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authorEddie Hung <eddie@fpgeh.com>2019-06-10 10:32:19 -0700
committerEddie Hung <eddie@fpgeh.com>2019-06-10 10:32:19 -0700
commit5b999ae68decef5646ef0ccac53463f22fe18d8f (patch)
treeb9709201eb81fa786fb6ef82f0ff84beea97e4b1 /passes/opt
parent1dd7e23a20bcbfdf69f34d5060637da49fce7b46 (diff)
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Elaborate muxpack doc
Diffstat (limited to 'passes/opt')
-rw-r--r--passes/opt/muxpack.cc8
1 files changed, 6 insertions, 2 deletions
diff --git a/passes/opt/muxpack.cc b/passes/opt/muxpack.cc
index f01d5474d..b6f3313bf 100644
--- a/passes/opt/muxpack.cc
+++ b/passes/opt/muxpack.cc
@@ -302,8 +302,12 @@ struct MuxpackPass : public Pass {
log(" muxpack [selection]\n");
log("\n");
log("This pass converts cascaded chains of $pmux cells (e.g. those create from case\n");
- log("constructs) and $mux cells (e.g. those created by if-else constructs) into \n");
- log("into $pmux cells.\n");
+ log("constructs) and $mux cells (e.g. those created by if-else constructs) into\n");
+ log("$pmux cells.\n");
+ log("\n");
+ log("This optimisation is conservative --- it will only pack $mux or $pmux cells with\n");
+ log("other such cells if it can be certain that the select lines are mutually\n");
+ log("exclusive.\n");
log("\n");
}
void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE