From 254115c06b0d85610a4ab3cccf0160ffe940676e Mon Sep 17 00:00:00 2001
From: James Cherry <cherry@parallaxsw.com>
Date: Tue, 9 Aug 2022 12:31:33 -0700
Subject: [PATCH] do not merge path delays with -to

Signed-off-by: James Cherry <cherry@parallaxsw.com>
---
 sdc/ExceptionPath.cc | 13 ++++++++++++-
 search/Search.cc     | 23 ++++++++++++++---------
 2 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/sdc/ExceptionPath.cc b/sdc/ExceptionPath.cc
index abc0cc9f..56abfe60 100644
--- a/sdc/ExceptionPath.cc
+++ b/sdc/ExceptionPath.cc
@@ -607,7 +607,18 @@ PathDelay::mergeable(ExceptionPath *exception) const
   return ExceptionPath::mergeable(exception)
     && overrides(exception)
     && exception->ignoreClkLatency() == ignore_clk_latency_
-    && exception->delay() == delay_;
+    && exception->delay() == delay_
+    // path delays -to pin/inst may be along the same path because they
+    // can be internal pins and not restricted to normal endpoints.
+    // This means that
+    //   set_max_delay -to p1
+    //   set_max_delay -to p2
+    // is not the same as
+    //   set_max_delay -to {p1 p2}
+    // when p1 and p2 are on the same path because once endpoint
+    // is encountered the exception is not complete.
+    && to_ == nullptr
+    && exception->to() == nullptr;
 }
 
 bool
diff --git a/search/Search.cc b/search/Search.cc
index 101156c2..a4a13d99 100644
--- a/search/Search.cc
+++ b/search/Search.cc
@@ -2558,10 +2558,7 @@ Search::mutateTag(Tag *from_tag,
 	// Don't propagate a completed false path -thru unless it is a
 	// clock (which ignores exceptions).
 	return nullptr;
-      // Don't propagate path delay tags past the -to pin.
-      if (exception->isPathDelay()
-          && sdc_->isCompleteTo(state, from_pin, from_rf, min_max))
-        return nullptr;
+
       if (state->matchesNextThru(from_pin,to_pin,to_rf,min_max,network_)) {
 	// Found a -thru that we've been waiting for.
 	if (state->nextState()->isComplete()
@@ -2571,8 +2568,13 @@ Search::mutateTag(Tag *from_tag,
 	state_change = true;
 	break;
       }
-      // Kill loop tags at register clock pins.
-      if (to_is_reg_clk && exception->isLoop()) {
+
+      // Kill path delay tags past the -to pin.
+      if ((exception->isPathDelay()
+           && sdc_->isCompleteTo(state, from_pin, from_rf, min_max))
+          // Kill loop tags at register clock pins.
+          || (to_is_reg_clk
+              && exception->isLoop())) {
 	state_change = true;
 	break;
       }
@@ -2607,9 +2609,12 @@ Search::mutateTag(Tag *from_tag,
 	  return nullptr;
 	}
 
-	// Kill loop tags at register clock pins.
-	if (!(to_is_reg_clk
-	      && exception->isLoop()))
+        // Kill path delay tags past the -to pin.
+	if (!((exception->isPathDelay()
+               && sdc_->isCompleteTo(state, from_pin, from_rf, min_max))
+              // Kill loop tags at register clock pins.
+              || (to_is_reg_clk
+                  && exception->isLoop())))
 	  new_states->insert(state);
       }
     }