From d20a4db7738fe7f5c7e0b1df7231a45215f04ce8 Mon Sep 17 00:00:00 2001
From: Geza Lore <gezalore@gmail.com>
Date: Mon, 18 May 2020 18:46:00 +0100
Subject: [PATCH] Fix regression due to early constant folding in +: and -:
 (#2338)

---
 src/V3WidthSel.cpp             |  1 +
 test_regress/t/t_select_plus.v | 15 +++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/src/V3WidthSel.cpp b/src/V3WidthSel.cpp
index c23f0c208..8e539443e 100644
--- a/src/V3WidthSel.cpp
+++ b/src/V3WidthSel.cpp
@@ -458,6 +458,7 @@ private:
         UINFO(6, "SELPLUS/MINUS " << nodep << endl);
         // Below 2 lines may change nodep->widthp()
         if (debug() >= 9) nodep->dumpTree(cout, "--SELPM0: ");
+        V3Width::widthParamsEdit(nodep->rhsp());  // constifyEdit doesn't ensure widths finished
         V3Const::constifyEdit(nodep->rhsp());  // May relink pointed to node, ok if not const
         V3Const::constifyParamsEdit(nodep->thsp());  // May relink pointed to node
         checkConstantOrReplace(nodep->thsp(), "Width of :+ or :- bit extract isn't a constant");
diff --git a/test_regress/t/t_select_plus.v b/test_regress/t/t_select_plus.v
index 9d9e55879..247f166f8 100644
--- a/test_regress/t/t_select_plus.v
+++ b/test_regress/t/t_select_plus.v
@@ -74,4 +74,19 @@ module t (/*AUTOARG*/
       endcase
    end
 
+   // Additional constant folding check - this used to trigger a bug
+   reg [23:0] a;
+   reg [3:0]  b;
+
+   initial begin
+     a = 24'd0;
+     b = 4'b0111;
+     a[3*(b[2:0]+0)+:3] = 3'd7; // Check LSB expression goes to 32-bits
+     if (a != 24'b11100000_00000000_00000000) $stop;
+
+     a = 24'd0;
+     b = 4'b0110;
+     a[3*(b[2:0]+0)-:3] = 3'd7; // Check MSB expression goes to 32-bits
+     if (a != 24'b00000111_00000000_00000000) $stop;
+   end
 endmodule