and VGPRs, the virtual registers introduced for
the spill lanes would get allocated automatically in
the subsequent regalloc invocation for VGPRs.

Spill to virtual registers will always be successful,
even in the high-pressure situations, and hence it avoids
most of the edge cases during PEI. We are now left with
only the custom SGPR spills during PEI for special registers
like the frame pointer which is an unproblematic case.

Differential Revision: https://reviews.llvm.org/D124196

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Revert "[AMDGPU] Use SSAUpdater in PromoteAlloca"

This reverts commit 091bfa76db64fbe96d0e53d99b2068cc05f6aa16.

[AMDGPU] Use SSAUpdater in PromoteAlloca

This allows PromoteAlloca to not be reliant on a second SROA run to remove the alloca completely. It just does the full transformation directly.

Note Promot

[AMDGPU] Use SSAUpdater in PromoteAlloca

This allows PromoteAlloca to not be reliant on a second SROA run to remove the alloca completely. It just does the full transformation directly.

Note PromoteAlloca is still reliant on SROA running first to
canonicalize the IR. For instance, PromoteAlloca will no longer handle aggregate types because those should be simplified by SROA before reaching the pass.

Reviewed By: #amdgpu, arsenm

Differential Revision: https://reviews.llvm.org/D152706

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Revert "[AMDGPU][SILowerSGPRSpills] Spill SGPRs to virtual VGPRs"

This reverts commit 40ba0942e2ab1107f83aa5a0ee5ae2980bf47b1a.

[AMDGPU][SILowerSGPRSpills] Spill SGPRs to virtual VGPRs

Currently, the custom SGPR spill lowering pass spills
SGPRs into physical VGPR lanes and the remaining VGPRs
are used by regalloc for vector

[AMDGPU][SILowerSGPRSpills] Spill SGPRs to virtual VGPRs

Currently, the custom SGPR spill lowering pass spills
SGPRs into physical VGPR lanes and the remaining VGPRs
are used by regalloc for vector regclass allocation.
This imposes many restrictions that we ended up with
unsuccessful SGPR spilling when there won't be enough
VGPRs and we are forced to spill the leftover into
memory during PEI. The custom spill handling during PEI
has many edge cases and often breaks the compiler time
to time.

This patch implements spilling SGPRs into virtual VGPR
lanes. Since we now split the register allocation for
SGPRs and VGPRs, the virtual registers introduced for
the spill lanes would get allocated automatically in
the subsequent regalloc invocation for VGPRs.

Spill to virtual registers will always be successful,
even in the high-pressure situations, and hence it avoids
most of the edge cases during PEI. We are now left with
only the custom SGPR spills during PEI for special registers
like the frame pointer which isn an unproblematic case.

This patch also implements the whole wave spills which
might occur if RA spills any live range of virtual registers
involved in the whole wave operations. Earlier, we had
been hand-picking registers for such machine operands.
But now with SGPR spills into virtual VGPR lanes, we are
exposing them to the allocator.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D124196

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[AMDGPU][SIFrameLowering] Use the right frame register in CSR spills

Unlike the callee-saved VGPR spill instructions emitted by
`PEI::spillCalleeSavedRegs`, the CS VGPR spills inserted during
emitPr

[AMDGPU][SIFrameLowering] Use the right frame register in CSR spills

Unlike the callee-saved VGPR spill instructions emitted by
`PEI::spillCalleeSavedRegs`, the CS VGPR spills inserted during
emitPrologue/emitEpilogue require the exec bits flipping to avoid
clobbering the inactive lanes of VGPRs used for SGPR spilling.
Currently, these spill instructions are referenced from the SP at
function entry and when the callee performs a stack realignment,
they ended up getting incorrect stack offsets. Even if we try to
adjust the offsets, the FP-SP becomes a runtime entity with dynamic
stack realignment and the offsets would still be inaccurate.

To fix it, use FP as the frame base in the spill instructions
whenever the function has FP. The offsets obtained for the CS
objects would always be the right values from FP.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D134949

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