From 288f0c976be58cd38c6b0e851fee0fbdf5cd9ce8 Mon Sep 17 00:00:00 2001
From: Blaise Tine <tinebp@hotmail.com>
Date: Tue, 15 Jun 2021 16:06:54 -0400
Subject: [PATCH] fix split/join hardware

---
 hw/rtl/VX_warp_sched.v | 43 ++++++++++++++++++++----------------------
 1 file changed, 20 insertions(+), 23 deletions(-)

diff --git a/hw/rtl/VX_warp_sched.v b/hw/rtl/VX_warp_sched.v
index 438ddb0b..03b8a9ce 100644
--- a/hw/rtl/VX_warp_sched.v
+++ b/hw/rtl/VX_warp_sched.v
@@ -21,7 +21,7 @@ module VX_warp_sched #(
 
     `UNUSED_PARAM (CORE_ID)
 
-    wire                    join_fall;
+    wire                    join_else;
     wire [31:0]             join_pc;
     wire [`NUM_THREADS-1:0] join_tm;
 
@@ -45,8 +45,6 @@ module VX_warp_sched #(
     reg [`NW_BITS-1:0]      scheduled_warp;
     wire                    warp_scheduled;
 
-    reg didnt_split;   
-
     wire ifetch_rsp_fire = ifetch_rsp_if.valid && ifetch_rsp_if.ready;    
 
     always @(*) begin
@@ -82,7 +80,6 @@ module VX_warp_sched #(
             schedule_table[0] <= 1; // set first warp as ready
             thread_masks[0]   <= 1; // Activating first thread in first warp
             stalled_warps     <= 0;
-            didnt_split       <= 0;
             fetch_lock        <= 0;      
             
             for (integer i = 1; i < `NUM_WARPS; i++) begin
@@ -107,19 +104,10 @@ module VX_warp_sched #(
             end else if (warp_ctl_if.valid && warp_ctl_if.tmc.valid) begin
                 thread_masks[warp_ctl_if.wid] <= warp_ctl_if.tmc.tmask;
                 stalled_warps[warp_ctl_if.wid] <= 0;
-            end else if (join_if.valid && !didnt_split) begin
-                if (!join_fall) begin
-                    warp_pcs[join_if.wid] <= join_pc;
-                end
-                thread_masks[join_if.wid] <= join_tm;
-                didnt_split <= 0;
             end else if (warp_ctl_if.valid && warp_ctl_if.split.valid) begin
                 stalled_warps[warp_ctl_if.wid] <= 0;
                 if (warp_ctl_if.split.diverged) begin
                     thread_masks[warp_ctl_if.wid] <= warp_ctl_if.split.then_mask;
-                    didnt_split <= 0;
-                end else begin
-                    didnt_split <= 1;
                 end
             end          
 
@@ -150,6 +138,14 @@ module VX_warp_sched #(
                 warp_pcs[ifetch_rsp_if.wid] <= ifetch_rsp_if.PC + 4;
             end
 
+            // join handling
+            if (join_if.valid) begin
+                if (join_else) begin
+                    warp_pcs[join_if.wid] <= join_pc;
+                end
+                thread_masks[join_if.wid] <= join_tm;
+            end
+
             active_warps <= active_warps_n;
 
             // reset 'schedule_table' when it goes to zero
@@ -174,22 +170,21 @@ module VX_warp_sched #(
         end
     end
 
-    // split/join stack management
+    // split/join stack management    
 
     wire [(1+32+`NUM_THREADS-1):0] ipdom [`NUM_WARPS-1:0];
-    wire [(1+32+`NUM_THREADS-1):0] q1 = {1'b1, 32'b0,                thread_masks[warp_ctl_if.wid]};
-    wire [(1+32+`NUM_THREADS-1):0] q2 = {1'b0, warp_ctl_if.split.pc, warp_ctl_if.split.else_mask};
-
-    assign {join_fall, join_pc, join_tm} = ipdom [join_if.wid];
-
+    
     for (genvar i = 0; i < `NUM_WARPS; i++) begin
         wire push = warp_ctl_if.valid 
-                 && warp_ctl_if.split.valid 
-                 && warp_ctl_if.split.diverged 
+                 && warp_ctl_if.split.valid
                  && (i == warp_ctl_if.wid);
 
         wire pop = join_if.valid && (i == join_if.wid);
 
+        wire [`NUM_THREADS-1:0] else_mask = warp_ctl_if.split.diverged ? warp_ctl_if.split.else_mask : thread_masks[warp_ctl_if.wid];
+        wire [(1+32+`NUM_THREADS-1):0] q_end  = {1'b0, 32'b0,                thread_masks[warp_ctl_if.wid]};
+        wire [(1+32+`NUM_THREADS-1):0] q_else = {1'b1, warp_ctl_if.split.pc, else_mask};
+
         VX_ipdom_stack #(
             .WIDTH (1+32+`NUM_THREADS), 
             .DEPTH (2 ** (`NT_BITS+1))
@@ -198,14 +193,16 @@ module VX_warp_sched #(
             .reset (reset),
             .push  (push),
             .pop   (pop),
-            .q1    (q1),
-            .q2    (q2),
+            .q1    (q_end),
+            .q2    (q_else),
             .d     (ipdom[i]),
             `UNUSED_PIN (empty),
             `UNUSED_PIN (full)
         );
     end
 
+    assign {join_else, join_pc, join_tm} = ipdom [join_if.wid];
+
     // calculate next warp schedule
 
     reg [`NUM_THREADS-1:0] thread_mask;