tobast/phd-thesis
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

A72 frontend: add example of front-bottleneck

Browse source 
load, fmadd, fmadd, store
This commit is contained in:
Théophile Bastian 2023-09-06 16:55:54 +02:00
parent 277b9e8483
commit 72c289239d
1 changed files with 8 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

9
plan/40_a72_frontend.md
View file

@ -26,7 +26,14 @@
* FP0 * FP0
* FP1 * FP1
* Frontend: 3 insn/cycle * Frontend: 3 insn/cycle
* very limiting compared to its backend (TODO: example?) * very limiting compared to its backend.
* Example: 2nd-order polynomial calculation:
```
P[i] = aX[i]² + bX[i] + c
<=> P[i] = (a*X[i] + b) * X[i] + c
<=> P[i] = (a*X[i] + b); P[i] = P[i] * X[i] + c
```
so load, FMAdd, FMAdd, store. Backend OK, frontend bottleneck.
* Very few hardware counters regarding the frontend! In particular, no access * Very few hardware counters regarding the frontend! In particular, no access
*at all* to macro-ops. No micro-op count. *at all* to macro-ops. No micro-op count.