From 437f2d58145b069d1c4b4e9628f774707442ea71 Mon Sep 17 00:00:00 2001
From: kipmacsaigoren <kmacsaigoren@hmc.edu>
Date: Wed, 15 Sep 2021 12:24:24 -0500
Subject: [PATCH] changed priority circuits for synthesis and light cleanup

---
 wally-pipelined/src/mmu/pmpadrdec.sv           |  2 +-
 wally-pipelined/src/mmu/priorityonehot.sv      | 17 ++++++++++-------
 wally-pipelined/src/mmu/prioritythermometer.sv |  8 ++++++--
 3 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/wally-pipelined/src/mmu/pmpadrdec.sv b/wally-pipelined/src/mmu/pmpadrdec.sv
index 618167827..9fe28b261 100644
--- a/wally-pipelined/src/mmu/pmpadrdec.sv
+++ b/wally-pipelined/src/mmu/pmpadrdec.sv
@@ -82,7 +82,7 @@ module pmpadrdec (
   assign NAMask[1:0] = {2'b11};
 
   prioritythemometer #(`PA_BITS-2) namaskgen(
-    .a({PMPAdr[`PA_BITS-4:0], (AdrMode == NAPOT)}),
+    .a({~PMPAdr[`PA_BITS-4:0], (AdrMode == NAPOT)}), // *** confusing bit bussing to match the logic for the inside of the thermometer.
     .y(NAMask[`PA_BITS-1:2]));
 
   assign NAMatch = &((PhysicalAddress ~^ CurrentAdrFull) | NAMask);
diff --git a/wally-pipelined/src/mmu/priorityonehot.sv b/wally-pipelined/src/mmu/priorityonehot.sv
index 7a17f8d28..f02f8ccc5 100644
--- a/wally-pipelined/src/mmu/priorityonehot.sv
+++ b/wally-pipelined/src/mmu/priorityonehot.sv
@@ -40,13 +40,16 @@ module priorityonehot #(parameter ENTRIES = 8) (
   logic [ENTRIES-1:0] nolower;
 
   // generate thermometer code mask
-  genvar i;
-  generate
-    assign nolower[0] = 1'b1;
-    for (i=1; i<ENTRIES; i++) begin:therm
-      assign nolower[i] = nolower[i-1] & ~a[i-1];
-    end
-  endgenerate
+  prioritythemometer #(ENTRIES) maskgen(.a({a[ENTRIES-2:0], 1'b1}), .y(nolower));
+  // genvar i;
+  // generate
+  //   assign nolower[0] = 1'b1;
+  //   for (i=1; i<ENTRIES; i++) begin:therm
+  //     assign nolower[i] = nolower[i-1] & ~a[i-1];
+  //   end
+  // endgenerate
+  // *** replace mask generation logic ^^^ with priority thermometer
+
 
   assign y = a & nolower;
 
diff --git a/wally-pipelined/src/mmu/prioritythermometer.sv b/wally-pipelined/src/mmu/prioritythermometer.sv
index a6374579c..a3eab7e43 100644
--- a/wally-pipelined/src/mmu/prioritythermometer.sv
+++ b/wally-pipelined/src/mmu/prioritythermometer.sv
@@ -37,16 +37,20 @@ module prioritythemometer #(parameter N = 8) (
   output logic  [N-1:0] y
 );
 
+// Carefully crafted so design compiler would synthesize into a fast tree structure
+//  Rather than linear.
 
   // generate thermometer code mask
   genvar i;
   generate
     assign y[0] = a[0];
-    for (i=1; i<N; i++) begin
-      assign y[i] = y[i-1] & a[i];
+    for (i=1; i<N; i++) begin:therm
+      assign y[i] = y[i-1] & ~a[i]; // *** made to be the same as onehot (without the inverter) to see if the probelme is something weird with synthesis
+      // assign y[i] = y[i-1] & a[i];
     end
   endgenerate
 
+
 endmodule