From 42d2cdc119e2c1b33883f0aad4877e54f2791e6a Mon Sep 17 00:00:00 2001
From: Alex Wilson <alex.david.wilson@gmail.com>
Date: Thu, 29 May 2025 22:24:50 -0600
Subject: [PATCH] Merge dists when combining randsets

When two randsets with dist constraints combined the dists from the
current randset were getting lost. This meant that for two related
variables with dists that only the last dist was ever used in the
randomization/swizzler.

This adds or merges the dist_field_m dict entries to the existing
randset to retain them.

Added a test case that ties two variables together with an enable bit
conditional.
---
 src/vsc/model/rand_info_builder.py |  6 +++++
 ve/unit/test_constraint_dist.py    | 37 ++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/src/vsc/model/rand_info_builder.py b/src/vsc/model/rand_info_builder.py
index b7beac7..b2fa433 100644
--- a/src/vsc/model/rand_info_builder.py
+++ b/src/vsc/model/rand_info_builder.py
@@ -390,6 +390,12 @@ def process_fieldref(self, fm):
                     self._randset_field_m[f] = ex_randset
                     ex_randset.add_field(f)
 
+                for f, s in self._active_randset.dist_field_m.items():
+                    if f in ex_randset.dist_field_m.keys():
+                        ex_randset.dist_field_m[f].extend(s)
+                    else:
+                        ex_randset.dist_field_m[f] = s
+
                 for c in self._active_randset.constraints():
                     ex_randset.add_constraint(c)
                     
diff --git a/ve/unit/test_constraint_dist.py b/ve/unit/test_constraint_dist.py
index 2391b49..6d4970c 100644
--- a/ve/unit/test_constraint_dist.py
+++ b/ve/unit/test_constraint_dist.py
@@ -254,6 +254,43 @@ def dist_a(self):
                 self.fail("Value " + str(c.a) + " illegal")
         print("hist: " + str(hist))
 
+    def test_dist_multiple_dists_in_randset(self):
+
+        @vsc.randobj
+        class my_c(object):
+
+            def __init__(self):
+                self.a = vsc.rand_bit_t()
+                self.b = vsc.rand_bit_t()
+                self.en = vsc.rand_bit_t()
+
+            @vsc.constraint
+            def multi_dists(self):
+                vsc.dist(self.a, [
+                    vsc.weight(0, 1),
+                    vsc.weight(1, 99999)])
+                vsc.dist(self.b, [
+                    vsc.weight(0, 1),
+                    vsc.weight(1, 99999)])
+                with vsc.implies(self.en == 0):
+                    self.a == 0
+                    self.b == 0
+
+        c = my_c()
+
+        hist = 2*[0]
+
+        for i in range(100):
+            with c.randomize_with() as it:
+                it.en == 1
+            hist[0] += c.a
+            hist[1] += c.b
+
+        print("hist: " + str(hist))
+        for h in hist:
+            self.assertGreater(h, 95)
+
+
     def test_dist_array_elems(self):
 
         @vsc.randobj