Commercial tools

Without access to source codes of commercial tools, we could not incorporate interconnect-awareness into them as we did to SCALP. Moreover, most commercially available tools do not take directives from RTL floorplanners to lay out a circuit. Therefore, physical locality we try to maximize at RTL may be easily destroyed when commercial tools put an IAPO RTL circuit through logic and physical synthesis. Nevertheless, we were interested in whether a RTL circuit synthesized using our techniques would be any different if it was handed out to commercial tools for logic and physical synthesis. We employed Synopsys Design Compiler to synthesize both IUPO and IAPO RTL circuits, and employed Cadence Silicon Ensemble for physical synthesis. A standard cell library for TSMC 0.25$\mu$m process developed by the VTVT group in Virginia Tech. was used. Table IV shows the number of semi-global and global wires (wires longer than 1$\mu$m) in the benchmarks synthesized by commercial tools. Surprisingly, 7 of the 8 benchmarks demonstrate fewer such wires for IAPO designs. Although these commercial tools may destroy the circuit hierarchy and do not take any floorplan hints from the RTL design, our techniques are powerful enough to have positive impact in most of the benchmarks. That is, a design with a better RTL interconnect topology turns out to have a better interconnect topology after final routing. (For the benchmark $WDF$, the negative impact may be contributed to its big area overhead of IAPO over IUPO, which may overwhelm the interconnect topology improvement when going through the RTL-hint-free commercial tools.) As many commercial tools are going to take RTL directives for logic and physical synthesis, we expect our techniques to be more beneficial when working with commercial tools.

Table IV: Number of semi-global and global wires in commercial-tool synthesized IAPO and IUPO designs.

	Chemical	DCT_IJPEG	DCT_Wang	Diffeq	Elliptic	IIR77	Jacobi	WDF
IAPO	8720	15298	13037	2872	11520	13919	11264	7682
IUPO	8770	17419	13999	2942	11726	18499	11584	6406