From 458aa20161504c06dbfc282be3dd7717a575a31e Mon Sep 17 00:00:00 2001
From: David Shah <dave@ds0.me>
Date: Fri, 16 Nov 2018 17:36:34 +0000
Subject: [PATCH] ecp5: More optimal LUT6 placement

Signed-off-by: David Shah <dave@ds0.me>
---
 ecp5/arch_place.cc | 6 ++++++
 ecp5/archdefs.h    | 1 +
 ecp5/pack.cc       | 5 ++++-
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/ecp5/arch_place.cc b/ecp5/arch_place.cc
index 41f87cb8..ff70bb5a 100644
--- a/ecp5/arch_place.cc
+++ b/ecp5/arch_place.cc
@@ -75,6 +75,8 @@ bool Arch::isBelLocationValid(BelId bel) const
                 bel_cells.push_back(cell_other);
             }
         }
+        if (getBoundBelCell(bel) != nullptr && getBoundBelCell(bel)->sliceInfo.has_l6mux && ((bel_loc.z % 2) == 1))
+            return false;
         return slicesCompatible(bel_cells);
     } else {
         CellInfo *cell = getBoundBelCell(bel);
@@ -92,6 +94,10 @@ bool Arch::isValidBelForCell(CellInfo *cell, BelId bel) const
 
         std::vector<const CellInfo *> bel_cells;
         Loc bel_loc = getBelLocation(bel);
+
+        if (cell->sliceInfo.has_l6mux && ((bel_loc.z % 2) == 1))
+            return false;
+
         for (auto bel_other : getBelsByTile(bel_loc.x, bel_loc.y)) {
             CellInfo *cell_other = getBoundBelCell(bel_other);
             if (cell_other != nullptr && bel_other != bel) {
diff --git a/ecp5/archdefs.h b/ecp5/archdefs.h
index 9428960c..bfc5769b 100644
--- a/ecp5/archdefs.h
+++ b/ecp5/archdefs.h
@@ -158,6 +158,7 @@ struct ArchCellInfo
     struct
     {
         bool using_dff;
+        bool has_l6mux;
         IdString clk_sig, lsr_sig, clkmux, lsrmux, srmode;
     } sliceInfo;
 };
diff --git a/ecp5/pack.cc b/ecp5/pack.cc
index b3f19327..08969f87 100644
--- a/ecp5/pack.cc
+++ b/ecp5/pack.cc
@@ -435,7 +435,6 @@ class Ecp5Packer
                 replace_port(ci, ctx->id("SD"), slice1, id_M1);
                 replace_port(ci, ctx->id("Z"), slice1, id_OFX1);
                 slice0->constr_z = 1;
-                slice0->constr_abs_z = true;
                 slice0->constr_x = 0;
                 slice0->constr_y = 0;
                 slice0->constr_parent = slice1;
@@ -1294,6 +1293,10 @@ void Arch::assignArchInfo()
             ci->sliceInfo.clkmux = id(str_or_default(ci->params, id_CLKMUX, "CLK"));
             ci->sliceInfo.lsrmux = id(str_or_default(ci->params, id_LSRMUX, "LSR"));
             ci->sliceInfo.srmode = id(str_or_default(ci->params, id_SRMODE, "LSR_OVER_CE"));
+            ci->sliceInfo.has_l6mux = false;
+            if (ci->ports.count(id_FXA) && ci->ports[id_FXA].net != nullptr &&
+                ci->ports[id_FXA].net->driver.port == id_OFX0)
+                ci->sliceInfo.has_l6mux = true;
         }
     }
 }