From fffc63970de97298454dcd0eb3fa451753a23399 Mon Sep 17 00:00:00 2001
From: Geza Lore <gezalore@gmail.com>
Date: Wed, 18 Aug 2021 10:54:45 +0100
Subject: [PATCH] Use narrowest RedXor

---
 src/V3Cast.cpp    | 7 ++++---
 src/V3EmitCFunc.h | 7 ++++++-
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/V3Cast.cpp b/src/V3Cast.cpp
index 0406149c8..de912c72e 100644
--- a/src/V3Cast.cpp
+++ b/src/V3Cast.cpp
@@ -155,9 +155,10 @@ private:
         }
     }
     virtual void visit(AstVarRef* nodep) override {
-        if (nodep->access().isReadOnly() && !VN_IS(nodep->backp(), CCast)
-            && VN_IS(nodep->backp(), NodeMath) && !VN_IS(nodep->backp(), ArraySel)
-            && nodep->backp()->width() && castSize(nodep) != castSize(nodep->varp())) {
+        AstNode* const backp = nodep->backp();
+        if (nodep->access().isReadOnly() && !VN_IS(backp, CCast) && VN_IS(backp, NodeMath)
+            && !VN_IS(backp, ArraySel) && !VN_IS(backp, RedXor) && backp->width()
+            && castSize(nodep) != castSize(nodep->varp())) {
             // Cast vars to IData first, else below has upper bits wrongly set
             //  CData x=3; out = (QData)(x<<30);
             insertCast(nodep, castSize(nodep));
diff --git a/src/V3EmitCFunc.h b/src/V3EmitCFunc.h
index 03c2b30b7..144307b88 100644
--- a/src/V3EmitCFunc.h
+++ b/src/V3EmitCFunc.h
@@ -975,8 +975,13 @@ public:
         if (nodep->lhsp()->isWide()) {
             visit(VN_CAST(nodep, NodeUniop));
         } else {
+            AstVarRef* const vrefp = VN_CAST(nodep->lhsp(), VarRef);
+            const int widthPow2 = vrefp ? vrefp->varp()->dtypep()->widthPow2()
+                                        : nodep->lhsp()->dtypep()->widthPow2();
+            UASSERT_OBJ(widthPow2 > 1, nodep,
+                        "Reduction over single bit value should have been folded");
             putbs("VL_REDXOR_");
-            puts(cvtToStr(nodep->lhsp()->dtypep()->widthPow2()));
+            puts(cvtToStr(widthPow2));
             puts("(");
             iterateAndNextNull(nodep->lhsp());
             puts(")");