[llvm-exegesis] Throughput support in analysis mode

[llvm-exegesis] Throughput support in analysis mode

Summary:
D57000 / [[ https://bugs.llvm.org/show_bug.cgi?id=37698 | PR37698 ]] added support for measuring of the inverse throughput.
But the support for the analysis was not added.
This attempts to fix that. (analysis done o bdver2 / piledriver)

First, small-scale experiment:
```
$ ./bin/llvm-exegesis -num-repetitions=10000 -mode=inverse_throughput -opcode-name=BSF64rr
Check generated assembly with: /usr/bin/objdump -d /tmp/snippet-d0acdd.o
---
mode:            inverse_throughput
key:
  instructions:
    - 'BSF64rr RAX RDX'
  config:          ''
  register_initial_values:
    - 'RDX=0x0'
cpu_name:        bdver2
llvm_triple:     x86_64-unknown-linux-gnu
num_repetitions: 10000
measurements:
  - { key: inverse_throughput, value: 3.0278, per_snippet_value: 3.0278 }
error:           ''
info:            instruction has no tied variables picking Uses different from defs
assembled_snippet: 48BA0000000000000000480FBCC2480FBCC2480FBCC2480FBCC2480FBCC2480FBCC2480FBCC2480FBCC2480FBCC2480FBCC2480FBCC2480FBCC2480FBCC2480FBCC2480FBCC2480FBCC2C3
...
```
If we plug `bsfq	%r12, %r10` into llvm-mca:
https://godbolt.org/z/ZtOyhJ
```
Dispatch Width:    4
uOps Per Cycle:    3.00
IPC:               0.50
Block RThroughput: 2.0
```
So RThroughput mismatch exists.

Now, let's upscale and analyse:
{F8207148}
`$ ./bin/llvm-exegesis -mode=analysis -analysis-epsilon=1.0 -benchmarks-file=/tmp/benchmarks-inverse_throughput.yaml -analysis-inconsistencies-output-file=/tmp/clusters.html`:
{F8207172}
{F8207197}
And if we now look at https://www.agner.org/optimize/instruction_tables.pdf,
`Reciprocal throughput` for `BSF r,r` is listed as `3`.
Yay?

Reviewers: courbet, gchatelet

Reviewed By: courbet

Subscribers: tschuett, RKSimon, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D57647

llvm-svn: 353023