If no command arguments (other than -incremental) are specified, the tool reuses as
much of the reference checkpoint information that it can. However, command arguments
can be applied to the read_checkpoint -incremental command that
give the user control over what is used and not reused.
-auto_incremental Option
This enables the automatic incremental flow described in Automatic Incremental.
-reuse_objects Option
-reuse_objects <cell objects>The -reuse_objects can take either cells, clock regions or SLRs as
an argument. When specifying cells, use the get_cells command. When
using get_cells, hierarchical or leaf cells can be specified along with cell types
when using the -filter switch. When specifying clock regions (get_clock_regions) or
SLRs (get_slrs) for reuse, the cells in the region of the reference checkpoint will
be reused if they exist in the incremental run. When specifying any of the
arguments, net reuse is inferred based on the cells identified for reuse.
-fix_objects Option
-fix_objects <cell objects>The -fix_objects option can be used to lock a subset of cells. These
cells are not touched by the incremental place and route tools. The
-fix_objects option only works on cells that match and are
identified for cell reuse. This is the full design space when
-reuse_objects is not specified, or the associated cells when
-reuse_objects is specified.
Examples
The following are examples of their use:
- To reuse and fix only Block Memory
placement:
read_checkpoint -incremental routed.dcp -reuse_objects [all_rams] -fix_objects [all_rams] - To reuse and fix only DSP
placement:
read_checkpoint -incremental routed.dcp -reuse_objects [all_dsps] -fix_objects [all_dsps] - To reuse both Block Memory and DSP placement, and fix the placement of all
cells specified for
reuse:
read_checkpoint -incremental routed.dcp -reuse_objects [all_rams] \ -reuse_objects [all_dsps] -fix_objects [current_design] - To reuse all cells at and below the level of hierarchy indicated and allow the
tools some flexibility to deal with changes in critical
areas:
read_checkpoint -incremental routed.dcp \ -reuse_objects [get_cells <cell_name>] -fix_objects [get_cells <cell_name>]