Currently, a node and its users are added back to the worklist in reverse topological order after it is combined. This diff changes that order to be topological. This is part of a larger migration to get the DAGCombiner to process nodes in topological order.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D127115

This reverts commit e69fa03ddd85812be3143d79a0359c3e8d43bd45.

This patch lead to build time outs on the AMDGPU OpenMP runtime
buildbot.

Currently, a node and its users are added back to the worklist in reverse topological order after it is combined. This diff changes that order to be topological. This is part of a larger migration to get the DAGCombiner to process nodes in topological order.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D127115

This reverts commit 122efef8ee9be57055d204d52c38700fe933c033.

- Patch fixed to not reuse definitions from predecessors in EH landing pads.
- Late review suggestions (by MaskRay) have been addressed.
- M68k/pipeline.ll test updated.
- Init captures added in processBlock() to avoid capturing structured bindings.
- RISCV has this disabled for now.

Original commit message:

A new pass MachineLateInstrsCleanup is added to be run after PEI.

This is a simple pass that removes redundant and identical instructions
whenever found by scanning the MF once while keeping track of register
definitions in a map. These instructions are typically immediate loads
resulting from rematerialization, and address loads emitted by target in
eliminateFrameInde().

This is enabled by default, but a target could easily disable it by means of
'disablePass(&MachineLateInstrsCleanupID);'.

This late cleanup is naturally not "optimal" in removing instructions as it
is done by looking at phys-regs, but still quite effective. It would be
desirable to improve other parts of CodeGen and avoid these redundant
instructions in the first place, but there are no ideas for this yet.

Differential Revision: https://reviews.llvm.org/D123394

Reviewed By: RKSimon, foad, craig.topper, arsenm, asb

This reverts commit 17db0de330f943833296ae72e26fa988bba39cb3.

Some more bots got broken - need to investigate.

Init captures added in processBlock() to avoid capturing structured bindings,
which caused the build problems (with clang).

RISCV has this disabled for now until problems relating to post RA pseudo
expansions are resolved.

Temporarily revert and fix buildbot failure.

This reverts commit 6d12599fd4134c1da63198c74a25490d28c733f6.

A new pass MachineLateInstrsCleanup is added to be run after PEI.

This is a simple pass that removes redundant and identical instructions
whenever found by scanning the MF once while keeping track of register
definitions in a map. These instructions are typically immediate loads
resulting from rematerialization, and address loads emitted by target in
eliminateFrameInde().

This is enabled by default, but a target could easily disable it by means of
'disablePass(&MachineLateInstrsCleanupID);'.

This late cleanup is naturally not "optimal" in removing instructions as it
is done by looking at phys-regs, but still quite effective. It would be
desirable to improve other parts of CodeGen and avoid these redundant
instructions in the first place, but there are no ideas for this yet.

Differential Revision: https://reviews.llvm.org/D123394

Reviewed By: RKSimon, foad, craig.topper, arsenm, asb

Breaks on some apple machines