In the modern deep-submicron Very Large Integrated Circuit(VLSI) design flow intercon-
nect delays are becoming major limiting factor for timing closure. Traditional placement
algorithms such as routability-driven placement (improves routability) and wirelength-
driven placement (reduces total wirelength) are no longer sufficient to close timing. To
this end, timing-driven placement plays a crucial role in reducing the interconnect delay
through timing critical paths (paths with timing violations/negative slacks) of the design
and thereby achieving specific performance/clock frequency.
In the placement flow, timing information about the design can be incorporated during
global placement and/or incremental/detailed placement. Although, over the years, there
has been significant advances in the quality of the global placement, there is a growing need
for high performance incremental timing-driven placement due to the lack of accurate
interconnect information during global placement. Moreover, incremental timing-driven
placement is essential to recover timing while preserving the other optimization objectives
such as total wirelength, routing congestion, and so forth which are optimized at the early
stages of the design flow.
This thesis proposes a simple, yet efficient, incremental timing-driven placement algo-
rithm that seeks to find optimized locations for standard cells so that the total negative
slack of the design can be maximized. Our algorithm consists two stages: (1) Global Move
which positions standard cells inside a critical bounding box to eliminate timing violations
on timing critical nets; and (2) Local Move which provides further timing improvement by
finely adjusting the current locations of the standard cells within a local region.
We evaluate our algorithm using ICCAD-2014 timing-driven placement contest bench-
marks. The results show that, on average, our technique eliminates 94% and 30% of the
late and early total negative slacks, respectively, and, 82% and 27% of the late and early
worst negative slacks, respectively, under short and long displacement constraints. The
1st-place team of the contest improves late and early total negative slacks by 90% and
39%, respectively, and improves late and early worst negative slack by 76% and 32%, re-
spectively. Taking into account both timing violation improvement and the placement
quality (i.e., other objectives), on average, we outperform the 1st-place team by 3% in
terms of the ICCAD-2014 contest quality score and our technique is 4.6× faster in terms
of runtime