126.96.36.199. Signal Preservation
The Intel® Quartus® Prime software optimizes the RTL signals during synthesis and place-and-route. RTL signal names may not appear in the post-fit netlist after optimizations.
The optimization attributes are:
- keep—Prevents removal of combinational signals during optimization.
- preserve—Prevents removal of registers during optimization.
However, preserving attributes can increase device resource utilization or decrease timing performance.
Preserving nodes is often necessary when you add groups of signals for an IP with a plug-in. If you are debugging an encrypted IP core, such as the Nios® II CPU, you might need to preserve nodes from the core to keep available for debugging with the Signal Tap Logic Analyzer.
In incremental compilation flows, pre-synthesis nodes may not be connected to the Signal Tap Logic Analyzer for post-fit partitions. Signal Tap issues a critical warning for all pre-synthesis node names that do not exist in the post-fit netlist.
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