dfflegalize: Fix decision tree for adffe.

When an adffe is being legalized, and is not natively supported,
prioritize unmapping to adff over converting to dffsre if dffsre is not
natively supported itself.

Fixes #2361.

diff --git a/passes/techmap/dfflegalize.cc b/passes/techmap/dfflegalize.cc
index 8ad65493f0fe37ef299d9e6f41652d47b2ab7e57..c1e7e557d927a8f61a5fd586e90bcebc7fd4b98b 100644 (file)
--- a/passes/techmap/dfflegalize.cc
+++ b/passes/techmap/dfflegalize.cc
@@ -418,7 +418,8 @@ unmap_enable:
                                        ff_type = has_set ? FF_ADFFE1 : FF_ADFFE0;
                                        break;
                                }
-                               if (supported_dffsr & initmask) {
+                               if (supported_cells[has_en ? FF_DFFSRE : FF_DFFSR] & initmask) {
+adff_to_dffsr:
                                        // Throw in a set/reset, retry in DFFSR/DFFSRE branch.
                                        if (has_set) {
                                                sig_s = sig_r;
@@ -441,6 +442,9 @@ unmap_enable:
                                        ff_type = has_set ? FF_ADFF1 : FF_ADFF0;
                                        goto unmap_enable;
                                }
+                               if (supported_dffsr & initmask) {
+                                       goto adff_to_dffsr;
+                               }
                                log_assert(!((has_set ? supported_adff1 : supported_adff0) & initmask));
                                // Alright, so this particular combination of initval and
                                // resetval is not natively supported.  First, try flipping