TargetSchedule.td explicitly allows the usage of a ProcResource for zero
cycles, in order to represent that the ProcResource must be available
but is not consumed by the instruction. On the other hand,
ResourceSegments explicitly does not allow for a zero sized interval. In
order to remedy this, this patch handles the special case of when there
is an empty interval usage of a resource by not adding an empty
interval.
We ran into this issue downstream, but it makes sense to have
this upstream since it is explicitly allowed by TargetSchedule.td.
Re-landing the code that was reverted because of the buildbot failure
in https://lab.llvm.org/buildbot#builders/9/builds/27319.
Original commit message
======================
The class `ResourceSegments` is used to keep track of the intervals
that represent resource usage of a list of instructions that are
being scheduled by the machine scheduler.
The collection is made of intervals that are closed on the left and
open on the right (represented by the standard notation `[a, b)`).
These collections of intervals can be extended by `add`ing new
intervals accordingly while scheduling a basic block.
Unit tests are added to verify the possible configurations of
intervals, and the relative possibility of scheduling a new
instruction in these configurations. Specifically, the methods
`getFirstAvailableAtFromBottom` and `getFirstAvailableAtFromTop` are
tested to make sure that both bottom-up and top-down scheduling work
when tracking resource usage across the basic block with
`ResourceSegments`.
Note that the scheduler tracks resource usage with two methods:
1. counters (via `std::vector<unsigned> ReservedCycles;`);
2. intervals (via `std::map<unsigned, ResourceSegments> ReservedResourceSegments;`).
This patch can be considered a NFC test for existing scheduling models
because the tracking system that uses intervals is turned off by
default (field `bit EnableIntervals = false;` in the tablegen class
`SchedMachineModel`).
Reviewed By: andreadb
Differential Revision: https://reviews.llvm.org/D150312
Reverted because it produces the following builbot failure at https://lab.llvm.org/buildbot#builders/9/builds/27319:
/b/ml-opt-rel-x86-64-b1/llvm-project/llvm/unittests/CodeGen/SchedBoundary.cpp: In member function ‘virtual void ResourceSegments_getFirstAvailableAtFromBottom_empty_Test::TestBody()’:
/b/ml-opt-rel-x86-64-b1/llvm-project/llvm/unittests/CodeGen/SchedBoundary.cpp:395:31: error: call of overloaded ‘ResourceSegments(<brace-enclosed initializer list>)’ is ambiguous
395 | auto X = ResourceSegments({});
| ^
This reverts commit dc312f0331309692e8d6e06e93b3492b6a40989f.
The class `ResourceSegments` is used to keep track of the intervals
that represent resource usage of a list of instructions that are
being scheduled by the machine scheduler.
The collection is made of intervals that are closed on the left and
open on the right (represented by the standard notation `[a, b)`).
These collections of intervals can be extended by `add`ing new
intervals accordingly while scheduling a basic block.
Unit tests are added to verify the possible configurations of
intervals, and the relative possibility of scheduling a new
instruction in these configurations. Specifically, the methods
`getFirstAvailableAtFromBottom` and `getFirstAvailableAtFromTop` are
tested to make sure that both bottom-up and top-down scheduling work
when tracking resource usage across the basic block with
`ResourceSegments`.
Note that the scheduler tracks resource usage with two methods:
1. counters (via `std::vector<unsigned> ReservedCycles;`);
2. intervals (via `std::map<unsigned, ResourceSegments> ReservedResourceSegments;`).
This patch can be considered a NFC test for existing scheduling models
because the tracking system that uses intervals is turned off by
default (field `bit EnableIntervals = false;` in the tablegen class
`SchedMachineModel`).
Reviewed By: andreadb
Differential Revision: https://reviews.llvm.org/D150312
