ResourceUsage is a very sparse table. On large input asm sequences it
consumes a lot of memory utilizing only a few percents of it (~4% on my
benchmark). Reorganization of ResourceUsage to keep only used fields
allows saving up to 18% of total memory use by mca or ~850% of input
file size (~1.1GB in absolute values in my case).

D150312 added a TODO:

TODO: consider renaming the field `StartAtCycle` and `Cycles` to
`AcquireAtCycle` and `ReleaseAtCycle` respectively, to stress the
fact that resource allocation is now represented as an interval,
relatively to the issue cycle of the instruction.

This patch implements that TODO. This naming clarifies how to use these
fields in the scheduler. In addition it was confusing that `StartAtCycle` was
singular but `Cycles` was plural. This renaming fixes this inconsistency.

This commit as previously reverted since it missed renaming that came
down after rebasing. This version of the commit fixes those problems.

Differential Revision: https://reviews.llvm.org/D158568

This reverts commit 5b854f2c23ea1b000cb4cac4c0fea77326c03d43.

Build still failing.

D150312 added a TODO:

TODO: consider renaming the field `StartAtCycle` and `Cycles` to
`AcquireAtCycle` and `ReleaseAtCycle` respectively, to stress the
fact that resource allocation is now represented as an interval,
relatively to the issue cycle of the instruction.

This patch implements that TODO. This naming clarifies how to use these
fields in the scheduler. In addition it was confusing that `StartAtCycle` was
singular but `Cycles` was plural. This renaming fixes this inconsistency.

This commit as previously reverted since it missed renaming that came
down after rebasing. This version of the commit fixes those problems.

Differential Revision: https://reviews.llvm.org/D158568

This reverts commit 030d33409568b2f0ea61116e83fd40ca27ba33ac.

This commit is causing build failures

D150312 added a TODO:

TODO: consider renaming the field `StartAtCycle` and `Cycles` to
`AcquireAtCycle` and `ReleaseAtCycle` respectively, to stress the
fact that resource allocation is now represented as an interval,
relatively to the issue cycle of the instruction.

This patch implements that TODO. This naming clarifies how to use these
fields in the scheduler. In addition it was confusing that `StartAtCycle` was
singular but `Cycles` was plural. This renaming fixes this inconsistency.

Differential Revision: https://reviews.llvm.org/D158568

implemented at this time are Summary, Timeline, ResourcePressure and InstructionInfo.
Use --json on the command line to obtain JSON output.

including printing them.

Reviewers: andreadb, lebedev.ri

Differential Review: https://reviews.llvm.org/D86390

Introduces a new base class "InstructionView" that such views derive from.
Other views still use the "View" base class.