Fix errant integer promotion (#7012)

src/V3Clean.cpp

@@ -18,7 +18,7 @@
 // Each module:
 //      For each expression, if it requires a clean operand,
 //      and the operand is dirty, insert a CLEAN node.
-//      Resize operands to C++ 32/64/wide types.
+//      Resize operands (but not variables or variable selects) to C++ 32/64/wide types.
 //      Copy all width() values to widthMin() so RANGE, etc can still see orig widths
 //
 //*************************************************************************
@@ -83,6 +83,7 @@ class CleanVisitor final : public VNVisitor {
             if (VN_IS(nodep, Var)  //
                 || VN_IS(nodep, ConsPackMember)  //
                 || VN_IS(nodep, NodeDType)  // Don't want to change variable widths!
+                || VN_IS(nodep, NodeSel)  // Array selects should reflect variable widths
                 || VN_IS(nodep->dtypep()->skipRefp(), AssocArrayDType)  // Or arrays
                 || VN_IS(nodep->dtypep()->skipRefp(), WildcardArrayDType)
                 || VN_IS(nodep->dtypep()->skipRefp(), DynArrayDType)

src/Verilator.cpp

@@ -527,7 +527,8 @@ static void process() {
             // Bits between widthMin() and width() are irrelevant, but may be non zero.
             v3Global.widthMinUsage(VWidthMinUsage::VERILOG_WIDTH);
 
-            // Make all expressions either 8, 16, 32 or 64 bits
+            // Make all expressions 32, 64, or 32*N bits
+            // Variables and selects-of-variables remain verilog-width
             V3Clean::cleanAll(v3Global.rootp());
 
             // Move wide constants to BLOCK temps / ConstPool.