From e7d63c76443dcf84cf67cd5884064228b70180b7 Mon Sep 17 00:00:00 2001
From: Wilson Snyder <wsnyder@wsnyder.org>
Date: Mon, 8 Oct 2012 07:05:54 -0400
Subject: [PATCH] Fix large shift error on large shift constants.

---
 Changes                       |  2 ++
 src/V3Width.cpp               | 16 +++++++++++++---
 test_regress/t/t_math_shift.v |  2 ++
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/Changes b/Changes
index deb9a126d..86cfdcfa9 100644
--- a/Changes
+++ b/Changes
@@ -7,6 +7,8 @@ indicates the contributor was also the author of the fix; Thanks!
 
 ****  Fix parameter pins interspersed with cells broke in 3.840.  [Bernard Deadman]
 
+****  Fix large shift error on large shift constants.  [David Welch]
+
 
 * Verilator 3.841 2012/09/03
 
diff --git a/src/V3Width.cpp b/src/V3Width.cpp
index 8e76277ef..ca39ebbb5 100644
--- a/src/V3Width.cpp
+++ b/src/V3Width.cpp
@@ -1821,9 +1821,19 @@ private:
 	    int width=nodep->width();  int ewidth=nodep->widthMin();
 	    nodep->lhsp()->iterateAndNext(*this,WidthVP(width,ewidth,FINAL).p());
 	    widthCheck(nodep,"LHS",nodep->lhsp(),width,ewidth);
-	    if (nodep->rhsp()->width()>32)
-		nodep->rhsp()->v3error("Unsupported: Shifting of by over 32-bit number isn't supported."
-				       <<" (This isn't a shift of 32 bits, but a shift of 2^32, or 4 billion!)\n");
+	    if (nodep->rhsp()->width()>32) {
+		AstConst* shiftp = nodep->rhsp()->castConst();
+		if (shiftp && shiftp->num().mostSetBitP1() <= 32) {
+		    // If (number)<<96'h1, then make it into (number)<<32'h1
+		    V3Number num (shiftp->fileline(), 32, 0); num.opAssign(shiftp->num());
+		    AstNode* shiftp = nodep->rhsp();
+		    nodep->rhsp()->replaceWith(new AstConst(shiftp->fileline(), num));
+		    shiftp->deleteTree(); shiftp=NULL;
+		} else {
+		    nodep->rhsp()->v3error("Unsupported: Shifting of by over 32-bit number isn't supported."
+					   <<" (This isn't a shift of 32 bits, but a shift of 2^32, or 4 billion!)\n");
+		}
+	    }
 	}
 	return nodep;  // May edit
     }
diff --git a/test_regress/t/t_math_shift.v b/test_regress/t/t_math_shift.v
index 3069a3d40..796c7403b 100644
--- a/test_regress/t/t_math_shift.v
+++ b/test_regress/t/t_math_shift.v
@@ -40,6 +40,8 @@ module t (/*AUTOARG*/
 	    if (5'sb10110>>>2 != 5'sb11101) $stop;
 	    if (5'sb10110<<2  != 5'sb11000) $stop;
 	    if (5'sb10110<<<2 != 5'sb11000) $stop;
+	    // Allow >64 bit shifts if the shift amount is a constant
+	    if ((64'sh458c2de282e30f8b >> 68'sh4) !== 64'sh0458c2de282e30f8) $stop;
 	 end
 	 if (cyc==2) begin
 	    amt <= 32'd28;