Internal: Add C++20ish reverse_view for range loops. No functional change (#3388).

Signed-off-by: HungMingWu <u9089000@gmail.com>

include/verilated_types.h

@@ -410,16 +410,16 @@ public:
     }
     template <typename Func> VlQueue find_last(Func with_func) const {
         IData index = m_deque.size() - 1;
-        for (auto it = m_deque.rbegin(); it != m_deque.rend(); ++it) {
+        for (auto& item : vlstd::reverse_view(m_deque)) {
-            if (with_func(index, *it)) return VlQueue::cons(*it);
+            if (with_func(index, item)) return VlQueue::cons(item);
             --index;
         }
         return VlQueue{};
     }
     template <typename Func> VlQueue<IData> find_last_index(Func with_func) const {
         IData index = m_deque.size() - 1;
-        for (auto it = m_deque.rbegin(); it != m_deque.rend(); ++it) {
+        for (auto& item : vlstd::reverse_view(m_deque)) {
-            if (with_func(index, *it)) return VlQueue<IData>::cons(index);
+            if (with_func(index, item)) return VlQueue<IData>::cons(index);
             --index;
         }
         return VlQueue<IData>{};

include/verilatedos.h

@@ -521,6 +521,19 @@ using ssize_t = uint32_t;  ///< signed size_t; returned from read()
 // Conversions
 
 namespace vlstd {
+
+template <typename T> struct reverse_wrapper {
+    const T& m_v;
+
+    explicit reverse_wrapper(const T& a_v)
+        : m_v(a_v) {}
+    inline auto begin() -> decltype(m_v.rbegin()) { return m_v.rbegin(); }
+    inline auto end() -> decltype(m_v.rend()) { return m_v.rend(); }
+};
+
+// C++20's std::ranges::reverse_view
+template <typename T> reverse_wrapper<T> reverse_view(const T& v) { return reverse_wrapper<T>(v); }
+
 // C++17's std::as_const
 template <class T> T const& as_const(T& v) { return v; }
 };  // namespace vlstd

src/V3EmitMk.cpp

@@ -333,8 +333,8 @@ class EmitMkHierVerilation final {
         const V3HierBlockPlan::HierVector blocks
             = m_planp->hierBlocksSorted();  // leaf comes first
         // List in order of leaf-last order so that linker can resolve dependency
-        for (auto it = blocks.rbegin(); it != blocks.rend(); ++it) {
+        for (auto& block : vlstd::reverse_view(blocks)) {
-            of.puts("\t" + (*it)->hierLib(true) + " \\\n");
+            of.puts("\t" + block->hierLib(true) + " \\\n");
         }
         of.puts("\n");
 

src/V3Inline.cpp

@@ -190,8 +190,7 @@ private:
 
         // Iterate through all modules in bottom-up order.
         // Make a final inlining decision for each.
-        for (auto it = m_allMods.rbegin(); it != m_allMods.rend(); ++it) {
+        for (AstNodeModule* const modp : vlstd::reverse_view(m_allMods)) {
-            AstNodeModule* const modp = *it;
 
             // If we're going to inline some modules into this one,
             // update user4 (statement count) to reflect that:

src/V3LinkJump.cpp

@@ -263,10 +263,10 @@ private:
         UINFO(8, "   DISABLE " << nodep << endl);
         iterateChildren(nodep);
         AstNodeBlock* blockp = nullptr;
-        for (auto it = m_blockStack.rbegin(); it != m_blockStack.rend(); ++it) {
+        for (AstNodeBlock* const stackp : vlstd::reverse_view(m_blockStack)) {
-            UINFO(9, "    UNDERBLK  " << *it << endl);
+            UINFO(9, "    UNDERBLK  " << stackp << endl);
-            if ((*it)->name() == nodep->name()) {
+            if (stackp->name() == nodep->name()) {
-                blockp = *it;
+                blockp = stackp;
                 break;
             }
         }

src/V3ParseSym.h

@@ -128,8 +128,7 @@ public:
     }
     void showUpward() {  // LCOV_EXCL_START
         UINFO(1, "ParseSym Stack:\n");
-        for (auto it = m_sympStack.rbegin(); it != m_sympStack.rend(); ++it) {
+        for (VSymEnt* const symp : vlstd::reverse_view(m_sympStack)) {
-            VSymEnt* const symp = *it;
             UINFO(1, "    " << symp->nodep() << endl);
         }
         UINFO(1, "ParseSym Current: " << symCurrentp()->nodep() << endl);

src/V3Partition.cpp

@@ -526,9 +526,9 @@ public:
     }
     void checkRelativesCp(GraphWay way) const {
         const EdgeSet& edges = m_edges[way];
-        for (EdgeSet::const_reverse_iterator it = edges.rbegin(); it != edges.rend(); ++it) {
+        for (const auto& edge : vlstd::reverse_view(edges)) {
-            const LogicMTask* const relativep = (*it).key();
+            const LogicMTask* const relativep = edge.key();
-            const uint32_t cachedCp = (*it).value();
+            const uint32_t cachedCp = edge.value();
             partCheckCachedScoreVsActual(cachedCp, relativep->critPathCost(way.invert())
                                                        + relativep->stepCost());
         }
@@ -555,12 +555,12 @@ public:
         // wayEdgeEndp(way, withoutp). This should take 2 iterations max.
         const EdgeSet& edges = m_edges[way.invert()];
         uint32_t result = 0;
-        for (EdgeSet::const_reverse_iterator it = edges.rbegin(); it != edges.rend(); ++it) {
+        for (const auto& edge : vlstd::reverse_view(edges)) {
-            if ((*it).key() != withoutp->furtherp(way.invert())) {
+            if (edge.key() != withoutp->furtherp(way.invert())) {
                 // Use the cached cost. It could be a small overestimate
                 // due to stepping. This is consistent with critPathCost()
                 // which also returns the cached cost.
-                result = (*it).value();
+                result = edge.value();
                 break;
             }
         }

src/V3Simulate.h

@@ -182,11 +182,11 @@ public:
             }
             m_whyNotOptimizable = why;
             std::ostringstream stack;
-            for (auto it = m_callStack.rbegin(); it != m_callStack.rend(); ++it) {
+            for (auto& callstack : vlstd::reverse_view(m_callStack)) {
-                AstFuncRef* const funcp = (*it)->m_funcp;
+                AstFuncRef* const funcp = callstack->m_funcp;
                 stack << "\n        " << funcp->fileline() << "... Called from "
                       << funcp->prettyName() << "() with parameters:";
-                V3TaskConnects* tconnects = (*it)->m_tconnects;
+                V3TaskConnects* tconnects = callstack->m_tconnects;
                 for (V3TaskConnects::iterator conIt = tconnects->begin();
                      conIt != tconnects->end(); ++conIt) {
                     AstVar* const portp = conIt->first;