From a41500a015afe7fec5f7d122a37ccd1031f9fb51 Mon Sep 17 00:00:00 2001
From: Eddie Hung <eddieh@ece.ubc.ca>
Date: Fri, 10 Aug 2018 19:50:27 -0700
Subject: Rework Arch::logicCellsCompatible() to take pointer + size, allowing
 use of std::array

---
 ice40/arch.h        |  2 +-
 ice40/arch_place.cc | 31 ++++++++++++++++---------------
 ice40/chains.cc     |  2 +-
 3 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/ice40/arch.h b/ice40/arch.h
index 561d75c3..1d91a9ae 100644
--- a/ice40/arch.h
+++ b/ice40/arch.h
@@ -802,7 +802,7 @@ struct Arch : BaseCtx
     bool isBelLocationValid(BelId bel) const;
 
     // Helper function for above
-    bool logicCellsCompatible(const std::vector<const CellInfo *> &cells) const;
+    bool logicCellsCompatible(const CellInfo** it, const size_t size) const;
 
     // -------------------------------------------------
     // Assign architecure-specific arguments to nets and cells, which must be
diff --git a/ice40/arch_place.cc b/ice40/arch_place.cc
index 2e2b9556..c69fd34f 100644
--- a/ice40/arch_place.cc
+++ b/ice40/arch_place.cc
@@ -23,15 +23,17 @@
 #include "nextpnr.h"
 #include "util.h"
 
+#include <boost/range/iterator_range.hpp>
+
 NEXTPNR_NAMESPACE_BEGIN
 
-bool Arch::logicCellsCompatible(const std::vector<const CellInfo *> &cells) const
+bool Arch::logicCellsCompatible(const CellInfo** it, const size_t size) const
 {
     bool dffs_exist = false, dffs_neg = false;
     const NetInfo *cen = nullptr, *clk = nullptr, *sr = nullptr;
     int locals_count = 0;
 
-    for (auto cell : cells) {
+    for (auto cell : boost::make_iterator_range(it, it+size)) {
         NPNR_ASSERT(cell->belType == id_ICESTORM_LC);
         if (cell->lcInfo.dffEnable) {
             if (!dffs_exist) {
@@ -71,16 +73,15 @@ bool Arch::logicCellsCompatible(const std::vector<const CellInfo *> &cells) cons
 bool Arch::isBelLocationValid(BelId bel) const
 {
     if (getBelType(bel) == id_ICESTORM_LC) {
-        static std::vector<const CellInfo *> bel_cells;
-        bel_cells.clear();
+        std::array<const CellInfo *, 8> bel_cells;
+        size_t num_cells = 0;
         Loc bel_loc = getBelLocation(bel);
         for (auto bel_other : getBelsByTile(bel_loc.x, bel_loc.y)) {
             CellInfo *ci_other = getBoundBelCell(bel_other);
-            if (ci_other != nullptr) {
-                bel_cells.emplace_back(ci_other);
-            }
+            if (ci_other != nullptr)
+                bel_cells[num_cells++] = ci_other;
         }
-        return logicCellsCompatible(bel_cells);
+        return logicCellsCompatible(bel_cells.data(), num_cells);
     } else {
         CellInfo *ci = getBoundBelCell(bel);
         if (ci == nullptr)
@@ -95,18 +96,18 @@ bool Arch::isValidBelForCell(CellInfo *cell, BelId bel) const
     if (cell->type == id_ICESTORM_LC) {
         NPNR_ASSERT(getBelType(bel) == id_ICESTORM_LC);
 
-        static std::vector<const CellInfo *> bel_cells;
-        bel_cells.clear();
+        std::array<const CellInfo *, 8> bel_cells;
+        size_t num_cells = 0;
+
         Loc bel_loc = getBelLocation(bel);
         for (auto bel_other : getBelsByTile(bel_loc.x, bel_loc.y)) {
             CellInfo *ci_other = getBoundBelCell(bel_other);
-            if (ci_other != nullptr && bel_other != bel) {
-                bel_cells.emplace_back(ci_other);
-            }
+            if (ci_other != nullptr && bel_other != bel)
+                bel_cells[num_cells++] = ci_other;
         }
 
-        bel_cells.emplace_back(cell);
-        return logicCellsCompatible(bel_cells);
+        bel_cells[num_cells++] = cell;
+        return logicCellsCompatible(bel_cells.data(), num_cells);
     } else if (cell->type == id_SB_IO) {
         // Do not allow placement of input SB_IOs on blocks where there a PLL is outputting to.
 
diff --git a/ice40/chains.cc b/ice40/chains.cc
index 8638a96c..bb20b60b 100644
--- a/ice40/chains.cc
+++ b/ice40/chains.cc
@@ -97,7 +97,7 @@ class ChainConstrainer
             }
             tile.push_back(cell);
             chains.back().cells.push_back(cell);
-            bool split_chain = (!ctx->logicCellsCompatible(tile)) || (int(chains.back().cells.size()) > max_length);
+            bool split_chain = (!ctx->logicCellsCompatible(tile.data(), tile.size())) || (int(chains.back().cells.size()) > max_length);
             if (split_chain) {
                 CellInfo *passout = make_carry_pass_out(cell->ports.at(ctx->id("COUT")));
                 tile.pop_back();
-- 
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